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Puerperal mastitis requiring hospitalization during a nine-year period
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OBSTETRICS
Puerperal mastitis requiring hospitalization during a nine-year period I-Wen Lee, MD; Lin Kang, MD; Hui-Ping Hsu, MD; Pao-Lin Kuo, MD; Chia-Ming Chang, MD OBJECTIVES: To review the clinical and microbiologic features of isolates among patients with puerperal mastitis requiring hospitalization. STUDY DESIGN: Between January 2000 and December 2008, postpartum patients who were hospitalized for mastitis were enrolled. The clinical characteristics, microbiologic results, management, and outcomes were reviewed. RESULTS: One hundred twenty-seven cases were enrolled. Seventy-
six patients (59.9%) underwent incision and drainage for abscess drainage, all of whom discontinued breastfeeding. Staphylococcus aureus and coagulase-negative staphylococci were the most common
isolates. Among 81 isolates of S aureus, 52 (64.2%) were resistant to oxacillin. Patients undergoing incision and drainage were more likely to discontinue breastfeeding, had a longer duration of symptoms, a longer hospitalization, a higher platelet count and higher rates of infection caused by S aureus and oxacillin-resistant S aureus. CONCLUSION: Oxacillin-resistant S aureus has emerged in patients
with puerperal mastitis during the past decade, and often necessitates incision and drainage, which results in discontinuation of breastfeeding. Key words: methicillin-resistant, oxacillin resistance, puerperal mastitis, staphylococcus, Staphylococcus aureus
Cite this article as: Lee I-W, Kang L, Hsu H-P, et al. Puerperal mastitis requiring hospitalization during a nine-year period. Am J Obstet Gynecol 2010;203:332.e1-6.
P
uerperal mastitis, an acute inflammation of the interlobular connective tissue within the mammary glands, frequently occurs among breastfeeding women, and potentially has a negative impact on continued breastfeeding.1 Up to 25% of parturients have experienced at least 1 episode of mastitis and 4-8.5% of parturients have had recurrent episodes of mastitis.2,3 Mastitis occurs most commonly during the first 3 months after delivery. Symptoms usually begin as malaise and fever, followed by erythema and tenderness in the affected breast. The triad of unilateral breast pain, erythema, and fever in a breastfeeding woman is a classic presentation, but variations exist.3 Supportive care, such as hot compresses, breast masFrom the Departments of Obstetrics and Gynecology (Drs Lee, Kang, and Kuo), Surgery (Dr Hsu), and Internal Medicine (Dr Chang), National Cheng Kung University Hospital, and the Department of Medicine, National Cheng Kung University Medical College (all authors), Tainan, Taiwan. Received Dec. 3, 2009; revised Feb. 21, 2010; accepted May 5, 2010. Reprints not available from the authors. 0002-9378/$36.00 © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.05.012
332.e1
sage, a change in breastfeeding patterns, and a breast pump, are often advised.3,4 Few patients require inpatient treatment, most often because of refractory breast engorgement, persistent fever, or abscess formation.3 The incidence of puerperal mastitis requiring hospitalization and mastitis with abscess formation is 6.7 and 2.6 per 10,000 deliveries, respectively.5 As with other soft tissue infections, mastitis is often caused by Staphylococcus aureus, coagulase-negative staphylococci (CNS), Streptococcus species, and Escherichia coli.4 In the past, staphylococci were usually susceptible to oxacillin or methicillin;6 however, it has recently been reported that approximately 60% of staphylococci (nosocomial or community acquired) are resistant to oxacillin.6,7 A recent study on puerperal mastitis has shown oxacillin-resistant S aureus (ORSA) to be a primary pathogen,8 thus often necessitating surgical incision and drainage (I&D). The morbidity and adverse effects of surgical I&D on breastfeeding, however, have not been thoroughly evaluated. The purpose of this study was to describe the presentation, management, and outcomes (including continued breastfeeding) of patients with puerperal mastitis requiring hospitalization during a 9-year period. We also reviewed the
American Journal of Obstetrics & Gynecology OCTOBER 2010
cultures of the specimens obtained from these patients to update the microbiologic profile and to elucidate the antimicrobial susceptibilities in the era of emerging bacterial resistance.
M ATERIALS AND M ETHODS Between Jan. 1, 2000, and Dec. 31, 2008, parturients who were hospitalized for puerperal mastitis at a tertiary medical center in southern Taiwan were enrolled. Cases were identified based on a discharge diagnosis of mastitis and screened by a history of nursing or a recent delivery before admission. Mastitis was diagnosed by clinical presentation, such as unilateral breast tenderness and erythema, fever, or a palpable breast abscess. The demographic characteristics, clinical features, and microbiologic findings of specimens were recorded by chart review. Cultures of milk and abscesses were collected with sterile dacron swabs. Blood cultures were obtained during a febrile episode. Specimens were transported and processed using standardized methods. The identification of microorganisms was based on the morphology of colonies and biochemistry reactions. Antimicrobial susceptibility was determined using disk diffusion methods, according to the description by the Clinical and Laboratory Standard Institute.9
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TABLE 1
Clinical features of 127 patients with puerperal mastitis Characteristics
n
Range
Age, y
29.2 ⫾ 4.39
Primiparas
73 (64.6%)
Duration of symptoms, d
11.58 ⫾ 18.94
Highest temperature, C
38.14 ⫾ 1.05
(19–40)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
(1–30)
.............................................................................................................................................................................................................................................. o
(36.0–40.3)
..............................................................................................................................................................................................................................................
Postpartum period, d (124 patients)
.....................................................................................................................................................................................................................................
⬍30
31 (25.0%)
30-60
52 (41.9%)
69-90
29 (23.4%)
90-180
11 (8.9%)
⬎180
1 (0.8%)
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Delivery method (79 cases)
.....................................................................................................................................................................................................................................
Cesarean section
23 (29.1%)
Vaginal delivery
56 (70.9%)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Feeding methods (94 cases)
.....................................................................................................................................................................................................................................
Direct feeding
59 (62.7%)
.....................................................................................................................................................................................................................................
Pumping for bottle feeding
14 (14.8%)
Combined
13 (13.8%)
Weaning
8 (8.5%)
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Intrapartum treatment with antimicrobials
80 (63%)
Discontinued breastfeeding
93 (73.2%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
Laboratory data
..................................................................................................................................................................................................................................... 3
Leukocyte count (10 /L)
12.27 ⫾ 4.75
(4.2–5.2)
............................................................................................................................................................................................................................
