Gram-negative anaerobic bacilli: their role in infection and patterns of susceptibility to antimicrobial agents. I. Little-known Bacteroides species

Microbiology and management of polymicrobial female genital tract infections in adolescents

This review describes the microbiology and management of female genital tract infections in adolescents. These infections include vulvovaginitis, vulvovaginal pyogenic infections (abscesses of Bartholin's and Skene's glands, infected labial inclusion cysts, labial abscesses, furunculosis, and hidradenitis), endometritis, pyometritis, salpingitis, pelvic inflammatory disease, and tubo-ovarian and pelvic abscess. Anaerobes can be cultured in 50% to 90% of females with a variety of genital infections and are the exclusive isolates in 20% to 50%. Obligate anaerobes are particularly common in closed-space infections, such as tubo-ovarian and vulvovaginal abscesses. The most common anaerobes found in these infections are gram-negative bacilli (especially P. bivia and P. disiens) and anaerobic cocci. Anaerobes generally are not the only pathogens found, but are usually mixed with aerobes. The most common aerobic pathogens are members of the Enterobacteriaceae family, especially E. coli, and aerobic or microaerophilic streptococci. Sexually acquired infections include Neisseria gonorrhoeae, Gardnerella vaginalis, Trichomonas vaginalis, Chlamydia trachomatis, herpes simplex, and Condyloma accuminata. Treatment regimens must provide antimicrobial coverage for N gonorrhoeae, C trachomatis, anaerobes, streptococci, and gram-negative facultative bacteria.

Prevotella bivia as an unusual cause of endocarditis

A case of monomicrobial endocarditis due to Prevotella bivia in a 60-year-old man without previous cardiac lesions is reported. The extremely indolent course with multiple systemic emboli as the only clinical manifestation occurring at least seven months before diagnosis and the persistently negative blood cultures were remarkable features of this case. The incidence, clinical characteristics, treatment and outcome of published cases of infective endocarditis due to anaerobic bacteria are briefly reviewed.

New findings on the microbial flora associated with adult periodontitis

The predominant microbial flora associated with adult periodontitis was investigated in 21 patients aged 20-40 years. Microorganisms from samples of subgingival plaque were cultured on selective and non-selective media under aerobic and anaerobic conditions. Ten species or groups out of a total of 31 were found to comprise the predominant cultivable flora: diphtheroids, Porphyromonas asaccharolytica, coagulase-negative staphylococci, 'Streptococcus milleri'-group, Bacteroides ureolyticus, Capnocytophaga ochracea, the Prevotella veroralis/buccalis complex, P. intermedia, P. oralis and unidentified Prevotella spp. Two species previously reported at periodontitis sites, namely P. gingivalis and Fusobacterium nucleatum, were not isolated, whereas Prevotella species accounted for the majority of isolates in this investigation. The large proportion of non-pigmented Prevotella species, P. asaccharolytica and B. ureolyticus that were found have not generally been reported previously. The role of these microorganisms and also coagulase-negative staphylococci, diphtheroids and the 'Streptococcus milleri'-group requires further investigation in adult periodontitis.

beta-Lactamase production and susceptibility of US and European anaerobic gram-negative bacilli to beta-lactams and other agents

The susceptibility of 1,476 US and European strains of anaerobic gram-negative bacilli to amoxicillin, amoxicillin/clavulanate, ticarcillin, ticarcillin/clavulanate, cefoxitin, imipenem and metronidazole was determined. All of the Bacteroides fragilis group and 51% of the non-Bacteroides fragilis group were beta-lactamase positive. Amongst the non-Bacteroides fragilis group, beta-lactamase positivity rates were higher for US strains (58%) than for European strains (39%). All strains were susceptible to imipenem and metronidazole. MIC90s of amoxicillin and ticarcillin for all beta-lactamase negative strains were 0.5 and 2 micrograms/ml, respectively. The addition of clavulanate reduced the MIC90s of amoxicillin (> or = 256 micrograms/ml) and ticarcillin (> or = 64 micrograms/ml) to 16 and 8 micrograms/ml, respectively, for the Bacteroides fragilis group, and to 4 micrograms/ml for both agents for the non-Bacteroides fragilis beta-lactamase producing group. Twenty-nine cefoxitin-resistant strains were found, mainly in the Bacteroides fragilis group, while 95 beta-lactamase producing strains (predominantly Bacteroides fragilis group and fusobacteria) did not show synergy between beta-lactams and clavulanate. Of the newe agents tested, meropenem and piperacillin-tazobactam were the most active (100% of strains susceptible), followed by amoxicillin-BRL 42715 (99% of strains susceptible); 94 to 98% of the strains were susceptible to cefoperazone-sulbactam, tosufloxacin, temafloxacin and clindamycin. Only 73% of the strains were susceptible to cefotetan, compared to 91% to cefoxitin; 88% of the strains were susceptible to trospectomycin. Overall, all of the beta-lactam/beta-lactamase inhibitor combinations, imipenem, meropenem, cefoxitin, tosufloxacin, temafloxacin and clindamycin had good activity against beta-lactamase producing strains, while all agents tested had good activity against beta-lactamase negative strains.

