Perspectives on the bacteriology of postoperative obstetric-gynecologic infections

Perspectives on the bacteriology of postoperative obstetric-gynecologic infections Sebastian Faro, MD, PhD, Lou E. Phillips, PhD, and Mark G. Martens, MD Houston Texas The development of postoperative infections is influenced by both host and external factors. The present report focuses on the influence of prophylactic agents on the apparent cause of infection after cesarean section and vaginal hysterectomy. The correlation between in vitro susceptibility patterns of potential pathogens and normal flora and in vivo response is also considered. (AM J 0BSTET GYNECOL 1988;158:694-700.)

Key words: Endometritis, vaginal cutl cellulitis, prophylaxis

The development of female pelvic infections after obstetric or gynecologic surgery is frequently caused by endogenous microflora of the lower genital tract. During labor or an operative procedure, such as vaginal hysterectomy or cesarean section, these bacteria gain entrance to the upper genital tract and pelvic cavity. An inoculum of significant quantity may colonize tissue pedicles and incised tissue margins. The presence of blood and devascularized tissue is an ideal environment for the growth of these organisms. The lower genital tract is colonized by large numbers of aerobic and anaerobic gram-negative and gram-positive bacteria. Included in this bacterial milieu are streptococci, staphylococci, members of the Enterobacteriaaae, Bactnoides, and other anaerobes. In addition, metabolic by products of commensal bacteria, such as Lactobacillus, diphtheroids, etc., maintain the equilibrium ofthe environment of the lower genital tract and thereby keep the potentially pathogenic bacteria suppressed. In addition to maintaining the pH of the vagina below 4.5 by the production of lactic acid, certain strains of Lartobacillu.1 have been found to produce hydrogen peroxide'" and bacteriocins.' Both substances influence the proliferation of other organisms within the lower genital tract. Although Lactobacillus is commonly isolated from the lower genital tract in healthy patients, preliminary studies suggest that it is absent or reduced in numbers in patients with bacter·ial vaginitis (vaginosis), and these patients appear to be at increased risk for developing postoperative pelvic infection.' Postoperative pelvic infection rates, for example, endometritis after cesarean section and pelvic cellulitis after hysterectomy, vary from institution to institution Frum the Department uf Medicine.

of Ob.1lelrin

and Gynemlogy. Bavlor College

Reprint req1wts: S. Faro, MD, PhD, Department rf OhstetricsGyneco/ogy, Baylor College of Medicine. One Baylor Plaza, Howton, TX 77030.

694

and are dependent on many variables. The development of postpartum endometritis is associated with the duration from rupture of amniotic membranes to surgery, as well as the number of vaginal examinations and the use of invasive fetal and uterine monitoring devices. In the gynecologic patient undergoing hysterectomy, the vaginal versus abdominal route is significant as is the duration of surgery, blood loss, and tissue trauma, as well as inherent patient factors. Contributing patient risk factors include morbid obesity, peripheral vascular disease, chronic debilitating disease, and immunologic compromise. The use of prophylactic antibiotics has been advocated to decrease the risk of postoperative infection. The ideal antibiotic for prophylaxis will lower the number of pathogens, not affect the commensal bacteria, and not select resistant bacteria. The main effect of antibiotic prophylaxis is to decrease the overall number of bacteria present within the lower genital tract. This reduction in numbers of bacteria, that is, inoculum size, allows the host at the time of surgical trauma to inhibit pathogenic bacteria from establishing an infection. However, the use of antibiotics commonly used for prophylaxis appears to influence the flora of the lower genital tract by selecting resistant bacteria. Controversy exists concerning which antibiotic is appropriate, that is, a broad-spectrum penicillin or a first-, second-, or third-generation cephalosporin. The latter have been advocated because of their 13-lactamase resistance. However, few reports have addressed the influence different prophylactic agents may have on the normal vaginal flora and what effect that phenomenon may have on the development of infection. The present report considers the overall recovery of bacteria from infected patients as well as the influence of prophylactic agents on normal vaginal flora and the observed effects on the development of postoperative infection.

Bacteriology of postop ob-gyn infections 695

Volume l3H Number :1. Part :!