Bands, %
4.99 ⫾ 7.69
(0–38)
71.92 ⫾ 13.40
(31–94)
............................................................................................................................................................................................................................
Segments, %
..................................................................................................................................................................................................................................... 3
Platelet count (10 /L)
301.35 ⫾ 106.97
(14.5–544)
.....................................................................................................................................................................................................................................
Hemoglobin, g/dL
11.90 ⫾ 1.36
(7.5–15.4)
C-reactive protein, g/mL
64.63 ⫾ 56.87
(7–303)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Intervention
.....................................................................................................................................................................................................................................
No surgical intervention
47 (37.0%)
Incision and drainage
76 (59.9%)
..................................................................................................................................................................................................................................... .....................................................................................................................................................................................................................................
Aspiration
4 (3.2%)
..............................................................................................................................................................................................................................................
Duration of hospitalization, d
7.69 ⫾ 6.04
(1–34)
..............................................................................................................................................................................................................................................
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
Data analysis was performed using the Statistical Package for the Social Sciences for Windows (SPSSWIN, version 13.0; SPSS, Inc, Chicago, IL). Continuous data, expressed as the mean ⫾ standard deviation, were compared by the Student t test or Mann-Whitney U test. Categorical variables, expressed as numbers and percentages, were compared by the 2 or
Fisher’s exact test. The level of statistical significance was set at .05.
R ESULTS One hundred twenty-seven charts were available for review. There were 6 cases each year from 2000-2002, 11 in 2003, 16 in 2004, 13 in 2005, 26 in 2006, 22 in
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2007, and 21 in 2008. The crude incidence increased from ⬍0.5% in 2000 to ⬎2.0% after 2006. The clinical features of the 127 cases are summarized in Table 1. More than 90% of cases occurred during the first 3 months after delivery, with the highest occurrence during the second month after delivery (52 cases; 41.9%). Three patients had comorbidities; specifically, 1 patient had pneumonia during pregnancy and was hospitalized during the 28th gestational week, but recovered before delivery, 1 patient had idiopathic thrombocytopenia, and 1 patient had a history of systemic lupus erythematosus. Obstetric conditions or complications were recorded in 13 patients, including pregnancy-induced hypertension in 3 patients, postpartum hemorrhage in 2 patients, a twin pregnancy in 2 patients, preterm premature rupture of membranes in 2 patients, and placenta previa, antepartum hemorrhage, a cervical laceration, and a fourthdegree perineal laceration, each occurring in 1 patient. Seventy-six patients (59.9%) underwent I&D for abscess drainage; all the patients discontinued breastfeeding. Four patients underwent needle aspiration and the remaining 47 patients received antimicrobial therapy only. Excluding the 4 patients who underwent needle aspiration, a comparison of the clinical characteristics between patients with and without I&D is summarized in Table 2. Compared with patients who did not have an I&D, those who had an I&D had a longer duration of symptoms, a higher rate of discontinued breastfeeding, a lower peak body temperature, a higher platelet count, a higher rate of cultureproven S aureus and ORSA infection, and a longer hospitalization. Among 101 patients with the documented use of antimicrobial agents before admission, pathogens were identified in 99 cultures. Among 38 patients who received effective antimicrobial agents against the isolated pathogens, 21 (55.3%) underwent surgical intervention. In contrast, 46 (75.4%) of the 61 patients who received ineffective antimicrobial agents required surgical intervention (P ⫽ .062).
OCTOBER 2010 American Journal of Obstetrics & Gynecology
332.e2
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Obstetrics
Ninety-three patients discontinued breastfeeding after hospitalization. All 76 patients who had an I&D chose early weaning and therefore discontinued breastfeeding, whereas 17 (36.2%) of 47 patients who did not need surgical intervention had early weaning (P ⬍ .0001). Specimens obtained from 122 patients were sent for culture. Twelve patients had cultures of the peripheral blood only. Thirty-five patients only had cultures of milk, which were obtained by manual expression. In the remaining 75 patients, the specimens sent for culture, included pus, abscess, or drainage. The cultures of specimens yielded no growth of bacteria in 14 patients. The microorganisms isolated from 108 patients with positive cultures of bacteria are summarized in Table 3. Cultures from 71 patients yielded growth of monomicrobial pathogens, which were usually isolated from the abscess or drainage specimens (82.9%). Polymicrobial pathogens were isolated in 37 patients (77 isolates), most of which were from milk. Among the patients with polymicrobial isolates, each patient had at least 1 strain of staphylococci isolated. Staphylococcal strains, including S aureus and coagulase-negative staphylococci (CNS), were the most common isolates from milk or pus obtained from 100 patients (100/127; 78.7%). S aureus was the main pathogen in 80 patients (80/127; 63%); 52 (64.2%) of 81 S aureus isolates were resistant to oxacillin. One case had mixed growth of both oxacillinsusceptible and oxacillin-resistant stains of S aureus. Compared with patients caused by non-ORSA mastitis, those with ORSA mastitis were associated with a higher rate of I&D (41/51; 80.4% vs 35/ 76; 46.1%; P ⬍ .001). All the ORSA isolates were susceptible to vancomycin, teicoplanin, linezolid, fusidic acid, and 1 isolate of ORSA was resistant to trimethoprim/sulfamethoxazole (TMP/ SMZ). Among patients with ORSA mastitis, there were only 5 cases that had appropriate antimicrobial agents use at admission. Symptoms in 4 patients subsided under appropriate antimicrobial treatment without I&D. The second most common pathogen isolated was CNS, which was the monomicrobial pathogen isolated from 13 332.e3
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TABLE 2
Comparison of clinical characteristics between patients with and without I&D Characteristics
No I&D (nⴝ47) 29.12 ⫾ 4.35
Age, y
I&D (nⴝ76) 29.30 ⫾ 4.69
P value .833
..............................................................................................................................................................................................................................................
Parity (121 cases)
.....................................................................................................................................................................................................................................
Primipara
29 (61.7%)
Multipara
16 (34.1%)
41 (54.0%)
.274
.....................................................................................................................................................................................................................................
35 (46.0%)
..............................................................................................................................................................................................................................................
Duration of symptoms, d
2.90 ⫾ 2.48
16.83 ⫾ 22.73
⬍ .001
Highest temperature, C
39.04 ⫾ 0.68
37.68 ⫾ 0.84
⬍ .001
Postpartum period, d
44.56 ⫾ 62.57
76.90 ⫾ 82.41
.............................................................................................................................................................................................................................................. o .............................................................................................................................................................................................................................................. a
.037
..............................................................................................................................................................................................................................................
