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Isolation of methicillin resistant Staphylococcus aureus from the surface and core of tonsils in children
International Journal of Pediatric Otorhinolaryngology (2006) 70, 2099—2102
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Isolation of methicillin resistant Staphylococcus aureus from the surface and core of tonsils in children Itzhak Brook a,*, Perry A. Foote b a b
Departments of Pediatrics, Georgetown University School of Medicine, Washington, DC, USA Department of Otorhinolaryngology, University of Florida, Alachua General Hospital, Gainesville, FL, USA
Received 26 May 2006; accepted 9 August 2006
KEYWORDS Methicillin resistant; Staphylococcus aureus; Beta-lactamase; Tonsils
Summary Background: The rate of recovery methicillin resistant Staphylococcus aureus (MRSA) in tonsils that were removed because of recurrent Group A-b-hemolytic streptococci (GABHS) tonsillitis was not previously reported. MRSA may serve as a potential source for the spread of these organisms to other body sites as well to other individuals. This study investigated the rate of recovery of MRSA as well as other aerobic organisms from tonsils that were removed because of recurrent GABHS infection. Patients and methods: Core and surface tonsillar cultures for aerobic bacteria were obtained from 44 children who had tonsillectomy because of recurrent GABHS tonsillitis. Results: A total of 167 aerobic isolates were recovered from the core of the tonsils (3.8/ specimen) and 151 (3.4/specimen) were isolated from the surface. The predominant isolates were alpha-hemolytic streptococci, GABHS, S. aureus, gamma-hemolytic streptococci, Haemophilus influenzae and Moraxella catarrhalis. Concordence in the recovery of all organisms was noted in 117 instances. Certain organisms (i.e. GABHS, S. aureus) were recovered more often from the tonsillar cores, where other (i.e. alpha-hemolytic streptococci, gamma-hemolytic streptococci) were recovered more often from the tonsillar surface. Forty-four beta-lactamase-producing bacteria (BLPB) were recovered from 32 (75%) of the tonsillar cores, and 28 were isolated from 23 (52%) of the tonsillar surfaces. The predominant BLPB were S. aureus, H. influenzae and M. catarrhalis. Seven isolates of MRSA were recovered from the cores and two were isolated from the surface. Five of the core isolates and the two surface isolates were also BLPB. All of the MRSA isolates were resistant to oxacillin, penicillin and erythromycin and were susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin.
* Correspondence to: 4431 Albemarle St. NW, Washington, DC 20016, USA. Tel.: +1 301 295 2698; fax: +1 202 244 6809. E-mail address: [email protected] (I. Brook). 0165-5876/$ — see front matter. Crown Copyright # 2006 Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2006.08.004
2100
I. Brook, P.A. Foote Conclusions: These data demonstrated that in recurrently GABHS infected tonsils, BLPB was recovered from over 75% of the tonsillar cores, core tonsillar cultures yielded more GABHS and S. aureus, and MRSA was isolated from 16% of the tonsils. Crown Copyright # 2006 Published by Elsevier Ireland Ltd. All rights reserved.
1. Introduction The failure of penicillin to eradicate Group A-bhemolytic streptococci (GABHS) from inflamed tonsils is of great concern [1]. Various theories have been offered to explain this phenomenon. One is that beta-lactamase-producing bacteria (BLPB) protects GABHS by inactivating penicillin [2]. In previous studies, BLPB were recovered from over three fourth of the cores of tonsils of patients, who had tonsillectomy for recurrent infection [2]. The most predominant aerobic BLPB recovered in about half of these tonsils was Stapylococcus aureus. An increase in the recovery of methicillin resistant S. aureus (MRSA) was recently noted in various infectious sites as well as the nasal mucosa of normal individuals [3]. However, the rate of recovery of these organisms in tonsils that were removed because of recurrent GABHS was not previously reported. The presence of MRSA in the core of the tonsils may serve as a potential source for the spread of these organisms to other body sites as well as an origin for dissemination to other individuals. Furthermore, MRSA that also produces beta-lactamase can survive treatment with beta-lactam antibiotics and continue to protect GABHS from penicillins. This study investigated the rate of recovery of MRSA as well as other aerobic organisms from tonsils that were removed because of recurrent GABHS infection.
