Bacteroides bivius and Bacteroides disiens in obstetrical patients: clinical findings and antimicrobial susceptibilities

Piperacillin/tazobactam in the treatment of polymicrobial infections

Polymicrobial infections are characterized by the presence of micro-organisms from more than one group of bacteria. Empirical treatment of polymicrobial infections requires an agent active against both anaerobic and aerobic/facultative bacteria. An aminoglycoside used in combination with an anti-anaerobe agent is commonly used to treat polymicrobial infections. However, aminoglycoside nephrotoxicity and treatment failures raise questions about the use of such regimens. Among non-aminoglycoside treatment regimens such as penicillin and cephalosporins, effectiveness has been compromised by bacteria producing extended spectrum beta-lactamases. Cefoxitin shows satisfactory results for treatment of intra-abdominal infections. Other studies have shown good results with imipenem, cefotetan and piperacillin used as single agents. Piperacillin/tazobactam, a new combination broad-spectrum antibiotic and potent beta-lactamase inhibitor, can be used for the treatment of infections caused by piperacillin-sensitive micro-organisms as well as beta-lactamase-producing, piperacillin-resistant organisms. This broad-spectrum activity is appropriate for infections traditionally treated empirically by double or triple antibiotic therapy.

Activity of trospectomycin against Bacteroides fragilis and other Bacteroides species

The in vitro activity of trospectomycin (U-63366; 6'-n-propyl spectinomycin pentahydrate sulfate) was evaluated against 189 clinical isolates of the Bacteroides fragilis group and 65 Bacteroides species isolates. At less than or equal to 8 micrograms/ml, the activity of trospectomycin compared favorably with those of clindamycin and cefoxitin against B. fragilis, Bacteroides distasonis, and Bacteroides vulgatus, and there was no cross resistance to these three drugs among the strains of the B. fragilis group. All the Bacteroides species were susceptible to trospectomycin. The results of this in vitro study indicate that trospectomycin possesses excellent activity against Bacteroides species.

Ampicillin/sulbactam versus metronidazole-gentamicin in the treatment of soft tissue pelvic infections

The clinical efficacy and safety of ampicillin/sulbactam versus metronidazole-gentamicin were evaluated in a comparative, randomized, prospective study. Forty-four patients were enrolled: 22 received the ampicillin/sulbactam regimen, and 22 received the metronidazole-gentamicin combination. There were 33 cases of severe acute pelvic inflammatory disease, two tuboovarian abscesses, five cases of endomyometritis, and two cases of posthysterectomy pelvic cellulitis. Aerobic and anaerobic cultures from the infection sites yielded 447 microorganisms from 44 patients (an average of 10 bacteria per infection; 6.4 anaerobes and 3.7 aerobes). The most frequent isolates were Bacteroides sp., 54; Bacteroides bivius, 17; black-pigmented Bacteroides, 12; Bacteroides disiens, 11; Fusobacterium, 13; Peptostreptococcus anaerobius, 24; Peptostreptococcus asaccharolyticus, 21; anaerobic gram-positive cocci, 34; Gardnerella vaginalis, 29; Neisseria gonorrhoeae, 17; alpha-hemolytic streptococci, 15; and Escherichia coli, five. Clinical cure was noted in 19 of 20 patients treated with ampicillin/sulbactam and 18 of 21 patients treated with metronidazole-gentamicin. One treatment failure occurred in the ampicillin/sulbactam group in a patient who required antichlamydial therapy and had a complex left adnexal mass consistent with an abscess. The cases of metronidazole-gentamicin failure included two patients initially diagnosed as having tuboovarian abscesses who required a change in antibiotic therapy to control the infections. The third patient had postabortion endomyometritis that did not respond to metronidazole-gentamicin therapy within 48 hours, and required a change of medication. No adverse hematologic, renal, or hepatic effects were noted in either group of patients.