Table I. Bacteria isolated from unimicrobial cases of endometritis*; total isolates Aerobic organisms isolated

No. isolated

Streptococcus faecali.\ Staphylvcoccus agalactiae Staphylococcus epidermidis .\Iicroaerophilic streptococci

33 10 8

2

l!scherichia coli Entrrobattn Proteus mirabih1

=

83

Anaerobic organisms isolated Bacteroides Bacteroides bivius Bacteroides fragilis Fusobacterium nucleatum Gaffkya anaerohia

No. isolated

3 3 2 2 l

9 7 3

*Specimens taken from endometrium.

Table II. Microaerophilic and facultative anaerobic organisms isolated from patients with polymicrobial endometritis*; total isolates 262 No. isolated Streptocorcus faecalis Staphylococcus epidermidts Streptowccus agalactiae Staphylococcus aureus Microaerophilic streptococci Diphtheroids Streptocorrus p_vogenes

80

42 25 13 4

2 I

Gram-negative organisms isolated Escherichia coli Klebsiella pneumoniae E nterobacter cloacae Proteus mirabili.1 Citrobacter freundii Enterobacter aerogenes Pseudomonas aerug~nosa Gardnerella vagina/is

No. isolated

42 14 13 10

7 3 3 I

*Specimens taken from endometrium.

Methods

A total of 1783 cesarean sections were reviewed for the incidence of postpartum endometritis. In addition, 543 patients delivered by cesarean section were reviewed for the development of wound infection. Postpartum endometritis was defined by the following criteria: a temperature of> 10 l oF, white blood cell count > 14,000 or > l 0% increase in immature polymorphonuclear leukocytes, sinus tachycardia, and marked uterine tenderness (fundal). Wound infection was defined as the presence of erythema and pus and spontaneous dehiscence or the need for surgical debridement. All infected sites were cultured for aerobic and anaerobic bacteria. Isolates were identified by either the API 20 E or API 20 A strips (Analytab, Plainview, New York), the BBL Sceptor System (Johnston Laboratories. Walkersville, Maryland), or conventional methodology.'' Susceptibility patterns were determined by standard panels or specially prepared research panels furnished by Johnston Laboratories. Most specimens were also cultured for Chlam}dia trachoma/is, Mycoplasma species, and Ureaplasma urealyticum as described previously."· 7 Venous blood was obtained for the culture of aerobic and anaerobic bacteria as well as Mycoplasma species and U. urealyticum in most cases. Ninety-two percent of the patients delivered by cesarean section were given cefazolin prophylaxis, which was administered in a 1 grn intravenous dose immediately after cord-clamping, followed by two l gm doses

8 hours after surgery and 16 hours after surgery. Patients undergoing vaginal hysterectomy were given either cefoxitin (90 patients), piperacillin (45 patients), or mezlocillin (46 patients) for prophylaxis. Cefoxitin was administered in 2 gm doses; the first dose was given 30 minutes before surgery followed by 2 gm doses given 8 and 16 hours after surgery. Piperacillin and mezlocillin were administered in doses of 4 grn and followed a similar schedule. Preoperative and postoperative vaginal specimens for the culture and identification of anaerobic and aerobic bacteria were collected. A pilot study of a small number of patients was conducted to determine the effect of cefazolin, cefoxitin, and cefotetan prophylaxis on normal vaginal flora, specifically Lactobacillus and Streptococcus faecalis. For that purpose five patients undergoing vaginal hysterectomy received three 2 gm doses of cefoxitin and five patients received one 1 gm dose of cefotetan. In addition, five patients undergoing cesarean section received three 1 gm doses of cefazolin, five patients receiverl three 2 gm doses of cefoxitin, and 10 patients received one 1 gm dose of cefotetan. Vaginal cultures were collected before the first dose of antibiotic and 24 hours after surgery. Results

A total of 1783 patients were delivered by cesarean section over a 203-day period (average of 8.8 cesarean sections/day), and 304 patients (17.0%) developed

696

Faro, Phillips, and Martens

,,.

Table III. Anaerobic bacteria isolated from patients with polymicrobial endometritis*; total isolates = (;ram-pnsitive ort;animl.\ isolated

Gram-negatiw organisms isolated

No. isolated

Rarteroides hh•iu.1 Rarteroides species Fu.10/mctnium nnrlmtum Barteroid,•s fragili.' /iartervidn me/anirzot;enifiL\. Bacteroides di.,iem llartnoidn intennediu1

4 2 I

l'rptvstreptororcu' ~pecies ( ;affkya ruwembza Uo.midium jJerfringms

fi~'

I

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -------·*Specimens taken from endometrium.