Delivery method (79 cases)
.625
.....................................................................................................................................................................................................................................
Cesarean section
14 (32.6%)
9 (25%)
Vaginal delivery
29 (67.5%)
27 (75%)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Feeding methods (94 cases)
.....................................................................................................................................................................................................................................
Direct feeding
16 (48.5%)
43 (70.1%)
Pumping then bottle feeding
7 (21.2%)
7 (11.5%)
Combined
9 (27.3%)
10 (16.4%)
Weaning
1 (3.0%)
1 (1.6%)
Discontinued breastfeeding
17 (60.3%)
76 (100%)
⬍ .001
Intrapartum treatment with antimicrobials
19 (40.4%)
14 (18.4%)
.862
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
Laboratory data
..................................................................................................................................................................................................................................... 3
Leukocyte count (10 /L)
13.07 ⫾ 24.65
12.00 ⫾ 4.98
.249
7.75 ⫾ 9.42
3.35 ⫾ 5.76
.008
71.70 ⫾ 18.39
70.95 ⫾ 13.94
.817
C-reactive protein, g/mL
69.38 ⫾ 60.03
59.28 ⫾ 53.69
.413
Hemoglobin, g/dL
14.86 ⫾ 17.75
11.85 ⫾ 1.19
.315
269.60 ⫾ 89.18
316.29 ⫾ 114.02
.032
............................................................................................................................................................................................................................
Bands, %
............................................................................................................................................................................................................................
Segments, %
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... 3
Platelet count (10 /L)
..............................................................................................................................................................................................................................................
Staphylococcus aureus
19 (40.4%)
61 (80.3%)
⬍ .001
Oxacillin-resistant S aureus
10 (21.3%)
42 (55.3%)
⬍ .001
Effective antimicrobials before admission
15 (31.9%)
22 (29.0%)
.161
Effective antimicrobials after admission
23 (48.9%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
44 (57.9%)
.444
..............................................................................................................................................................................................................................................
Duration of hospitalization, d
4.57 ⫾ 1.90
9.94 ⫾ 6.11
⬍ .001
..............................................................................................................................................................................................................................................
I&D, incision and drainage. a
Four patients who received aspiration only are not included in this table.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
patients. Twelve (92.3%) monomicrobial CNS isolates were resistant to oxacillin. Among all 38 CNS isolates, 15 (39.5%) isolates were susceptible to oxacillin. The Figure shows secular trends of puerperal mastitis caused by staphylococci during the study period.
American Journal of Obstetrics & Gynecology OCTOBER 2010
C OMMENT Since 2000, the “baby friendly hospital initiate policy” has been promoted and the prevalence of breastfeeding immediately postpartum and 6 months postpartum among new mothers has increased. In Taiwan, the prevalence of exclusive
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TABLE 3
Microorganisms isolated from 108 patients with positive cultures of bacteria Specimens Microorganisms
Total cases
Monomicrobial (cases)
71
Abscess/ drainage
Blood
9
61
1
Milk
.....................................................................................................................................................................................................................................
Staphylococcus aureus (isolates)
56
7
49
Oxacillin-resistant
37
5
32
Oxacillin-susceptible
19
2
17
13
2
10
1
Oxacillin-resistant
12
1
10
1
Oxacillin-susceptible
1
1
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
CNS
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
Citrobacter koseri
1
1
1
1
...........................................................................................................................................................................................................................
Anaerobic Gram-positive bacilli
..............................................................................................................................................................................................................................................
Polymicrobial (cases)
37
25
12
24
15
9
Oxacillin-resistant
15
10
5
Oxacillin-susceptible
10
6
4
..................................................................................................................................................................................................................................... a
S aureus (isolates)
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
CNS
25
19
6
Oxacillin-resistant
11
9
2
Oxacillin-susceptible
14
14
8
8
Viridans streptococcus
2
2
S pneumoniae
1
1
Enterococcus
3
2
Propionibacterium
1
Klebsiella pneumoniae
3
K oxytoca
1
Serratia marcescens
1
1
Acinetobacter junii
1
1
A baumannii
1
1
C koseri
1
1
Gram-positive bacilli
3
3
Bacillus spp
2
2
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
Group B Streptococcus
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .....................................................................................................................................................................................................................................
1
.....................................................................................................................................................................................................................................
1
.....................................................................................................................................................................................................................................
3
.....................................................................................................................................................................................................................................
1
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .............................................................................................................................................................................................................................................. a
One case had mixed growth of both oxacillin-susceptible and -resistant stains of S aureus.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
breastfeeding in the first postpartum month increased from 5.4% in 1989 to 22.3% in 2004,10 or from 33.2% in 2004 to 54.3% in 2008, according to the official report by the Taiwan Bureau of Health Promotion.11 The possible adverse effect of increased breastfeeding is the increased rate of puerperal mastitis.12 Not surprisingly, the incidence of
mastitis requiring inpatient therapy increased in parallel with the prevalence of breastfeeding in our study. The bacteria cultured from milk and/or pus were mainly staphylococci. Of note, ORSA has emerged as a main pathogen. Several cases of puerperal mastitis caused by ORSA among young and healthy women without traditional
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risk factors have been reported in the past few years.13-15 In a study involving patients with puerperal mastitis requiring hospitalization, 59% of cultures from cases with breast abscesses were shown to be ORSA,8 which is compatible with our study. Because of cross-resistance, ORSA is often resistant to all -lactam agents, even in combination with a -lactamase inhibitor.16 Fortunately, community-acquired ORSA strains are usually susceptible to the oral non--lactam agents, such as TMP/SMZ and fusidic acid. Oxacillin resistance has emerged not only in S aureus. In the current study, ⬎90% of monomicrobial CNS isolates were also resistant to oxacillin. There is evidence of horizontal transfer of the methicillin-resistance island of the staphylococcal cassettes chromosome (SCCmec) between staphylococcal species,17 which implies that CNS may serve as an environmental reservoir for the spread of resistance genes encoded in SCCmec to S aureus. Patients undergoing I&D for abscess drainage were associated with more symptomatic days and hospitalization, a higher rate of discontinued breastfeeding, a higher rate of isolation of S aureus and ORSA, and a higher platelet count. Reactive thrombocytosis can occur in patients with severe infections and is associated with abscess formation.18 Thrombocytosis may result from elevated levels of endogenous thrombopoietin, interleukin-6 or other cytokines, and catecholamines that are produced in inflammatory, infectious, or neoplastic conditions or in situations of stress.19 A longer duration of symptoms and hospitalization may be related to the increasing severity associated with abscess formation, and more complicated postsurgery care after I&D. S aureus infection is associated with abscess formation.20,21 The pyogenic property of S aureus is not changed in ORSA.21,22 Therefore, our study also showed that patients caused by ORSA mastitis were associated with a higher rate of I&D in comparison with those caused by non-ORSA mastitis. The incidence of mastitis was highest in the first few weeks postpartum and 73.2% of parturients discontinued
OCTOBER 2010 American Journal of Obstetrics & Gynecology
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FIGURE
Secular trends of puerperal mastitis caused by staphylococci during 2000-2008 OSSA
CNS
Incidence 3.00%
25
2.50%
20
2.00%
15
1.50%
10
1.00%
5
0.50%
0
Incidence
case number
ORSA 30
0.00%
2000
2001
2002
2003
2004
2005
2006
2007
2008
Incidence: annual number of hospitalized cases of puerperal mastitis divided by number of deliveries per year at the study hospital. CNS, coagulase-negative staphylococci; ORSA, oxacillin-resistant Staphylococcus aureus; OSSA, oxacillin-susceptible Staphylococcus aureus.