Microbiology of the female genital tract

Patients who contract genital tract infections are predominantly young, are otherwise healthy, and generally respond well to treatment for bacterial infections. These infections are most commonly polymicrobial in etiology, with several noteworthy exceptions. Often there is an inciting event such as childbirth, surgical intervention, pregnancy termination or intrauterine contraceptive device insertion. With treatment, prognosis for cure is excellent; however, sequelae such as recurrent infections, infertility, or ectopic pregnancy can be serious. Bacteria encountered in the female genital tract can be divided into aerobic and anaerobic organisms. Among the aerobic gram-positive organisms, several varieties of streptococci such as Group B streptococci and enterococci occur frequently. Staphylococcus aureus is an infrequent but important pathogen. Among the aerobic gram-negative organisms, the most common is Escherichia coli. Klebsiella sp. and Proteus sp. occur in about 5% of genital tract infections. Species that are more resistant to antibiotics, such as Pseudomonas aeruginosa and Enterobacter sp., occur in approximately 1% or 2% of these cases and are more likely to appear in patients who have previously received antibiotic therapy or who have been hospitalized for some time. Among the anaerobic organisms, the most common gram-positive isolates are Peptostreptococci and Peptococci. Clostridia sp. occurs less frequently. Among the anaerobic gram-negative organisms, the Bacteroides sp. most frequently encountered are Bacteroides bivius and Bacteroides disiens. Bacteroides fragilis is still a common problem but appears to be less predominant. Other organisms encountered are Chlamydia trachomatis, the genital mycoplasmas, yeasts, protozoa, and viruses.

Inactivation of cefoxitin and moxalactam by Bacteroides bivius beta-lactamase

Moxalactam and cefoxitin are known for their high stability against Bacteroides beta-lactamases. We investigated the beta-lactamase activity of crude extracts obtained from three strains of Bacteroides bivius and two strains of Bacteroides fragilis against cefoxitin and moxalactam. In a spectrophotometric antibiotic assay with a 24-h incubation period, B. bivius extracts decreased the initial concentration (10 micrograms/ml) of moxalactam and cefoxitin by 60%, whereas B. fragilis extracts had no effect. In a microbiological assay, when B. bivius or B. fragilis extracts were added to cephalothin (10 micrograms/ml) or cefamandole (4 micrograms/ml), we observed complete disappearance of the inhibitory zones against the indicator strain (Clostridium perfringens ATCC 13124). Only the B. bivius extracts were able to decrease the inhibitory activity (from 10 to 100%) of cefoxitin and moxalactam (each at 10 micrograms/ml). Prior addition of clavulanic acid to crude extracts prevented the losses of antibacterial activity. Furthermore, the inhibition of the beta-lactamase hydrolysis of nitrocefin by cefoxitin or moxalactam was prevented by a 12-h preincubation of the beta-lactam with the B. bivius extracts but not with the B. fragilis extracts. Finally, with the B. bivius strain producing the most beta-lactamase, we showed an effect of inoculum size on the MICs of cefoperazone, cefoxitin, and moxalactam with a broth dilution technique. Increasing the inoculum size with the B. fragilis strains had no effect on the MISs of cefoxitin and moxalactam. These results indicate a slow and clavulanate-sensitive beta-lactamase activity of B. bivius extracts against cefoxitin and moxalactam.

Survey of anaerobic susceptibility patterns in Canada

The in vitro activity of penicillin, cefoxitin, moxalactam, ticarcillin, clindamycin, chloramphenicol, and metronidazole against 590 anaerobic isolates collected from five Canadian hospitals during 1984 was determined by an agar dilution technique. Cefoxitin, clindamycin, chloramphenicol, and metronidazole were very active against most of the isolates. No major regional differences in the susceptibility patterns were observed.

Moxalactam versus clindamycin plus tobramycin in the treatment of obstetric and gynecologic infections

The clinical efficacy of moxalactam versus clindamycin/tobramycin was evaluated in a comparative, randomized, prospective study. Sixty patients were treated: 30 with moxalactam and 30 with clindamycin/tobramycin. There were 15 cases of tuboovarian abscess, 36 cases of severe pelvic inflammatory disease with peritonitis, eight cases of endomyometritis, and one wound abscess. Aerobic and anaerobic cultures from the sites of infection yielded 441 microorganisms from 53 patients; an average of 8.3 bacteria per infection (4.5 anaerobes and 3.8 aerobes). The infections tended to be mixed aerobic-anaerobic with anaerobes isolated in 90% of cases. The most frequently isolated possible pathogens were Bacteroides sp. (37), Bacteroides bivius (23), Bacteroides asaccharolyticus (12), Peptococcus asaccharolyticus (29), Peptostreptococcus anaerobius (19), unidentified anaerobic gram-positive cocci (18), Escherichia coli (17), nonhemolytic streptococci (16), Neisseria gonorrhoeae (13), and Gardnerella vaginalis (38). Clinical cure was noted in 29 of 30 moxalactam-treated and 29 of 30 clindamycin/tobramycin-treated patients. Moxalactam was effective in five of six cases of tuboovarian abscess, all 22 cases of pelvic inflammatory disease with peritonitis, the one case of endomyometritis and the one wound abscess. Clindamycin/tobramycin was effective in eight of nine cases of tuboovarian abscess, all 14 cases of pelvic inflammatory disease with peritonitis, and all seven cases of endomyometritis. No adverse hematologic, renal, or hepatic effects were noted with either regimen.