Table IV. Bacteria isolated from postoperative wound infections Polwnicrobial infection.\ (total isolates = 17)

Unimicrobial infections (total isolates = 8) Aerobic organisms isolated

No. isolated

Aerobic organisms isolated

Staphylococcus epidermidis Staphylococcus aureu.1 Streptococcus faecalis Streptococcu.s agalactia£ Escherichia coli

3

Staphylococcw aurezH Staphyloroccus epidermidis Streptococcus faecalis Streptococcw agalactiae Enterobacter aerogenes Proteus mirabili.1 Pseudomonas aeruginosa

2 l I l

postpartum endometritis. Endometritis was classified bacteriologically as unimicrobial (83 cases, or 27.3%), polymicrobial (166 cases, or 54.6%), and no growth (55 cases, or 18.1 %). The bacteria isolated most frequently from the endometrium in patients with unimicrobial infection were Streptococcus Jaecalis (40% ), followed by Streptococcus agalactiae (12% ). Members of the Enterobacteriaceae accounted for approximately 23% of the unimicrobial isolates (Table 1). The most frequently isolated anaerobe was Bacteroides, which accounted for eight of 11 isolates (Table I). The most frequently isolated bacterium from the endometrium of patients with polymicrobial infection was S. faecalis, which accounted for approximately 30% of 262 aerobic isolates (Table II). The genus Bacteroides accounted for 80% of anaerobic isolates. The most frequently isolated species was Bacteroides bivius (Table Ill). A total of 543 patients who underwent delivery by cesarean section were analyzed for wound infection. The number of wound infections was 30 for an incidence of 5.5%. The wound infections were grouped according to whether bacteria were cultured from specimens taken from the wound and whether the infection was unimicrobial or polymicrobial. Specimens from 12 (40%) wounds did not yield growth, whereas 10 (33.3%) wounds produced growth of only one bacterium each and eight (27%) wounds were infected by more than one organism. Gram-positive aerobic bacteria were the most frequent organisms recovered from unimicrobial wound infections (Table IV). Polymicrobial

Anaerobic organisms isolated 5 :l 2

No.

~mlated

Bacteroides biviu.s Bacteroides melaninogenicu.' Fusobacterium nucleatum

wound infections involved both gram-positive and gram-negative aerobic and gram-negative anaerobic bacteria. The gram-positive organisms accounted for 79% of aerobic bacteria and gram-negative bacteria accounted for 21% (Table IV). Of the 304 patients with endometritis, 201 specimens were cultured for Mycoplasma species U. urealyticum, and C. trachomatis. Fifteen (7%) patients were colonized with Mycoplasma species, 54 (27%) were colonized with U. urealyticum, and 77 (38%) were colonized with both lHycoplasma species and U. urealyticum. Ten (5%) patients had positive cultures for C. tmchomatis, Mycoplmma species, and U. urealytinan. Three patients had positive cultures for C. trachoma/is and U. urealyticum, two patients had C. trachomatis alone, and one patient had C. trachomatis plus Mycoplasma species. Thus the prevalence of these organisms either alone or in combination was 51% (I 03/20 I) for Mycoplasma species, 72% (144/201) for U. urealyticum, and 8% (16/201) for C. trachoma tis. Of the patients surveyed, a subset of 85 patients who were initially positive for either Mycoplasma species or U. urealyticum or C. trachomatis had another culture taken after treatment for postpartum endometritis with either ticarcillin/davulanate or dindamycin plus gentamicin. Of 30 patients treated with ticarcillin/ clavulanate and positive for Mycoplasma species, 17 (57%) had negative results on reculture. Of 56 patients positive for U. urealyticum, 14 (25%) had negative results on reculture. Of five patients positive for C. tmchomatis, all had negative cultures after treatment with ticar-

Bacteriology of postop ob-gyn infections

\'olume 158 !\umber 3, Pan 2

697

Table V. Influence of antibiotic prophylaxis on genital tract flora in patients undergoing vaginal hysterectomy Preantibiotic Bacteria recovered

Cefoxitin

Staphylococcus aureus epidermidis Streptococcus agalactiae Streptococcus faecalis Enterobacter species Escherichia coli Klebsiella pnewnoniae Bacteroides biviu< Bacteroides species Peptostreptococcus species