2. Patients and methods 2.1. Patients Forty-four patients (25 males), consecutively scheduled for elective tonsillectomy because of recurrent GABHS tonsillitis, participated in this study. Their mean age was 7 years, 11 months (range 4—15 years). Criteria for inclusion were: a history of recurrent GABHS pharyngotonsillitis (at least six episodes within the preceding 2 years, at least four caused by GABHS); and age at least 4 years. The study was performed between June 1998 and June 2003 and was approved by the IRB. Excluded were subjects who received antimicrobials or had any infection during the previous month. Prior to surgery all had a general
physical and otolaryngologic examinations, a complete blood cell count, and urinalysis.
2.2. Microbiology Following a tonsillectomy, the tonsils were placed in a sterile container and promptly taken to the microbiology laboratory. The surface of one of the tonsils was rubbed thoroughly with a sterile cotton applicator. One side of that tonsil was cauterized with a heated scalpel, and an incision was made through the area, cutting the tonsil in half. The core of the tonsil was swabbed with a sterile cotton-tipped applicator, and both swabs were placed onto aerobic and anaerobic transport media (Port-A-Cul, BBL, Becton Dickinson Co., Cockeysville, MD). The specimens were transported to the bacteriology laboratory and inoculated within 24 h of collection. Sheep’s blood (5%), chocolate and MacConkey agar plates were inoculated for the isolation of aerobic organisms. The culture plates were incubated aerobically at 37 8C (MacConkey agar) and under 5% carbon dioxide (blood and chocolate agars), and they were examined at 24 and 48 h [4]. Beta-lactamase activity was determined on five colonies of each morphologic feature of all isolates by using the cefinaz disk (BBL, Cockeysville, MD). S. aureus isolates were screened for oxacillin resistance using the Clinical Laboratory Standard Institute disk diffusion method [5]. Overnight cultures from blood agar plate were suspended in Mueller-Hinton broth to the turbidity of 0.5 McFarland and plated on Mueller-Hinton agar, and a 1 mg oxacillin disc was placed with the inoculum. Zone diameters were measured and recorded after a 24 h incubation at 35 8C (susceptible, equal or less than 13 mm; intermediate between 11 and 12 mm; and resistant equal or less than 10 mm). The susceptibilities of the MRSA isolates to oxacillin, penicillin, erythromycin, clindamycin, trimethoprim-sulfamethoxazole and vancomycin were determined by the Clinical Laboratory Standard Institute disk diffusion method [5].
3. Results One hundred sixty seven aerobic isolates were recovered from the core of the tonsils (3.8 per
Methicillin resistant Staphylococcus aureus in tonsils
2101
Table 1 Aerobic organisms isolated from excised tonsils from 44 children Organisms
Number of isolates in the tonsillar core
Number of isolates in the tonsillar surface
Concordance in recovery of organisms between core and surface
Gram-positive Streptococcus pneumoniae Alpha-hemolytic Streptococcus Gamma-hemolytic Streptococcus
3 35 24
2 40 35
2 30 19
Beta-hemolytic Streptococcus Group A Group C Group F
27 3 3
19 1 2
16 1 2
19 (19)
14 (14)
13 (11)
2 5 (5)
0 2 (2)
0 2 (2)
3
3 (2)
3 (2)
12 (8) 5
8 (4) 6
7 (4) 4
3 (1) 18 (9)
1 13 (4)
3 (2) 2
2 (2) 3
2 (2) 2
167 (44)
151 (28)
117 (21)
Staphylococcus aureus (beta-lactamase producing) Staphylococcus aureus (MRSA) Staphylococcus aureus (beta-lactamase producing and MRSA) Staphylococcus epidermidis Gram-negative Moraxella catarrhalis Diphtheroid species Haemophilus influenzae Type b Non-type b Haemophilus parainfluenzae Eikenella corrodens Total
1 13
In parenthesis number of BLPB.