Acute intramedullary spinal cord abscess: case report

We report the first case of an acute pyogenic intramedullary cervical spinal cord abscess, brain abscesses and meningitis due to an unusual anerobe, Bacteroides disiens. The importance of spinal magnetic resonance imaging for establishing the diagnosis is emphasized.

Restriction endonuclease analysis and ribotyping differentiate genital and nongenital strains of Bacteroides ureolyticus

Thirty-three clinical isolates from male nongonococcal urethritis and 28 isolates from soft tissue infections and ulcers were identified as Bacteroides ureolyticus by conventional bacteriological tests and were compared with five reference strains of the species. Whole-cell proteins from these clinical isolates and the reference strains were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The majority of the strains from the two sources could be divided into five different groups, named phenons I to V; phenons I to IV have been described previously by others, while phenon V has been described recently by us. Digestion of chromosomal DNA from 16 of the clinical isolates (including strains representative of each of the five SDS-PAGE phenons) and the five reference strains was attempted with restriction endonucleases EcoRI, PstI, SmaI, and HindIII. After electrophoresis in agarose gels, good digestion was observed with HindIII only, and 12 different banding patterns (restriction endonuclease analysis [REA] profiles) were obtained for the 19 strains digested; one nongonococcal urethritis isolate and one reference strain did not show any digestion. From the agarose gels, HindIII-digested fragments of DNA were transferred to nylon membranes by use of vacuum blotting and subjected to hybridization with 32P-labelled 16S-23S rRNA from Escherichia coli. The resultant pattern of bands (ribotypes), which depends on the restriction fragment length polymorphisms in the rRNA genes, was used as a measure of genomic variation within the species. In total, 13 different ribotypes were obtained for the 19 strains. For some strains, good correlation was achieved among the SDS-PAGE phenons, REA profiles, and ribotypes. However, for others, REA analysis and ribotyping were able to discriminate between strains which shared the same SDS-PAGE phenon. Interestingly, these two techniques of DNA characterization were able to differentiate between isolates from the genital tract and those associated with soft tissue infections and ulcers.

The survival of subgingival plaque bacteria in an amine fluoride-containing gel

Subgingival plaque samples from 20 patients with chronic inflammatory periodontal disease were exposed to a commercial gel formulation containing 2 amine fluorides. The MIC of the gel for these samples ranged from 33 to 260 micrograms/ml with a modal value of 260 micrograms/ml. In each sample, the most resistant organisms (i.e., those organisms surviving at one doubling dilution below the MIC) were identified. 33 such organisms were isolated, of which 22 (67%) were strict anaerobes, and 25 (75%) were Gram negative. The 2 most frequent isolates were Bacteroides ruminicola ss. brevis and a Selenomonas species, neither of which is a recognised periodontopathogen. The gel had a rapid effect on the viability of the bacteria in the plaque samples, the 90% kill time being 17 min or less for 90% of the samples (range less than 5 to 71 min).

Beta-lactamase production and susceptibilities to amoxicillin, amoxicillin-clavulanate, ticarcillin, ticarcillin-clavulanate, cefoxitin, imipenem, and metronidazole of 320 non-Bacteroides fragilis Bacteroides isolates and 129 fusobacteria from 28 U.S. centers