31 10 21 22 3

Staph_~lococcus

I

I 18 31 4I 12

Postantibiotic Penicillins

Cefoxitin

20 10 16 20 3 4 I3 27 I9 2I

II 7 H 69 23 8 15 7 9

I

Penicillins 24 R 21 37 4

IR 3R 17 27 7

2

Table VI. Microbiology of patients who developed vaginal cuff cellulitis after antibiotic prophylaxis Antibiotic proph~la:.;is Bacteria

Cefoxitin

M ezlocillin

Penicillin

Streptococcus agalactiae S. faecah< Staphvlococcus aureus Citrobacter diversus E. coli E nterobacter aerogenes E nterobacter cloacae Klebsiella pneumoniae B acteroide.1 assacharol~ticus Bacteroides disiens Bacteroides fragilis Bacteroides melaninogenicus

()

0 2 2

I I

9 0 0

()

()

()

3

2 3

()

2 2 0

()

()

()

{)

I I I

()

()

()

2

()

I

{) ()

cillin/ clavulanate. Thirty-two patients treated with clindamycin plus gentamicin had positive cultures for Mycoplasma species. Twenty-six (81 %) had negative cultures after therapy. Of 36 patients with positive cultures for U. urealyticum, 18 (50%) had negative cultures after therapy. Three patients with positive cultures for C. trachoma/is had negative cultures on reculture. A smaller number of patients who were treated with cefoxitin for postpartum endometritis had cultures taken before and after therapy. Of five patients positive for Mycoplasma species, three remained culture positive. Of eight patients with positive cultures for U. urealyticum, seven remained positive after therapy. Two patients who were culture positive for C. trachvmatis had negative findings after therapy with cefoxitin. In comparing pre- and postantibiotic vaginal cuff cultures in patients undergoing vaginal hysterectomy, changes in the microflora were observed. Patients exposed to three doses of cefoxitin demonstrated a threefold increase in colonization by S. faecalis, whereas among the patients receiving a semisynthetic penicillin, the increase in colonization by S. faecalis was not as great (Table V). Among patients receiving cefoxitin an eightfold increase in colonization by Enterobacter was found.

I

This effect was not observed in the group receiving a semisynthetic penicillin. However, a fourfold increase in Escherichia coli and a threefold increase in Klebsiella pneumoniae colonization was observed in the latter group. Patients receiving cefoxitin prophylaxis demonstrated a significant decrease in anaerobic colonization. The semisynthetic penicillins did not have a suppressive effect in colonization by Bacteroides but caused a decrease in Peptostreptococcus colonization (Table V). In comparing patients receiving different prophylactic agents who subsequently developed postoperative vaginal cuff cellulitis after vaginal hysterectomy, it was noted that S. faecalis was isolated three to four times more frequently from patients who received cefoxitin than the group receiving a semisynthetic penicillin (Table VI). In addition, Enterobacter was isolated from the cefoxitin group but not the semisynthetic penicillin group. The group receiving a semisynthetic penicillin was infected with E. coli, C. diversus, and anaerobes (Table VI). Thus these characteristics are consistent with the postantibiotic prophylaxis microflora noted in the population studied in general. Results of the pilot study to determine the effect of prophylactic agents on normal vaginal flora revealed

698

Faro, Phillips, and Martens Am .J ObHcl Cvr<'

Table VII. Quantitative recovery of normal vaginal flora before and after antibiotic prophylaxis

---------,--------------,------------..----------------·•'< Cefazolin

Prl'operative Lactobacillus

I = 10' 1 = 10'' ~>

Totals Streptococcus faecalts

I

Postoperative

Preoperative

1 ~ IO" 1> 10''

2::;:; 10'

2 2

2

I

= 10'