der inappropriate antimicrobial therapy, our study showed only 1 case with appropriate anti-ORSA therapy required I&D eventually. To elucidate the impact of appropriate antimicrobial treatment on ORSA mastitis needs further study. In addition, molecular typing, which could have possibly provided more information about the isolates, was not performed. In conclusion, cases of mastitis increased with the prevalence of breastfeeding in the recent 9 years. Abscess formation may necessitate surgical intervention, but leads to early weaning from breastfeeding and longer hospital stays. For a local liquefied abscess, ultrasoundguided aspiration along with adequate antimicrobial treatment is the preferred option. Oxacillin resistance has emerged in the Gram-positive cocci isolated from milk and abscesses. Empiric antimicrobial therapy to cover oxacillin-resistant staphylococci is needed among patients who fail to respond to -lactam f agents.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
REFERENCES
breastfeeding. Once patients had an I&D and began regular wet dressings, the morbidity and subsequent hospitalization often led to discontinuation of breastfeeding, even though there is consensus that lactation should be continued.2 In the current study, all 76 cases undergoing I&D discontinued breastfeeding, whereas the 4 cases who had an aspiration of abscess continued breastfeeding (100% vs 0%; P ⬍ .001). Although not proven, it appears that an invasive intervention of a breast abscess decreases the rate of breastfeeding. In addition to the wound pain, patients might choose to discontinue breastfeeding because of a disconnection with their infants, fear of residual medication in milk, the potential hazard of bacteria-containing milk to infants, or following the recommendations of health care givers. Nevertheless, prior studies have shown that there are no complications associated with continued breastfeeding, even in the presence of a breast abscess.23,24 Although there has been a case report of staphylococcal scalded skin syndrome in 332.e5
a breastfed infant whose mother had mastitis or a breast abscess, the infant may have been infected via close contact rather than breastfeeding alone.25 There were several limitations to the current study. First, because of the study’s retrospective nature, clinical data in the medical records may have been incomplete. Second, our findings are not generalizable to all patients with puerperal mastitis because empirically treated mastitis might be cured without collecting a culture or hospitalization, thereby overestimating the burden of disease. Resistant pathogens tend to survive among patients who responded poorly to empiric antimicrobial therapy. Perhaps in Taiwan, the clinicians are used to prescribing empiric antimicrobials, which do not cover ORSA, for example, -lactam agents for patients with mastitis, we found only 5 cases with ORSA mastitis had appropriate antimicrobial agents use at admission. Although previous study reported that no treatment failure among 15 of 16 women with culture-proven ORSA mastitis un-
American Journal of Obstetrics & Gynecology OCTOBER 2010
1. Schwartz K, D’Arcy HJ, Gillespie B, Bobo J, Longeway M, Foxman B. Factors associated with weaning in the first 3 months postpartum. J Fam Pract 2002;51:439-44. 2. Foxman B, D’Arcy H, Gillespie B, Bobo JK, Schwartz K. Lactation mastitis: occurrence and medical management among 946 breastfeeding women in the United States. Am J Epidemiol 2002;155:103-14. 3. Barbosa-Cesnik C, Schwartz K, Foxman B. Lactation mastitis. JAMA 2003;289:1609-12. 4. World Health Organization. Mastitis: causes and management. WHO/FCH/CAH/00.13. Geneva: WHO; 2000. 5. Stafford I, Hernandez J, Laibl V, Sheffield J, Roberts S, Wendel G Jr. Community-acquired methicillin-resistant Staphylococcus aureus among patients with puerperal mastitis requiring hospitalization. Obstet Gynecol 2008;112: 533-7. 6. Bal AM, Gould IM. Antibiotic resistance in Staphylococcus aureus and its relevance in therapy. Expert Opin Pharmacother 2005;6: 2257-69. 7. Tillotson GS, Draghi DC, Sahm DF, Tomfohrde KM, Del Fabro T, Critchley IA. Susceptibility of Staphylococcus aureus isolated from skin and wound infections in the United States 2005-07: laboratory-based surveillance study. J Antimicrob Chemother 2008;62:109-15. 8. Reddy P, Qi C, Zembower T, Noskin GA, Bolon M. Postpartum mastitis and community-
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www.AJOG.org acquired methicillin-resistant Staphylococcus aureus. Emerg Infect Dis 2007;13:298-301. 9. Clinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing. 16th informational supplement. CLSI document M100-S16. Wayne, PA: Clinical and Laboratory Standards Institute; 2006. 10. Chien LY, Chu KH, Tai CJ, Lin CY. National prevalence of breastfeeding in Taiwan. J Hum Lact 2005;21:338-44. 11. Bureau of Health Promotion, Department of Health, Taiwan. Prevalence of exclusive breastfeeding in the first postpartum month (in Chinese). Available at: http://www.bhp.doh.gov.tw/ BHPnet/Portal/Them_Show.aspx?Subject⫽ 200712250063&Class⫽2&No⫽200712250332. Accessed Feb. 5, 2010. 12. Lawrence RA. Mastitis while breastfeeding: old theories and new evidence. Am J Epidemiol 2002;15;155:115-6. 13. Wilson-Clay B. Case report of methicillinresistant Staphylococcus aureus (MRSA) mastitis with abscess formation in a breastfeeding woman. J Hum Lact 2008;24:326-9.