beta-Lactamase production (nitrocefin disk method) and agar dilution susceptibility of amoxicillin, amoxicillin-clavulanate, ticarcillin, ticarcillin-clavulanate, cefoxitin, imipenem, and metronidazole were determined for 320 Bacteroides species (not Bacteroides fragilis group) and 129 fusobacteria from 28 U.S. centers. Overall, 64.7% of Bacteroides species and 41.1% of fusobacteria were beta-lactamase positive. Among the Bacteroides species, positivity rates were highest for B. bivius (85.0%), followed by B. splanchnicus (83.3%), B. eggerthii (77.8%), and B. oralis (77.1%); 54.5% of black-pigmented Bacteroides species were beta-lactamase positive. Among the fusobacteria, Fusobacterium mortiferum showed the highest rate of beta-lactamase positivity (76.9%). MICs of amoxicillin (128 micrograms/ml) and ticarcillin (64 micrograms/ml) for 90% of all beta-lactamase-positive strains were reduced to 4 and 2 micrograms/ml, respectively, with the addition of clavulanate. MICs of amoxicillin and ticarcillin for 90% of all beta-lactamase-negative strains were 1 and 4 micrograms/ml, respectively, and greater than or equal to 98.4% of the strains were susceptible to the beta-lactams tested. Of the beta-lactamase-producing strains, 45.9% were susceptible to amoxicillin at less than or equal to 4 micrograms/ml and 93.4% were susceptible to ticarcillin at less than or equal to 64 micrograms/ml; the addition of clavulanate raised the rates to 90.4 and 100%, respectively. All strains were susceptible to cefoxitin, imipenem, and metronidazole. The activity of amoxicillin against 29 beta-lactamase-producing strains (10 Bacteroides species and 19 fusobacteria) was not enhanced by the addition of clavulanate; however, 82.7% of these strains were susceptible to amoxicillin, and all were susceptible to ticarcillin. Although beta-lactamase positivity is on the increase in non-B. fragilis group Bacteroides species and fusobacteria, amoxicillin-clavulanate, ticarcillin, cefoxitin, imipenem, and metronidazole should be suitable for the treatment of infections with these strains. The addition of clavulanate does not appreciably improve the efficacy of ticarcillin against these organisms.

The prevalence of beta-lactamase producing bacteria in subgingival plaque and their sensitivity to Augmentin

Subgingival plaque samples from 20 patients with chronic periodontitis who had received no antibiotics for at least 3 months were screened for the presence of beta-lactamase-producing bacteria. Thirteen of the patients harboured beta-lactamase producing bacteria, most of which were members of the genus Bacteroides. The most frequently isolated species were Bacteroides melaninogenicus and Bacteroides capillosus which are often implicated in acute oral infections. All of the beta-lactamase-producing bacteroides strains were sensitive to a combination of amoxycillin with clavulanic acid (Augmentin).

The microbiology and chemotherapy of odontogenic infections

This article reviews the complexity of the microbiological environment of odontogenic infections. With an understanding of the organisms involved, the appropriate antibiotic can be chosen. A review of current antibiotic choices and the rationale for their selection is also presented.

Bacteroides spp. in dental root canal infections

A summary of a series of bacteriological studies of endodontic infections is presented in this article. The bacteriology of 62 root canal infections was studied with special attention focused on the occurrence, role and taxonomy of Bacteroides spp. All infections except one were mixed infections dominated usually by anaerobic bacteria. Four to 6 different species were present in most canals. Species of the genus Bacteroides were found more frequently than species of any other genus. Seventy-eight Bacteroides strains were isolated from 45 canals. B. buccae, B. intermedius, B. denticola, B. oris, B. oralis, and B. gingivalis were the most common Bacteroides spp. At the beginning of the treatment 35 of 62 teeth caused acute symptoms. The results indicated that symptoms were a result of the synergistic action of the mixed anaerobic flora. The presence of B. gingivalis, B. endodontalis, and B. buccae was more often related to acute cases than other Bacteroides spp. Black-pigmented Bacteroides and a new Bacteroides-like organism, Mitsuokella dentalis, seemed to increase the probability that acute symptoms would persist one week after the beginning of the treatment. However, the treatment result assessed after 4 weeks and after 1 year was not affected by the composition of the mixed anaerobic flora. Calcium hydroxide was the only canal disinfectant used. Its efficacy was proved by a bacteriological sample at the second appointment in 10 cases. All teeth were asymptomatic at the third appointment. The susceptibility of the isolated Bacteroides strains to penicillin G was also studied. Only 2 B. buccae strains and 2 B. denticola strains were resistant at a concentration of 2.4 micrograms/ml. The patients were randomly divided into 3 groups which received 1) no antibiotics, 2) penicillin V (650 mg x 3) for 7 days, or 3) for 12 weeks. There was no difference between the 3 groups in the healing of the periapical lesion after one year. All patients attended the 1-year control. Fifty cases showed complete healing, partial healing was obtained in 11 cases and in 1 case no healing was observed.

Antimicrobic susceptibility of bacterial pathogens from horses

Rational choice of an antimicrobial agent requires that the condition for which the drug is prescribed contain an infectious agent and, if so, knowledge of the susceptibility of the microorganism to antimicrobial drugs. Unfortunately, most infectious conditions necessitate the use of an antimicrobic drug before data from the microbiology laboratory are available. The data presented are meant to serve as a guide in the choice of antimicrobic drugs for treatment of infectious processes of the horse before knowledge of the nature of the microorganism isolated as well as its susceptibility to antimicrobic agents. What has been presented are the most commonly isolated microorganisms together with their susceptibility to antimicrobic drugs.