specimen) (Table 1). The predominant isolates were alpha-hemolytic streptococci (35 isolates), GABHS (27), S. aureus (26), gamma-hemolytic streptococci (24), Haemophilus influenzae (21) and Moraxella catarrhalis (12). One hundred fifty one aerobic isolates were recovered from the surface of the tonsils (3.4 per specimen)(Table 1). The predominate isolates were alpha-hemolytic streptococci (40 isolates), gamma-hemolytic streptococci (35), GABHS (19), S. aureus (16), H. influenzae (14) and M. catarrhalis (8). No consistent pattern of combinations of different organisms was noted in either core or surface sites. Concordence in the recovery of all organisms was noted in 117 instances. A comparison between the core and surface specimens showed that in many instances, organisms that were recovered in the core cultures were also isolated from the surface cultures (Table 1). Certain organisms (i.e. GABHS, S. aureus) were recovered more often from the tonsilar cores, where other (i.e. alpha-hemolytic streptococci, gamma-hemolytic streptococci) were recovered more often from the tonsilar surface. Forty four BLPB were recovered from 33 (75%) of the tonsillar cores, and 28 were isolated from 23
(52%) of the tonsillar surfaces. Concordence in the recovery of BLPB was noted in 21 instances. The predominant BLPB were S. aureus, H. influenzae and M. catarrhalis. Seven isolates of MRSA were recovered from the cores and two were isolated from the surfaces in concordant individuals. Five of the core isolates and the two surface isolates were also BLPB. All of the MRSA isolates were resistant to oxacillin, penicillin and erythromycin and were susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin.
4. Discussion This study demonstrated for the first time the recovery of MRSA from 16% of the tonsils removed because of recurrent GABHS tonsillitis. Although we have been culturing tonsils removed because of recurrent GABHS tonsillitis for 30 years, [6] we have never isolated MRSA from these tonsils until recently. Most of these MRSA (5 of 7) were isolated from core of the tonsils and would have been missed on routine cultures of the surface of the tonsils.
2102 Our data confirms previous studies that demonstrated the recovery of BLPB from over 75% of the cores of tonsils of patients, who had tonsillectomy for recurrent infection [2]. One explanation for the failure of penicillin to eradicate GABHS tonsillitis is that repeated administration of penicillin may select BLPB that can protect not only themselves from penicillin but also penicillin-susceptible pathogens [2]. The recovery of aerobic and anaerobic BLPB in more than three fourths of the patients with recurrent GABHS tonsillitis, [2,6] the ability to measure beta-lactamase activity in the core of the tonsils, [7] and the response of patient with recurrent GABHS tonsillitis to antimicrobial agents effective against BLPB [2,6,8,9] support this explanation. The emergence of MRSA in the tonsillar flora in children with recurrent GABHS tonsillitis may contribute to the difficulty in eradicating GABHS with penicillins and other antimicrobials that are ineffective against this organism. MRSA are generally resistant to beta-lactam antimicrobials and generally susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin. Since most of the MRSA (5 of 7) were also betalactamase producers their presence could potentially interfere with the eradication of GABHS by penicillin [2]. MRSA that is also able to produce beta-lactamase can survive treatment with beta-lactam antibiotics and continue to ‘‘shield’’ GABHS from penicillins through the production of the enzyme beta-lactamase. Most of the S. aureus isolated from the tonsilar cores of our patients (19 of 26 or 73%) were, however, beta-lactamase producers and not MRSA. These organisms are susceptible to beta-lactamase resistant penicillins as well as most cephalosporins. This study also confirms the discrepancies between the surface and core microflora of tonsils [10,11]. Core tonsillar cultures yielded more GABHS and S. aureus including MRSA as well as anaerobic bacteria. Furthermore, however, in contrast to our previous studies, we did not employ methods for the recovery of anaerobic bacteria in this study [2,10].
I. Brook, P.A. Foote This study demonstrated the isolation of MRSA mostly from the cores recurrently inflamed tonsils. Further studies are warranted to evaluate the efficacy of therapies effective against these organisms in the eradication of acute and recurrent GABHS tonsillitis.