14. Montalto M, Lui B. MRSA as a cause of postpartum breast abscess in infant and mother. J Hum Lact 2009;25:448-50. 15. Amir L. Breastfeeding and Staphylococcus aureus: three case reports. Breastfeed Rev 2002;10:15-8. 16. Moreillon P, Que YA, Glauser MP. Staphylococcus aureus. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas and Bennett’s principles and practice of infectious diseases, 6th ed. Philadelphia: Churchill Livingstone; 2005:2321-51. 17. Hanssen AM, Kjeldsen G, Sollid JU. Local variants of staphylococcal cassette chromosome mec in sporadic methicillin-resistant Staphylococcus aureus and methicillin-resistant coagulase-negative staphylococci: evidence of horizontal gene transfer? Antimicrob Agents Chemother 2004;48:285-96. 18. Gofrit ON, Shapiro A, Rund D, et al. Thrombocytosis accompanying urinary tract infection suggests obstruction or abscess. Am J Emerg Med 2006;24:118-21. 19. Schafer AI. Thrombocytosis. N Engl J Med 2004;350:1211-9.
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20. Tacconelli E, Tumbarello M, Cauda R. Staphylococcus aureus infections. N Engl J Med 1998;339:2026-7. 21. Cheung AL, Bayer AS, Zhang G, Gresham H, Xiong YQ. Regulation of virulence determinants in vitro and in vivo in Staphylococcus aureus. FEMS Immunol Med Microbiol 2004; 40:1-9. 22. Loughman JA, Fritz SA, Storch GA, Hunstad DA. Virulence gene expression in human community-acquired Staphylococcus aureus infection. J Infect Dis 2009;199:294-301. 23. Marshall BR, Hepper JK, Zirbel CC. Sporadic puerperal mastitis. An infection that need not interrupt lactation. JAMA 1975;233: 1377-9. 24. Niebyl JR, Spence MR, Parmley TH. Sporadic (nonepidemic) puerperal mastitis. J Reprod Med 1978;20:97-100. 25. Raymond J, Bingen E, Brahimi N, et al. Staphylococcal scalded skin syndrome in a neonate. Eur J Clin Microbiol Infect Dis 1997; 16:453-4.
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OBSTETRICS
Puerperal mastitis requiring hospitalization during a nine-year period I-Wen Lee, MD; Lin Kang, MD; Hui-Ping Hsu, MD; Pao-Lin Kuo, MD; Chia-Ming Chang, MD OBJECTIVES: To review the clinical and microbiologic features of isolates among patients with puerperal mastitis requiring hospitalization. STUDY DESIGN: Between January 2000 and December 2008, postpartum patients who were hospitalized for mastitis were enrolled. The clinical characteristics, microbiologic results, management, and outcomes were reviewed. RESULTS: One hundred twenty-seven cases were enrolled. Seventy-
six patients (59.9%) underwent incision and drainage for abscess drainage, all of whom discontinued breastfeeding. Staphylococcus aureus and coagulase-negative staphylococci were the most common
isolates. Among 81 isolates of S aureus, 52 (64.2%) were resistant to oxacillin. Patients undergoing incision and drainage were more likely to discontinue breastfeeding, had a longer duration of symptoms, a longer hospitalization, a higher platelet count and higher rates of infection caused by S aureus and oxacillin-resistant S aureus. CONCLUSION: Oxacillin-resistant S aureus has emerged in patients
with puerperal mastitis during the past decade, and often necessitates incision and drainage, which results in discontinuation of breastfeeding. Key words: methicillin-resistant, oxacillin resistance, puerperal mastitis, staphylococcus, Staphylococcus aureus
Cite this article as: Lee I-W, Kang L, Hsu H-P, et al. Puerperal mastitis requiring hospitalization during a nine-year period. Am J Obstet Gynecol 2010;203:332.e1-6.
P
uerperal mastitis, an acute inflammation of the interlobular connective tissue within the mammary glands, frequently occurs among breastfeeding women, and potentially has a negative impact on continued breastfeeding.1 Up to 25% of parturients have experienced at least 1 episode of mastitis and 4-8.5% of parturients have had recurrent episodes of mastitis.2,3 Mastitis occurs most commonly during the first 3 months after delivery. Symptoms usually begin as malaise and fever, followed by erythema and tenderness in the affected breast. The triad of unilateral breast pain, erythema, and fever in a breastfeeding woman is a classic presentation, but variations exist.3 Supportive care, such as hot compresses, breast masFrom the Departments of Obstetrics and Gynecology (Drs Lee, Kang, and Kuo), Surgery (Dr Hsu), and Internal Medicine (Dr Chang), National Cheng Kung University Hospital, and the Department of Medicine, National Cheng Kung University Medical College (all authors), Tainan, Taiwan. Received Dec. 3, 2009; revised Feb. 21, 2010; accepted May 5, 2010. Reprints not available from the authors. 0002-9378/$36.00 © 2010 Mosby, Inc. All rights reserved. doi: 10.1016/j.ajog.2010.05.012
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sage, a change in breastfeeding patterns, and a breast pump, are often advised.3,4 Few patients require inpatient treatment, most often because of refractory breast engorgement, persistent fever, or abscess formation.3 The incidence of puerperal mastitis requiring hospitalization and mastitis with abscess formation is 6.7 and 2.6 per 10,000 deliveries, respectively.5 As with other soft tissue infections, mastitis is often caused by Staphylococcus aureus, coagulase-negative staphylococci (CNS), Streptococcus species, and Escherichia coli.4 In the past, staphylococci were usually susceptible to oxacillin or methicillin;6 however, it has recently been reported that approximately 60% of staphylococci (nosocomial or community acquired) are resistant to oxacillin.6,7 A recent study on puerperal mastitis has shown oxacillin-resistant S aureus (ORSA) to be a primary pathogen,8 thus often necessitating surgical incision and drainage (I&D). The morbidity and adverse effects of surgical I&D on breastfeeding, however, have not been thoroughly evaluated. The purpose of this study was to describe the presentation, management, and outcomes (including continued breastfeeding) of patients with puerperal mastitis requiring hospitalization during a 9-year period. We also reviewed the
American Journal of Obstetrics & Gynecology OCTOBER 2010
cultures of the specimens obtained from these patients to update the microbiologic profile and to elucidate the antimicrobial susceptibilities in the era of emerging bacterial resistance.