I~

I

4

4

that Lactobacillus was initially recovered from four of five patients undergoing cesarean section and who received cefazolin for prophylaxis (Table VII). Lactobacillus was recovered from two of those patients 24 hours after surgery. S. faecalis was initially recovered from four of five patients who received cefazolin. That organism was recovered from all four patients 24 hours after surgery. Lactobacillus was initially recovered from four of five patients who received cefoxitin prophylaxis for cesarean section (Table VII). That organism was not recovered from any of those patients 24 hours after surgery. S. faecalis was recovered fi·om four of five patients who received cefoxitin prophylaxis. That organism was recovered from all four patients plus the fifth patient 24 hours after surgery. Lactobacillus was initially recovered from eight of nine patients who received cefotetan prophylaxis for cesarean section (Table VII). It was recovered from all eight patients 24 hours after surgery. S. faecalis was recovered frofll six of nine patients who received cefotetan prophylaxis. It was recovered from eight of nine patients 24 hours after surgery. Similar patterns of recovery were observed from patients who received cefoxitin or cefotetan for prophylaxis before vaginal hysterectomy. A representative sam piing of the predominant pathogens isolated from patients with postoperative pelvic infection was tested in vitro against first-, second-, and third-generation cephalosporins. The results are presented in Table VIII. Good in vitro activity (>85% susceptible) was observed with all antibiotic-organism combinations with the following exceptions: B. bivius and cefonicid and cefuroxime: Enterobacter cloacae and all antibiotics tested; Enterobacter aerogenes and cefazolin, cefonicid, cefotetan, cefoxitin, and cefuroxime; Bacteroides melaninogenicus and cefonicid; Bacteroides fragilis and cefazolin, cefonicid, cefotaxime, and cefuroxime; and Lactobacillus acidophilus and cefotetan and cefoxitin.

Postoperative Not recovered

J(f'

4 10" 10'

0

3~

10"

3

I

10'

1 I

I > 10" Totals

10"

I

= 10'

2=

10''

4

Cefotetan

Cefoxitin

4

~

103 10' 105

5

Preoperative ~ = 3 =

2 2

3

10 IO' IO''

1 > IO' 8 3 ~ 10'' 3 10'

l

Posttpera-:r~. 2 5 I

:

l O' IO' 10''

8 2,; 10" 4 10 1

I = 10'' 6

I 8

10'

Comment Postoperative obstetric or gynecologic infections may be unimicrobial, especially if they occur within the first 24 to 48 hours after the procedure. Postoperative infections are more likely to become apparent on postoperative day 3 or later, and these infections as well as late onset infections are likely to be polymicrobial (mixed aerobic and anaerobic infections). In addition to external risk factors, the status of the internal environment of the patient's lower genital tract may have predictive value concerning the potential for the development of postoperative infection. For example, the pH of the vagina in a healthy state is between 3.8 and 4.2. Simply determining the pH of the vagina can give a clue to an abnormal state, for example, a pH >5 will suggest a decrease in Lactobacillus and the probable presence of organisms, such as Gardnerella vaginalis or Trichomonas vaginalis, which are usually associated with a high anaerobic count. Microscopic examination of the vaginal discharge can also be of predictive value. The presence of clue cells and an absence of white blood cells and free-floating bacteria will suggest G. vaginalis vaginitis, whereas the presence of clue cells, many white blood cells, and free-floating bacteria suggest anaerobic bacterial vaginitis. Attention to these preoperative details can often identify the patient with an endogenous risk for postoperative pelvic infection and facilitate the choice of an appropriate antibiotic for prophylaxis. In choosing the appropriate antibiotic for prophylaxis, the following factors must be considered: spectrum of antibacterial activity, cost, and potential for adverse side effects. Thus far there have not been any significant differences in efficacy noted among the numerous published antibiotic prophylaxis studies.'·'" The studies have focused on comparing cephalosporins and penicillins administered in three doses. Firstgeneration cephalosporins have proved effective bec~use they have relatively broad spectrum of activity against gram-negative facultative anaerobes, gram-

a

\'olumc 158 :\umhcr :), Part

Bacteriology of postop ob-gyn infections

699

~

Table VIII. Susceptibility patterns of isolates from the female genital tract Organism tested I No. tested Escherichia coli, 30 Enterobacter cloacae, 20 Enterobarter aerogenes, I 0 Proteus rnirabilis, 15 Lactohncillus spe-

Cefuroxirne

100 0

100 5

100 70

100 75

100 40

100 0

100 63

100 79

93 25

0

10

90

100

30

0

90

100

10

87 100

87 83

93 100

100 100

93 46

93 47

100 90

100 96

79 96

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

100

90

90

90

100

90

98 93

50 20

100 100

100 100

100 100

100 100

100 93

87 100

52 100

30

10

90

80

100

100

100

90

22

100

100

93

86

100

100

100

100

86

100

100

100

100

100

100

100

100

100

cies, 30 Streptororcw. agalactiae species, 15 Streptocorws fl.vogenes, 10 Staph,•lococrus aurew, 10 Bacteroides bivius, 30 Bacteroides melaninogenicus. 15 Bacteroides fmgilis, 10 PefJtostreptococru.s

species, 14 Clostridium fletfringens, 5

Breakpoints: ,: Hi = susceptible; 232 = resistant; drugs: cefazolin, cefonicid, cefoxitin, cefuroxime, cefazolin, and cefonicid. Breakpoints: :s32 = susceptible; 264 = resistant; drugs: cefoperazone, cefotaxime, cefotetan, ceftizoxime, and ceftriaxone.