References [1] E.L. Kaplan, D.R. Johnson, Unexplained reduced microbiological efficacy of intramuscular benzathine penicillin G and of oral penicillin V in eradication of group a streptococci from children with acute pharyngitis, Pediatrics 108 (2001) 1180—1186. [2] I. Brook, The role of beta-lactamase producing bacteria and bacterial interference in streptococcal tonsillitis, Int. J. Antimicrob. Agents 17 (2001) 439—442. [3] M.J. Kuehnert, D. Kruszon-Moran, H.A. Hill, G. McQuillan, S.K. McAllister, G. Fosheim, L.K. McDougal, J. Chaitram, B. Jensen, S.K. Fridkin, G. Killgore, F.C. Tenover, Prevalence of Staphylococcus aureus Nasal Colonization in the United States, 2001—2002, J. Infect. Dis. 15 (193) (2006) 172—179. [4] P.R. Murray, E.J. Barron, J.H. Jorenson, et al., Manual of Clinical Microbiology, eight ed., ASM Press, Washington, DC, 2003. [5] NCCL, Methods for Disc Diffusion: Approve Standard M2-8: Performance Standard for Antimicrobial Disc Susceptibility Tests, NCCLS, Wayne, PA, 2003. [6] I. Brook, P. Yocum, P.A. Foote Jr., Changes in the core tonsillar bacteriology of recurrent tonsillitis, 1977—1993, Clin. Infect. Dis. 21 (1995) 171—176. [7] I. Brook, P. Yocum, Quantitative measurement of beta-lactamase in tonsils of children with recurrent tonsillitis, Acta Otolaryngol. (Stockh.) 98 (1984) 556—559. [8] J.R. Casey, M.E. Pichichero, Meta-analysis of cephalosporin versus penicillin treatment of group A streptococcal tonsillopharyngitis in children, Pediatrics 113 (2004) 866—882. [9] P.A. Foote Jr., I. Brook, Penicillin and clindamycin therapy in recurrent tonsillitis. Effect of microbial flora, Arch. Otolaryngol. Head Neck Surg. 115 (1989) 856—859. [10] I. Brook, P. Yocum, K. Shah, Surface vs. core-tonsillar aerobic and anaerobic flora in recurrent tonsillitis, JAMA 244 (1980) 1696—1698. [11] I.J. Mitchelmore, P.G. Reilly, A.J. Hay, S. Tabaqchali, Tonsil surface and core cultures in recurrent tonsillitis: prevalence of anaerobes and beta-lactamase producing organisms, Eur. J. Clin. Microbiol. Infect. Dis. 13 (1994) 542—548.
www.elsevier.com/locate/ijporl
Isolation of methicillin resistant Staphylococcus aureus from the surface and core of tonsils in children Itzhak Brook a,*, Perry A. Foote b a b
Departments of Pediatrics, Georgetown University School of Medicine, Washington, DC, USA Department of Otorhinolaryngology, University of Florida, Alachua General Hospital, Gainesville, FL, USA
Received 26 May 2006; accepted 9 August 2006
KEYWORDS Methicillin resistant; Staphylococcus aureus; Beta-lactamase; Tonsils
Summary Background: The rate of recovery methicillin resistant Staphylococcus aureus (MRSA) in tonsils that were removed because of recurrent Group A-b-hemolytic streptococci (GABHS) tonsillitis was not previously reported. MRSA may serve as a potential source for the spread of these organisms to other body sites as well to other individuals. This study investigated the rate of recovery of MRSA as well as other aerobic organisms from tonsils that were removed because of recurrent GABHS infection. Patients and methods: Core and surface tonsillar cultures for aerobic bacteria were obtained from 44 children who had tonsillectomy because of recurrent GABHS tonsillitis. Results: A total of 167 aerobic isolates were recovered from the core of the tonsils (3.8/ specimen) and 151 (3.4/specimen) were isolated from the surface. The predominant isolates were alpha-hemolytic streptococci, GABHS, S. aureus, gamma-hemolytic streptococci, Haemophilus influenzae and Moraxella catarrhalis. Concordence in the recovery of all organisms was noted in 117 instances. Certain organisms (i.e. GABHS, S. aureus) were recovered more often from the tonsillar cores, where other (i.e. alpha-hemolytic streptococci, gamma-hemolytic streptococci) were recovered more often from the tonsillar surface. Forty-four beta-lactamase-producing bacteria (BLPB) were recovered from 32 (75%) of the tonsillar cores, and 28 were isolated from 23 (52%) of the tonsillar surfaces. The predominant BLPB were S. aureus, H. influenzae and M. catarrhalis. Seven isolates of MRSA were recovered from the cores and two were isolated from the surface. Five of the core isolates and the two surface isolates were also BLPB. All of the MRSA isolates were resistant to oxacillin, penicillin and erythromycin and were susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin.