M ATERIALS AND M ETHODS Between Jan. 1, 2000, and Dec. 31, 2008, parturients who were hospitalized for puerperal mastitis at a tertiary medical center in southern Taiwan were enrolled. Cases were identified based on a discharge diagnosis of mastitis and screened by a history of nursing or a recent delivery before admission. Mastitis was diagnosed by clinical presentation, such as unilateral breast tenderness and erythema, fever, or a palpable breast abscess. The demographic characteristics, clinical features, and microbiologic findings of specimens were recorded by chart review. Cultures of milk and abscesses were collected with sterile dacron swabs. Blood cultures were obtained during a febrile episode. Specimens were transported and processed using standardized methods. The identification of microorganisms was based on the morphology of colonies and biochemistry reactions. Antimicrobial susceptibility was determined using disk diffusion methods, according to the description by the Clinical and Laboratory Standard Institute.9
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TABLE 1
Clinical features of 127 patients with puerperal mastitis Characteristics
n
Range
Age, y
29.2 ⫾ 4.39
Primiparas
73 (64.6%)
Duration of symptoms, d
11.58 ⫾ 18.94
Highest temperature, C
38.14 ⫾ 1.05
(19–40)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
(1–30)
.............................................................................................................................................................................................................................................. o
(36.0–40.3)
..............................................................................................................................................................................................................................................
Postpartum period, d (124 patients)
.....................................................................................................................................................................................................................................
⬍30
31 (25.0%)
30-60
52 (41.9%)
69-90
29 (23.4%)
90-180
11 (8.9%)
⬎180
1 (0.8%)
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Delivery method (79 cases)
.....................................................................................................................................................................................................................................
Cesarean section
23 (29.1%)
Vaginal delivery
56 (70.9%)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Feeding methods (94 cases)
.....................................................................................................................................................................................................................................
Direct feeding
59 (62.7%)
.....................................................................................................................................................................................................................................
Pumping for bottle feeding
14 (14.8%)
Combined
13 (13.8%)
Weaning
8 (8.5%)
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Intrapartum treatment with antimicrobials
80 (63%)
Discontinued breastfeeding
93 (73.2%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
Laboratory data
..................................................................................................................................................................................................................................... 3
Leukocyte count (10 /L)
12.27 ⫾ 4.75
(4.2–5.2)
............................................................................................................................................................................................................................
Bands, %
4.99 ⫾ 7.69
(0–38)
71.92 ⫾ 13.40
(31–94)
............................................................................................................................................................................................................................
Segments, %
..................................................................................................................................................................................................................................... 3
Platelet count (10 /L)
301.35 ⫾ 106.97
(14.5–544)
.....................................................................................................................................................................................................................................
Hemoglobin, g/dL
11.90 ⫾ 1.36
(7.5–15.4)
C-reactive protein, g/mL
64.63 ⫾ 56.87
(7–303)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Intervention
.....................................................................................................................................................................................................................................
No surgical intervention
47 (37.0%)
Incision and drainage
76 (59.9%)
..................................................................................................................................................................................................................................... .....................................................................................................................................................................................................................................
Aspiration
4 (3.2%)
..............................................................................................................................................................................................................................................
Duration of hospitalization, d
7.69 ⫾ 6.04
(1–34)
..............................................................................................................................................................................................................................................
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
Data analysis was performed using the Statistical Package for the Social Sciences for Windows (SPSSWIN, version 13.0; SPSS, Inc, Chicago, IL). Continuous data, expressed as the mean ⫾ standard deviation, were compared by the Student t test or Mann-Whitney U test. Categorical variables, expressed as numbers and percentages, were compared by the 2 or
Fisher’s exact test. The level of statistical significance was set at .05.
R ESULTS One hundred twenty-seven charts were available for review. There were 6 cases each year from 2000-2002, 11 in 2003, 16 in 2004, 13 in 2005, 26 in 2006, 22 in
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2007, and 21 in 2008. The crude incidence increased from ⬍0.5% in 2000 to ⬎2.0% after 2006. The clinical features of the 127 cases are summarized in Table 1. More than 90% of cases occurred during the first 3 months after delivery, with the highest occurrence during the second month after delivery (52 cases; 41.9%). Three patients had comorbidities; specifically, 1 patient had pneumonia during pregnancy and was hospitalized during the 28th gestational week, but recovered before delivery, 1 patient had idiopathic thrombocytopenia, and 1 patient had a history of systemic lupus erythematosus. Obstetric conditions or complications were recorded in 13 patients, including pregnancy-induced hypertension in 3 patients, postpartum hemorrhage in 2 patients, a twin pregnancy in 2 patients, preterm premature rupture of membranes in 2 patients, and placenta previa, antepartum hemorrhage, a cervical laceration, and a fourthdegree perineal laceration, each occurring in 1 patient. Seventy-six patients (59.9%) underwent I&D for abscess drainage; all the patients discontinued breastfeeding. Four patients underwent needle aspiration and the remaining 47 patients received antimicrobial therapy only. Excluding the 4 patients who underwent needle aspiration, a comparison of the clinical characteristics between patients with and without I&D is summarized in Table 2. Compared with patients who did not have an I&D, those who had an I&D had a longer duration of symptoms, a higher rate of discontinued breastfeeding, a lower peak body temperature, a higher platelet count, a higher rate of cultureproven S aureus and ORSA infection, and a longer hospitalization. Among 101 patients with the documented use of antimicrobial agents before admission, pathogens were identified in 99 cultures. Among 38 patients who received effective antimicrobial agents against the isolated pathogens, 21 (55.3%) underwent surgical intervention. In contrast, 46 (75.4%) of the 61 patients who received ineffective antimicrobial agents required surgical intervention (P ⫽ .062).