Therapy of mixed anaerobic-aerobic infections. Lessons from studies of intra-abdominal sepsis

Mixed anaerobic-aerobic infections may occur in a variety of anatomical locations and are usually related to the spread of bacteria from a proximal mucosal surface. Much has been learned about the pathophysiology and treatment of mixed anaerobic-aerobic infections from the study of intra-abdominal sepsis related to spillage of colonic contents. There is an average of five microorganisms at the infected site: three anaerobic and two aerobic pathogens. Appendicitis and diverticulosis are the most common conditions which predispose to fecal contamination of the intra-abdominal cavity. Initially, peritonitis develops which, if untreated, progresses to an abscess. The abscess is a unique pathologic entity which may form a protective environment for the microorganisms and present a barrier to the action of certain antimicrobial agents. Treatment usually involves two modalities: surgical drainage or debridement and appropriate antimicrobial agents to cover both components of the mixed infection. On the basis of in vitro susceptibility there are six groups of antimicrobial agents that are useful in treating intra-abdominal infections: clindamycin; metronidazole; chloramphenicol; broad-spectrum penicillins (carbenicillin/ticarcillin/piperacillin); cephalosporins (cefoxitin/moxalactam); and imipenem. Randomized prospective studies have shown that the first five of these groups are effective in the therapy of intra-abdominal mixed infections. Preliminary data indicate that imipenem/cilastatin is very effective in the therapy of this serious infection; however its place in the therapeutic armamentarium awaits the completion of randomized prospective studies against established drugs.

Antimicrobial susceptibilities of anaerobic bacteria isolated from female genital tract infections

Certain species or subspecies of anaerobic bacteria are isolated with higher frequency from female genital tract infections than from other anatomic sites. To gain susceptibility data more specific to the treatment of these infections, nine antimicrobial agents were tested by an agar dilution technique against 230 anaerobic bacteria isolated solely from obstetric and gynecological infections. These genital isolates were, in general, very susceptible to imipenem (most active, inhibiting all gram-negative rods at less than or equal to 1 microgram/ml), clindamycin (all isolates inhibited at less than or equal to 4 micrograms/ml), metronidazole (all gram-negative rods inhibited at less than or equal to 4 micrograms/ml), and chloramphenicol. Penicillin G had generally low activity against Bacteroides spp., not restricted to just the Bacteroides fragilis group, although it was very active against gram-positive species. Bacteroides bivius, a species uniquely common in female genital infections, was particularly resistant (90% MIC, 64 U/ml). Also, the Bacteroides melaninogenicus isolates were less susceptible than previously reported for isolates not exclusively from genital sites. Compared with moxalactam, cefotaxime, and cefoperazone, cefoxitin usually demonstrated equal or greater activity against most Bacteroides spp., with the exception of greater activity of moxalactam against B. fragilis (formerly subsp. fragilis). Resistance to moxalactam was observed among strains of Peptostreptococcus anaerobius, a common genital isolate. Overall, the activities of these four drugs were not as predictable as those observed for clindamycin, metronidazole, chloramphenicol, and imipenem.

Role of Bacteroides bivius beta-lactamase in beta-lactam susceptibility

The susceptibility of 46 clinical isolates of Bacteroides bivius to amoxicillin, cefotaxime, cefoxitin, ceftizoxime, cephaloridine, cephalothin, moxalactam, penicillin G, amoxicillin plus clavulanic acid in a ratio of 2:1, carbenicillin, cefamandole, and ceftazidime was determined by an agar dilution technique. For the first eight agents susceptibility testing was also done with the addition of clavulanic acid (0.75 microgram/ml). For all agents, beta-lactamase-positive strains (35, using a nitrocefin slide test) were inhibited at higher concentrations than beta-lactamase-negative strains. Clavulanic acid reduced the susceptibility of the beta-lactamase-positive strains to the level of the beta-lactamase-negative strains to all agents. We prepared crude extracts of beta-lactamase from six strains. Activity against nitrocefin was directly related to their susceptibilities. The beta-lactamase had a mixed-substrate profile, hydrolyzing both penicillins and cephalosporins. Our results suggest a slow inactivation of cefoxitin, ceftizoxime, and moxalactam by the beta-lactamase. Clavulanic acid and cefoxitin inhibited the enzyme, whereas p-hydroxymercuribenzoate and cloxacillin did not. Thus, there was a clear relationship between beta-lactamase activity and susceptibility to beta-lactams, including cefoxitin and third-generation cephalosporins. The substrate and inhibition profiles of the B. bivius beta-lactamase were different from those of enzymes found in the "B. fragilis group."