* Correspondence to: 4431 Albemarle St. NW, Washington, DC 20016, USA. Tel.: +1 301 295 2698; fax: +1 202 244 6809. E-mail address: [email protected] (I. Brook). 0165-5876/$ — see front matter. Crown Copyright # 2006 Published by Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2006.08.004
2100
I. Brook, P.A. Foote Conclusions: These data demonstrated that in recurrently GABHS infected tonsils, BLPB was recovered from over 75% of the tonsillar cores, core tonsillar cultures yielded more GABHS and S. aureus, and MRSA was isolated from 16% of the tonsils. Crown Copyright # 2006 Published by Elsevier Ireland Ltd. All rights reserved.
1. Introduction The failure of penicillin to eradicate Group A-bhemolytic streptococci (GABHS) from inflamed tonsils is of great concern [1]. Various theories have been offered to explain this phenomenon. One is that beta-lactamase-producing bacteria (BLPB) protects GABHS by inactivating penicillin [2]. In previous studies, BLPB were recovered from over three fourth of the cores of tonsils of patients, who had tonsillectomy for recurrent infection [2]. The most predominant aerobic BLPB recovered in about half of these tonsils was Stapylococcus aureus. An increase in the recovery of methicillin resistant S. aureus (MRSA) was recently noted in various infectious sites as well as the nasal mucosa of normal individuals [3]. However, the rate of recovery of these organisms in tonsils that were removed because of recurrent GABHS was not previously reported. The presence of MRSA in the core of the tonsils may serve as a potential source for the spread of these organisms to other body sites as well as an origin for dissemination to other individuals. Furthermore, MRSA that also produces beta-lactamase can survive treatment with beta-lactam antibiotics and continue to protect GABHS from penicillins. This study investigated the rate of recovery of MRSA as well as other aerobic organisms from tonsils that were removed because of recurrent GABHS infection.
2. Patients and methods 2.1. Patients Forty-four patients (25 males), consecutively scheduled for elective tonsillectomy because of recurrent GABHS tonsillitis, participated in this study. Their mean age was 7 years, 11 months (range 4—15 years). Criteria for inclusion were: a history of recurrent GABHS pharyngotonsillitis (at least six episodes within the preceding 2 years, at least four caused by GABHS); and age at least 4 years. The study was performed between June 1998 and June 2003 and was approved by the IRB. Excluded were subjects who received antimicrobials or had any infection during the previous month. Prior to surgery all had a general
physical and otolaryngologic examinations, a complete blood cell count, and urinalysis.
2.2. Microbiology Following a tonsillectomy, the tonsils were placed in a sterile container and promptly taken to the microbiology laboratory. The surface of one of the tonsils was rubbed thoroughly with a sterile cotton applicator. One side of that tonsil was cauterized with a heated scalpel, and an incision was made through the area, cutting the tonsil in half. The core of the tonsil was swabbed with a sterile cotton-tipped applicator, and both swabs were placed onto aerobic and anaerobic transport media (Port-A-Cul, BBL, Becton Dickinson Co., Cockeysville, MD). The specimens were transported to the bacteriology laboratory and inoculated within 24 h of collection. Sheep’s blood (5%), chocolate and MacConkey agar plates were inoculated for the isolation of aerobic organisms. The culture plates were incubated aerobically at 37 8C (MacConkey agar) and under 5% carbon dioxide (blood and chocolate agars), and they were examined at 24 and 48 h [4]. Beta-lactamase activity was determined on five colonies of each morphologic feature of all isolates by using the cefinaz disk (BBL, Cockeysville, MD). S. aureus isolates were screened for oxacillin resistance using the Clinical Laboratory Standard Institute disk diffusion method [5]. Overnight cultures from blood agar plate were suspended in Mueller-Hinton broth to the turbidity of 0.5 McFarland and plated on Mueller-Hinton agar, and a 1 mg oxacillin disc was placed with the inoculum. Zone diameters were measured and recorded after a 24 h incubation at 35 8C (susceptible, equal or less than 13 mm; intermediate between 11 and 12 mm; and resistant equal or less than 10 mm). The susceptibilities of the MRSA isolates to oxacillin, penicillin, erythromycin, clindamycin, trimethoprim-sulfamethoxazole and vancomycin were determined by the Clinical Laboratory Standard Institute disk diffusion method [5].