positive bacteria, and many anaerobes (Table VIII). However, the administration of three doses of a cephalosporin or penicillin results in changes in the types of bacteria that colonize the lower genital tract as pointed out in the present and previous reports. 11 . 1" Cephalosporins tend to cause increased colonization by S. Jaecalis and Enterobacter. When cefoxitin is the prophylactic agent, there is also a decrease in anaerobes and in commensal bacteria, such as Lactobacillw. If a penicillin is chosen, there is a decrease is some gramnegative bacteria but a significant increase in E. coli, which is commonly involved in pelvic infections and is also a frequent cause of cystitis and pyelonephritis in the obstetric patient. A slightly unusual pattern was observed in the results from the pilot study on vaginal flora. Those antibiotics that have little effect in vitro on S. Jaecalis appeared to have little effect on that organism in vivo; that is, patients who were colonized with S. Jaecali.s at the time of prophylaxis were still colonized 24 hours after prophylaxis with either cefazolin, cefoxitin, or cefotetan. Cefazolin demonstrates good in vitro activity against Lactobacillus, and that organism was eradicated in half the patients initially colonized. On the other hand, neither cefoxitin nor cefotetan demonstrates very good in vitro activity against Lactobacillw. However, Lactobacillus persisted in patients who received cefotetan prophylaxis and was eradicated in patients who received cefoxitin. The isolates recovered from

these patients were resistant to both antibiotics. The fact that three doses of cefoxitin were given compared with one dose of cefotetan may in part account for this observation. The high rate of recovery of Mycoplasma species and U. urealyticum suggests that these organisms are part of the bacterial flora of the patient population studied. As such they can be regarded as potential pathogens in female pelvic infections, just as any other members of the endogenous microflora. The results of posttherapy cultures suggest that ticarcillin/ clavulanate and other broad-spectrum penicillins are not effective in the eradication of Mycoplasma species or U. urealyticum. Ticarcillin/clavulanate appears to be effective in the er;ldication of C. trachomatis. To what extent C. trachomatis contributed to post-operative infections in our patient population is under investigation. No definite conclusions can be derived from the small number of patients who were positive for Mycoplasma species, U. urea(vticum, or C. trachomatis and who were treated with cefoxitin. These preliminary results suggest that cefoxitin is not very effective in eradicating Mycoplasma species and U. urealyticum. The results reported with cefoxitin and C. trachomatis are in conflict with reports of other studies'' and requires further investigation. It was also noted that clindamycin was effective in the eradication of Mycoplasma species and C. trachomatis. Thus patients receiving antibiotic prophylaxis who subsequently develop postpartum endometritis after

700

Faro, Phillips, and Martens

cesarean section or pelvic cuff cellulitis after hysterectomy are likely to be infected by bacteria that are resistant to the antibiotic used. A second possible explanation may be that the infecting bacteria may have minimal inhibitory concentrations in the intermediate range of susceptibility and that standard antibiotic dosing may be ineffective. Therefore if a patient has received a cephalosporin for prophylaxis and subsequently develops a postoperative infection, the patient can be treated with either a semisynthetic penicillin, a broad-spectrum cephalosporin, or combination therapy such as clindamycin or metronidazole plus an aminoglycoside. Many studies have shown that postpartum endometritis can be successfully treated with a single antibiotic of appropriate spectrum.'"· r···" The resistant organisms most likely present in patients treated with a broad-spectrum cephalosporin who do not respond are S. faecalis and in some instances Enterobarter. It has been our experience that S. faecalis is most frequently the offending organism.'' Since most of the used expanded spectrum cephalosporins (cefoxitin, cefotetan, and ceftizoxime) have excellent anaerobic coverage as well as activity against gram-negative facultative anaerobes, ampicillin could be added to provide activity against S. faecali.l. If a patient is bacteremic or has septicemia caused by S. faecalil, then ampicillin and an aminoglycoside should be administered to achieve synergistic activity. Patients allergic to penicillin should be given vancomycin. There are advantages and disadvantages to the selection of any of the aforementioned antibiotics. It is incumbent on the physician to know the weaknesses and strengths of each regimen. Perhaps the use of single doses of antibiotics for prophylaxis will decrease selective pressure on the microflora of the lower genital tract toward those bacteria that are resistant or moderately susceptible to the antibiotic used. The newer cephalosporin agents offer the characteristic suited for single-dosage prophylaxis in that they have an extended half-life. In addition. they have a broad spectrum of activity that makes them attractive agents for treatment. Furthermore, they are easier to administer and may be cost-effective since they require reduced nursing time.