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Ninety-three patients discontinued breastfeeding after hospitalization. All 76 patients who had an I&D chose early weaning and therefore discontinued breastfeeding, whereas 17 (36.2%) of 47 patients who did not need surgical intervention had early weaning (P ⬍ .0001). Specimens obtained from 122 patients were sent for culture. Twelve patients had cultures of the peripheral blood only. Thirty-five patients only had cultures of milk, which were obtained by manual expression. In the remaining 75 patients, the specimens sent for culture, included pus, abscess, or drainage. The cultures of specimens yielded no growth of bacteria in 14 patients. The microorganisms isolated from 108 patients with positive cultures of bacteria are summarized in Table 3. Cultures from 71 patients yielded growth of monomicrobial pathogens, which were usually isolated from the abscess or drainage specimens (82.9%). Polymicrobial pathogens were isolated in 37 patients (77 isolates), most of which were from milk. Among the patients with polymicrobial isolates, each patient had at least 1 strain of staphylococci isolated. Staphylococcal strains, including S aureus and coagulase-negative staphylococci (CNS), were the most common isolates from milk or pus obtained from 100 patients (100/127; 78.7%). S aureus was the main pathogen in 80 patients (80/127; 63%); 52 (64.2%) of 81 S aureus isolates were resistant to oxacillin. One case had mixed growth of both oxacillinsusceptible and oxacillin-resistant stains of S aureus. Compared with patients caused by non-ORSA mastitis, those with ORSA mastitis were associated with a higher rate of I&D (41/51; 80.4% vs 35/ 76; 46.1%; P ⬍ .001). All the ORSA isolates were susceptible to vancomycin, teicoplanin, linezolid, fusidic acid, and 1 isolate of ORSA was resistant to trimethoprim/sulfamethoxazole (TMP/ SMZ). Among patients with ORSA mastitis, there were only 5 cases that had appropriate antimicrobial agents use at admission. Symptoms in 4 patients subsided under appropriate antimicrobial treatment without I&D. The second most common pathogen isolated was CNS, which was the monomicrobial pathogen isolated from 13 332.e3
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TABLE 2
Comparison of clinical characteristics between patients with and without I&D Characteristics
No I&D (nⴝ47) 29.12 ⫾ 4.35
Age, y
I&D (nⴝ76) 29.30 ⫾ 4.69
P value .833
..............................................................................................................................................................................................................................................
Parity (121 cases)
.....................................................................................................................................................................................................................................
Primipara
29 (61.7%)
Multipara
16 (34.1%)
41 (54.0%)
.274
.....................................................................................................................................................................................................................................
35 (46.0%)
..............................................................................................................................................................................................................................................
Duration of symptoms, d
2.90 ⫾ 2.48
16.83 ⫾ 22.73
⬍ .001
Highest temperature, C
39.04 ⫾ 0.68
37.68 ⫾ 0.84
⬍ .001
Postpartum period, d
44.56 ⫾ 62.57
76.90 ⫾ 82.41
.............................................................................................................................................................................................................................................. o .............................................................................................................................................................................................................................................. a
.037
..............................................................................................................................................................................................................................................
Delivery method (79 cases)
.625
.....................................................................................................................................................................................................................................
Cesarean section
14 (32.6%)
9 (25%)
Vaginal delivery
29 (67.5%)
27 (75%)
..................................................................................................................................................................................................................................... ..............................................................................................................................................................................................................................................
Feeding methods (94 cases)
.....................................................................................................................................................................................................................................
Direct feeding
16 (48.5%)
43 (70.1%)
Pumping then bottle feeding
7 (21.2%)
7 (11.5%)
Combined
9 (27.3%)
10 (16.4%)
Weaning
1 (3.0%)
1 (1.6%)
Discontinued breastfeeding
17 (60.3%)
76 (100%)
⬍ .001
Intrapartum treatment with antimicrobials
19 (40.4%)
14 (18.4%)
.862
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
Laboratory data
..................................................................................................................................................................................................................................... 3
Leukocyte count (10 /L)
13.07 ⫾ 24.65
12.00 ⫾ 4.98
.249
7.75 ⫾ 9.42
3.35 ⫾ 5.76
.008
71.70 ⫾ 18.39
70.95 ⫾ 13.94
.817
C-reactive protein, g/mL
69.38 ⫾ 60.03
59.28 ⫾ 53.69
.413
Hemoglobin, g/dL
14.86 ⫾ 17.75
11.85 ⫾ 1.19
.315
269.60 ⫾ 89.18
316.29 ⫾ 114.02
.032
............................................................................................................................................................................................................................
Bands, %
............................................................................................................................................................................................................................
Segments, %
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... 3
Platelet count (10 /L)
..............................................................................................................................................................................................................................................
Staphylococcus aureus
19 (40.4%)
61 (80.3%)
⬍ .001
Oxacillin-resistant S aureus
10 (21.3%)
42 (55.3%)
⬍ .001
Effective antimicrobials before admission
15 (31.9%)
22 (29.0%)
.161
Effective antimicrobials after admission
23 (48.9%)
.............................................................................................................................................................................................................................................. ..............................................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
44 (57.9%)
.444
..............................................................................................................................................................................................................................................
Duration of hospitalization, d
4.57 ⫾ 1.90
9.94 ⫾ 6.11
⬍ .001
..............................................................................................................................................................................................................................................
I&D, incision and drainage. a
Four patients who received aspiration only are not included in this table.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
patients. Twelve (92.3%) monomicrobial CNS isolates were resistant to oxacillin. Among all 38 CNS isolates, 15 (39.5%) isolates were susceptible to oxacillin. The Figure shows secular trends of puerperal mastitis caused by staphylococci during the study period.
American Journal of Obstetrics & Gynecology OCTOBER 2010
C OMMENT Since 2000, the “baby friendly hospital initiate policy” has been promoted and the prevalence of breastfeeding immediately postpartum and 6 months postpartum among new mothers has increased. In Taiwan, the prevalence of exclusive
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TABLE 3
Microorganisms isolated from 108 patients with positive cultures of bacteria Specimens Microorganisms
Total cases
Monomicrobial (cases)
71
Abscess/ drainage
Blood
9
61
1
Milk
.....................................................................................................................................................................................................................................
Staphylococcus aureus (isolates)
56
7
49
Oxacillin-resistant
37
5
32
Oxacillin-susceptible
19
2
17
13
2
10
1
Oxacillin-resistant
12
1
10
1
Oxacillin-susceptible
1
1
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
CNS
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
Citrobacter koseri
1
1
1
1
...........................................................................................................................................................................................................................
Anaerobic Gram-positive bacilli
..............................................................................................................................................................................................................................................
Polymicrobial (cases)
37
25
12
24
15
9
Oxacillin-resistant
15
10
5
Oxacillin-susceptible
10
6
4
..................................................................................................................................................................................................................................... a
S aureus (isolates)
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
.....................................................................................................................................................................................................................................