Comparison of the activities of penicillin G and new beta-lactam antibiotics against clinical isolates of Bacteroides species

MICs were determined for 218 clinical isolates of Bacteroides by a broth microdilution method. Imipenem was the most active antibiotic tested. Azlocillin, mezlocillin, and cefoxitin had comparable activities, with resistance among members of the B. fragilis group and B. capillosus. Ceftizoxime was the most active cephalosporin tested. Members of the B. fragilis group showed high levels of resistance to cefotetan and ceftazidime. Resistance to penicillin G varied from 0 to 14%.

Comparative study of piperacillin versus cefoxitin in the treatment of obstetric and gynecologic infections

Piperacillin sodium (Pipracil, Lederle Laboratories, Wayne, New Jersey), a new semisynthetic penicillin, demonstrated in vitro activity against a broad spectrum of clinical pathogens. It is active against most strains of the clinically important gram-negative aerobic or facultative bacteria and against virtually all the clinically important anaerobic organisms, including Bacteroides fragilis and Bacteroides bivius. This broad antibacterial spectrum suggested that piperacillin might be an effective single antimicrobial agent for the treatment of mixed aerobic/anaerobic infections in obstetric and gynecologic patients. In this study, the clinical efficacy and safety of piperacillin was compared with that of cefoxitin in the management of pelvic infections. There were 23 patients in the piperacillin group (acute salpingitis, 12; endomyometritis, 7; pelvic cellulitis, 2; tuboovarian abscess, 2) and 25 patients in the cefoxitin group (acute salpingitis, 13; endomyometritis, 10; tuboovarian abscess, 2). An average of six bacteria were isolated from each patient. Aerobic bacteria only were recovered from 12.5%, anaerobic bacteria only in 6.5%, and both aerobic and anaerobic bacteria were present in 82.5% of patients. Overall, 21 of 23 (91%) of the piperacillin treatment group and 23 of 25 (92%) of the cefoxitin group responded to therapy with antimicrobial agents alone. The major cause of failure was the presence of an abscess. Piperacillin was shown to be an effective single agent for the management of pelvic infections caused by mixed aerobic and anaerobic bacteria. In addition, piperacillin proved to be safe and well tolerated.

The vaginal microbial flora in non-specific vaginitis

The facultative and strictly anaerobic vaginal microbial flora was investigated in 40 women with non-specific vaginitis and in 40 control women seen in private gynaecological practice. Gardnerella vaginalis, anaerobic gram-negative bacilli, anaerobic gram-negative and gram-positive cocci were all associated with non-specific vaginitis (p less than 0.001), whereas lactobacilli occurred less frequently in non-specific vaginitis than in controls (p less than 0.01). The most common anaerobes were Veillonella parvula, Bacteroides bivius, Bacteroides assaccharolyticus, Bacteroides capillosus and Peptococcus asaccharolyticus. Anaerobic gram-negative curved rods were found in 11% of cases of non-specific vaginitis. A characteristic pattern of short chain organic acids was found on gas liquid chromatographic analysis of vaginal secretions in non-specific vaginitis. A succinate/lactate peak ratio of 0.3 or more was found in 75% of women with non-specific vaginitis (p less than 0.001). Clue cells, a positive amine test, a pH higher than 5.0, and the absence of lactobacilli on a Gram stained vaginal smear strongly correlated with non-specific vaginitis (p less than 0.001).

Infectious complications of cervical cerclage

A study of 115 gravid patients who required cervical cerclage indicated that the optimum time to perform the surgical procedure was between the fourteenth and eighteenth weeks. If the operation is delayed until later in the second trimester, the incidence of chorioamnionitis is increased 2.6-fold, and premature rupture of the membranes prior to the thirty-second week of gestation is trebled. Amniocentesis performed in nine patients with chorioamnionitis and intact membranes after cerclage demonstrated the polymicrobial nature of the amniotic fluid infection. The isolation of such organisms at Bacteroides bivius, Eubacterium lentum, and Staphylococcus epidermidis indicates their potential importance in chorioamnionitis. Early recourse to amniocentesis is recommended when chorioamnionitis is suspected, and, moreover, prophylactic antibiotics should be used when cerclage is performed after the eighteenth week of pregnancy.