3. Results One hundred sixty seven aerobic isolates were recovered from the core of the tonsils (3.8 per
Methicillin resistant Staphylococcus aureus in tonsils
2101
Table 1 Aerobic organisms isolated from excised tonsils from 44 children Organisms
Number of isolates in the tonsillar core
Number of isolates in the tonsillar surface
Concordance in recovery of organisms between core and surface
Gram-positive Streptococcus pneumoniae Alpha-hemolytic Streptococcus Gamma-hemolytic Streptococcus
3 35 24
2 40 35
2 30 19
Beta-hemolytic Streptococcus Group A Group C Group F
27 3 3
19 1 2
16 1 2
19 (19)
14 (14)
13 (11)
2 5 (5)
0 2 (2)
0 2 (2)
3
3 (2)
3 (2)
12 (8) 5
8 (4) 6
7 (4) 4
3 (1) 18 (9)
1 13 (4)
3 (2) 2
2 (2) 3
2 (2) 2
167 (44)
151 (28)
117 (21)
Staphylococcus aureus (beta-lactamase producing) Staphylococcus aureus (MRSA) Staphylococcus aureus (beta-lactamase producing and MRSA) Staphylococcus epidermidis Gram-negative Moraxella catarrhalis Diphtheroid species Haemophilus influenzae Type b Non-type b Haemophilus parainfluenzae Eikenella corrodens Total
1 13
In parenthesis number of BLPB.
specimen) (Table 1). The predominant isolates were alpha-hemolytic streptococci (35 isolates), GABHS (27), S. aureus (26), gamma-hemolytic streptococci (24), Haemophilus influenzae (21) and Moraxella catarrhalis (12). One hundred fifty one aerobic isolates were recovered from the surface of the tonsils (3.4 per specimen)(Table 1). The predominate isolates were alpha-hemolytic streptococci (40 isolates), gamma-hemolytic streptococci (35), GABHS (19), S. aureus (16), H. influenzae (14) and M. catarrhalis (8). No consistent pattern of combinations of different organisms was noted in either core or surface sites. Concordence in the recovery of all organisms was noted in 117 instances. A comparison between the core and surface specimens showed that in many instances, organisms that were recovered in the core cultures were also isolated from the surface cultures (Table 1). Certain organisms (i.e. GABHS, S. aureus) were recovered more often from the tonsilar cores, where other (i.e. alpha-hemolytic streptococci, gamma-hemolytic streptococci) were recovered more often from the tonsilar surface. Forty four BLPB were recovered from 33 (75%) of the tonsillar cores, and 28 were isolated from 23
(52%) of the tonsillar surfaces. Concordence in the recovery of BLPB was noted in 21 instances. The predominant BLPB were S. aureus, H. influenzae and M. catarrhalis. Seven isolates of MRSA were recovered from the cores and two were isolated from the surfaces in concordant individuals. Five of the core isolates and the two surface isolates were also BLPB. All of the MRSA isolates were resistant to oxacillin, penicillin and erythromycin and were susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin.
4. Discussion This study demonstrated for the first time the recovery of MRSA from 16% of the tonsils removed because of recurrent GABHS tonsillitis. Although we have been culturing tonsils removed because of recurrent GABHS tonsillitis for 30 years, [6] we have never isolated MRSA from these tonsils until recently. Most of these MRSA (5 of 7) were isolated from core of the tonsils and would have been missed on routine cultures of the surface of the tonsils.