CNS
25
19
6
Oxacillin-resistant
11
9
2
Oxacillin-susceptible
14
14
8
8
Viridans streptococcus
2
2
S pneumoniae
1
1
Enterococcus
3
2
Propionibacterium
1
Klebsiella pneumoniae
3
K oxytoca
1
Serratia marcescens
1
1
Acinetobacter junii
1
1
A baumannii
1
1
C koseri
1
1
Gram-positive bacilli
3
3
Bacillus spp
2
2
........................................................................................................................................................................................................................... ...........................................................................................................................................................................................................................
..............................................................................................................................................................................................................................................
Group B Streptococcus
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .....................................................................................................................................................................................................................................
1
.....................................................................................................................................................................................................................................
1
.....................................................................................................................................................................................................................................
3
.....................................................................................................................................................................................................................................
1
..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... ..................................................................................................................................................................................................................................... .............................................................................................................................................................................................................................................. a
One case had mixed growth of both oxacillin-susceptible and -resistant stains of S aureus.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
breastfeeding in the first postpartum month increased from 5.4% in 1989 to 22.3% in 2004,10 or from 33.2% in 2004 to 54.3% in 2008, according to the official report by the Taiwan Bureau of Health Promotion.11 The possible adverse effect of increased breastfeeding is the increased rate of puerperal mastitis.12 Not surprisingly, the incidence of
mastitis requiring inpatient therapy increased in parallel with the prevalence of breastfeeding in our study. The bacteria cultured from milk and/or pus were mainly staphylococci. Of note, ORSA has emerged as a main pathogen. Several cases of puerperal mastitis caused by ORSA among young and healthy women without traditional
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risk factors have been reported in the past few years.13-15 In a study involving patients with puerperal mastitis requiring hospitalization, 59% of cultures from cases with breast abscesses were shown to be ORSA,8 which is compatible with our study. Because of cross-resistance, ORSA is often resistant to all -lactam agents, even in combination with a -lactamase inhibitor.16 Fortunately, community-acquired ORSA strains are usually susceptible to the oral non--lactam agents, such as TMP/SMZ and fusidic acid. Oxacillin resistance has emerged not only in S aureus. In the current study, ⬎90% of monomicrobial CNS isolates were also resistant to oxacillin. There is evidence of horizontal transfer of the methicillin-resistance island of the staphylococcal cassettes chromosome (SCCmec) between staphylococcal species,17 which implies that CNS may serve as an environmental reservoir for the spread of resistance genes encoded in SCCmec to S aureus. Patients undergoing I&D for abscess drainage were associated with more symptomatic days and hospitalization, a higher rate of discontinued breastfeeding, a higher rate of isolation of S aureus and ORSA, and a higher platelet count. Reactive thrombocytosis can occur in patients with severe infections and is associated with abscess formation.18 Thrombocytosis may result from elevated levels of endogenous thrombopoietin, interleukin-6 or other cytokines, and catecholamines that are produced in inflammatory, infectious, or neoplastic conditions or in situations of stress.19 A longer duration of symptoms and hospitalization may be related to the increasing severity associated with abscess formation, and more complicated postsurgery care after I&D. S aureus infection is associated with abscess formation.20,21 The pyogenic property of S aureus is not changed in ORSA.21,22 Therefore, our study also showed that patients caused by ORSA mastitis were associated with a higher rate of I&D in comparison with those caused by non-ORSA mastitis. The incidence of mastitis was highest in the first few weeks postpartum and 73.2% of parturients discontinued
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FIGURE
Secular trends of puerperal mastitis caused by staphylococci during 2000-2008 OSSA
CNS
Incidence 3.00%
25
2.50%
20
2.00%
15
1.50%
10
1.00%
5
0.50%
0
Incidence
case number
ORSA 30
0.00%
2000
2001
2002
2003
2004
2005
2006
2007
2008
Incidence: annual number of hospitalized cases of puerperal mastitis divided by number of deliveries per year at the study hospital. CNS, coagulase-negative staphylococci; ORSA, oxacillin-resistant Staphylococcus aureus; OSSA, oxacillin-susceptible Staphylococcus aureus.
der inappropriate antimicrobial therapy, our study showed only 1 case with appropriate anti-ORSA therapy required I&D eventually. To elucidate the impact of appropriate antimicrobial treatment on ORSA mastitis needs further study. In addition, molecular typing, which could have possibly provided more information about the isolates, was not performed. In conclusion, cases of mastitis increased with the prevalence of breastfeeding in the recent 9 years. Abscess formation may necessitate surgical intervention, but leads to early weaning from breastfeeding and longer hospital stays. For a local liquefied abscess, ultrasoundguided aspiration along with adequate antimicrobial treatment is the preferred option. Oxacillin resistance has emerged in the Gram-positive cocci isolated from milk and abscesses. Empiric antimicrobial therapy to cover oxacillin-resistant staphylococci is needed among patients who fail to respond to -lactam f agents.
Lee. Puerperal mastitis requiring hospitalization. Am J Obstet Gynecol 2010.
REFERENCES
breastfeeding. Once patients had an I&D and began regular wet dressings, the morbidity and subsequent hospitalization often led to discontinuation of breastfeeding, even though there is consensus that lactation should be continued.2 In the current study, all 76 cases undergoing I&D discontinued breastfeeding, whereas the 4 cases who had an aspiration of abscess continued breastfeeding (100% vs 0%; P ⬍ .001). Although not proven, it appears that an invasive intervention of a breast abscess decreases the rate of breastfeeding. In addition to the wound pain, patients might choose to discontinue breastfeeding because of a disconnection with their infants, fear of residual medication in milk, the potential hazard of bacteria-containing milk to infants, or following the recommendations of health care givers. Nevertheless, prior studies have shown that there are no complications associated with continued breastfeeding, even in the presence of a breast abscess.23,24 Although there has been a case report of staphylococcal scalded skin syndrome in 332.e5
a breastfed infant whose mother had mastitis or a breast abscess, the infant may have been infected via close contact rather than breastfeeding alone.25 There were several limitations to the current study. First, because of the study’s retrospective nature, clinical data in the medical records may have been incomplete. Second, our findings are not generalizable to all patients with puerperal mastitis because empirically treated mastitis might be cured without collecting a culture or hospitalization, thereby overestimating the burden of disease. Resistant pathogens tend to survive among patients who responded poorly to empiric antimicrobial therapy. Perhaps in Taiwan, the clinicians are used to prescribing empiric antimicrobials, which do not cover ORSA, for example, -lactam agents for patients with mastitis, we found only 5 cases with ORSA mastitis had appropriate antimicrobial agents use at admission. Although previous study reported that no treatment failure among 15 of 16 women with culture-proven ORSA mastitis un-
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