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\lard1 l 'lHS Am.! Ob.,tct (:,,we,[

2. Tramer J. Inhibitory effect of Lactobacillus acidophilw. Nature (London) 1966;211 :204-5. 3. Barefoot SF. Klaenhammer TR. Detection and activitv of lactacin 13, a bacteriocin produced by Lactobaci/lu.1 acidophilw. Appl Environ Microbial 19R3;45:1808-15. 4. Petersen EE. Disturbed vaginal flora as a risk factor in pregnancy. J Obstet Gynecol 1986;6(suppl 1) :S 16-i:l. 5. Lennette EH. ed. Manual of clinical microbiology. Washington, D.C.: American Society f(Jr 'v!icrobiolog;·, 198.7. 6. Phillips LE. Goodrich KL, Turner RM, Faro S. Isolation ofMycofJ/asma species and Ureaplasma urea(vticwn from obstetrical and gynecological patients by using commercially available media formulations. J c.Jin Microbiol I 'l811: 24:377-9. ' 7. Phillips LE, Faro S. Smith PB, Riddle GD, Goodrich KH. Martens MG. Comparison of Monofluor to Microtrak and culture for detection of Chlmn~dia trachoma/is in adolescent out-patients. Br J Vener Dis .. (In press.) 8. Benigno BB, Evrard JR. Faro S, et a!. A comparison of piperacillin, cephalothin and cefoxitin in the prevention of postoperative infections in patients undergoing vaginal hysterectomy. Surg Gynecol Obstet 1986; 163:421-7. 9. Benigno BB. Ford LC:, Lawrence WD. Ledger \V.]. Ling FWL, McNeeley SG. A double-blind, controlled comparison of piperacillin and cef(Jxitin in the prevention of post· operative infection in patients undergoing cesarean section. Surg Gynecol Obstet 1986; 162:1-6. 10. Wideman GL. Matthijssen C. Comparative efficac; ol ccfotaxime and cefazolin as prophylaxis against infections following elective hysterectomy. C:lin Ther 1982:5:67-7cl. 11. Stiver H(~. Forward KR, Tvrrdl DL. et a!. Comparative cervical microflora shifts after cefoxitin and cef:m>lin pro· phylaxis against infection following cesarean section. AM J 0!\SH:r GYM:C:CJL 1986;149:718-21. 12. Faro S. Cox S~l. Phillips LE. Baker JL. InHuenu.: of antibiotic prophylaxis on vaginal minoflora. J Obstet (~y­ naewl 19H6;6(suppl 1):.74-6. 13. Faro S. Phillips LE. BakerJL. (~oodrich KL. Turner RM. Riddle GD. Comparative efficacy of rnezlocillin ,·ersus cefoxitin versus dindamycin plus gentamicin in the treatment of patients with postpartum endometritis. Ohstet Gvnecol 19H7;69:760-6. 14. :\1,artin DH, Pastorek J(;, Faro S. In-vitro and in-vi1o ac· tivity of parenterally administered b-lactam antibiotics against Chlamydia tmrlwmali.,. Sex Trans Dis 1986:13: 81-7. 15. Gilstrap LC III, Maier RC, Gibbs RS, Connor KD, St. Clair P.J. Piperacillin versus dindamycin plus genta· micin for pelvic infections. Obstet Gynecol 1984;64: 71>2-6. 16. Rosene K, Eschenbach DA, Tompkins LS, Kenny GE, Watkins H. Polymicrobial early postpartum endometritis with facultative and anaerobic bacteria, genital AJvroplasmas and ('Jdamydin tmrlwmfltis. Treatment with piperacillin or <.efoxitin. J Infect Dis 1986; 153: I 02H<\7. 17. Faro S. Sanders CV, Aldridge KE. Lise of single agent antimicrobial therapy in the treatment of polymicrobial female pelvic infections. Obstet (;mecol 1982;60:232-6.