2102 Our data confirms previous studies that demonstrated the recovery of BLPB from over 75% of the cores of tonsils of patients, who had tonsillectomy for recurrent infection [2]. One explanation for the failure of penicillin to eradicate GABHS tonsillitis is that repeated administration of penicillin may select BLPB that can protect not only themselves from penicillin but also penicillin-susceptible pathogens [2]. The recovery of aerobic and anaerobic BLPB in more than three fourths of the patients with recurrent GABHS tonsillitis, [2,6] the ability to measure beta-lactamase activity in the core of the tonsils, [7] and the response of patient with recurrent GABHS tonsillitis to antimicrobial agents effective against BLPB [2,6,8,9] support this explanation. The emergence of MRSA in the tonsillar flora in children with recurrent GABHS tonsillitis may contribute to the difficulty in eradicating GABHS with penicillins and other antimicrobials that are ineffective against this organism. MRSA are generally resistant to beta-lactam antimicrobials and generally susceptible to clindamycin, trimethoprim-sulfamethoxazole and vancomycin. Since most of the MRSA (5 of 7) were also betalactamase producers their presence could potentially interfere with the eradication of GABHS by penicillin [2]. MRSA that is also able to produce beta-lactamase can survive treatment with beta-lactam antibiotics and continue to ‘‘shield’’ GABHS from penicillins through the production of the enzyme beta-lactamase. Most of the S. aureus isolated from the tonsilar cores of our patients (19 of 26 or 73%) were, however, beta-lactamase producers and not MRSA. These organisms are susceptible to beta-lactamase resistant penicillins as well as most cephalosporins. This study also confirms the discrepancies between the surface and core microflora of tonsils [10,11]. Core tonsillar cultures yielded more GABHS and S. aureus including MRSA as well as anaerobic bacteria. Furthermore, however, in contrast to our previous studies, we did not employ methods for the recovery of anaerobic bacteria in this study [2,10].
I. Brook, P.A. Foote This study demonstrated the isolation of MRSA mostly from the cores recurrently inflamed tonsils. Further studies are warranted to evaluate the efficacy of therapies effective against these organisms in the eradication of acute and recurrent GABHS tonsillitis.
References [1] E.L. Kaplan, D.R. Johnson, Unexplained reduced microbiological efficacy of intramuscular benzathine penicillin G and of oral penicillin V in eradication of group a streptococci from children with acute pharyngitis, Pediatrics 108 (2001) 1180—1186. [2] I. Brook, The role of beta-lactamase producing bacteria and bacterial interference in streptococcal tonsillitis, Int. J. Antimicrob. Agents 17 (2001) 439—442. [3] M.J. Kuehnert, D. Kruszon-Moran, H.A. Hill, G. McQuillan, S.K. McAllister, G. Fosheim, L.K. McDougal, J. Chaitram, B. Jensen, S.K. Fridkin, G. Killgore, F.C. Tenover, Prevalence of Staphylococcus aureus Nasal Colonization in the United States, 2001—2002, J. Infect. Dis. 15 (193) (2006) 172—179. [4] P.R. Murray, E.J. Barron, J.H. Jorenson, et al., Manual of Clinical Microbiology, eight ed., ASM Press, Washington, DC, 2003. [5] NCCL, Methods for Disc Diffusion: Approve Standard M2-8: Performance Standard for Antimicrobial Disc Susceptibility Tests, NCCLS, Wayne, PA, 2003. [6] I. Brook, P. Yocum, P.A. Foote Jr., Changes in the core tonsillar bacteriology of recurrent tonsillitis, 1977—1993, Clin. Infect. Dis. 21 (1995) 171—176. [7] I. Brook, P. Yocum, Quantitative measurement of beta-lactamase in tonsils of children with recurrent tonsillitis, Acta Otolaryngol. (Stockh.) 98 (1984) 556—559. [8] J.R. Casey, M.E. Pichichero, Meta-analysis of cephalosporin versus penicillin treatment of group A streptococcal tonsillopharyngitis in children, Pediatrics 113 (2004) 866—882. [9] P.A. Foote Jr., I. Brook, Penicillin and clindamycin therapy in recurrent tonsillitis. Effect of microbial flora, Arch. Otolaryngol. Head Neck Surg. 115 (1989) 856—859. [10] I. Brook, P. Yocum, K. Shah, Surface vs. core-tonsillar aerobic and anaerobic flora in recurrent tonsillitis, JAMA 244 (1980) 1696—1698. [11] I.J. Mitchelmore, P.G. Reilly, A.J. Hay, S. Tabaqchali, Tonsil surface and core cultures in recurrent tonsillitis: prevalence of anaerobes and beta-lactamase producing organisms, Eur. J. Clin. Microbiol. Infect. Dis. 13 (1994) 542—548.