Numerical analysis of electrophoretic protein patterns of Bacteroides ureolyticus clinical isolates

A total of 37 Bacteroides ureolyticus clinical isolates (mainly from the United Kingdom) comprising 18 nongonococcal urethritis-associated strains and 19 other strains, including the type strain (NCTC 10941T) and strains from abscesses, ulcers, and various other soft tissue lesions, and five reference strains of other Bacteroides, Fusobacterium, Megamonas, and Sebaldella species were characterized by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of cellular proteins. The protein patterns, which contained 45 to 50 discrete bands, were highly reproducible and were used as the basis for a numerical analysis. Four clusters comprising 31 strains of B. ureolyticus were obtained at the 70% similarity level, and one of these was further divided to give two subclusters at the 82% similarity level. The analysis showed that the clusters obtained corresponded with three previously identified polyacrylamide gel electrophoresis types (I, II, and III) within the species, although two slightly different patterns within type I were detected. Evidence is presented for a new protein pattern (type IV) which was characteristic of NCTC 10941T and seven isolates. There was no clear-cut correlation between the pattern type and the clinical source of the isolates, except for the type Ib and type IV strains, which were nongonococcal urethritis-associated and wound isolates, respectively.

Bacteriologic and clinical study of Bacteroides oris and Bacteroides buccae

We characterized clinical isolates previously identified in our laboratory as Bacteroides ruminicola, the human strains of which are now classified as Bacteroides oris and Bacteroides buccae. A total of 72 isolates (55 B. buccae isolates and 17 B. oris isolates) recovered over a 10-year period were studied. They were differentiated from each other by special-potency antibiotic disks and the RapID-ANA system. The two organisms were associated with a variety of infections, the majority being pleuropulmonary (29.2%) and infections of the head and neck region (27.8%). The infections were always polymicrobial, usually with more than five organisms per specimen. A total of 44% of the B. oris strains and 27% of the B. buccae strains were resistant to penicillin G (breakpoint, 2 U/ml), and this correlated with the presence of beta-lactamase. Although B. oris and B. buccae are found with some frequency in human infections, they are present primarily as components of a mixed flora.

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.

In vitro activities of 17 antimicrobial agents against the formate/fumarate-requiring, anaerobic gram-negative bacilli

The in vitro activities of 17 antimicrobial agents were evaluated against 46 clinical isolates of formate/fumarate-requiring anaerobic gram-negative bacilli. Strains of Bacteroides ureolyticus (23) were almost uniformly susceptible to the tested antimicrobials, whereas strains of Bacteroides gracilis (18) showed some striking resistance with penicillin active against only 67%, the cephalosporins active against 67%-89%, and clindamycin active against 67%. Although few strains of Wolinella species/C. concisus (5) were available for testing, these isolates tended to be more resistant than B. ureolyticus but less resistant than B. gracilis.

Occurrence of clindamycin-resistant anaerobic bacteria isolated from cultures taken following clindamycin therapy

MICs of clindamycin were determined by the agar dilution method against anaerobic organisms isolated from endometrial cultures in women with pelvic soft tissue infections. Cultures were obtained from 100 women both before and after clindamycin therapy, from 107 women before therapy with clindamycin or another antimicrobial agent or after treatment with an antimicrobial agent other than clindamycin, and from 9 women 1 to 9 weeks after they were discharged from the hospital following clindamycin therapy. Only 5 (0.7%) of 685 isolates tested from women who had not received clindamycin therapy were resistant to clindamycin. From the 100 cultures taken immediately after clindamycin therapy, 57 anaerobic bacteria were isolated from 28 cultures. Of the 40 anaerobic organisms for which MICs of clindamycin were determined, 25 (62.5%) were resistant to clindamycin (MIC greater than or equal to 8 micrograms/ml). The most common organisms isolated after therapy were the anaerobic gram-positive cocci (of which 32 isolates were discovered); of 28 coccal isolates tested, 64% were clindamycin resistant. Four of seven (57%) of the Bacteroides isolates tested, one unidentified gram-positive nonsporing rod, one unidentified gram-negative coccus, and one Mobiluncus sp. were also clindamycin resistant. Of 18 anaerobic isolates from the nine cultures taken 1 to 9 weeks after hospital discharge, 55% were resistant to clindamycin. The clinical significance of these findings is unknown since all patients recovered without incident and remained well. However, the data suggest that physicians need to be aware that patients with recent exposure to clindamycin may have clindamycin-resistant anaerobic organisms in a current infection. This may prevent the infection from responding to clindamycin treatment.

Bacteroides gracilis, an important anaerobic bacterial pathogen

Clinical isolates of agar-pitting, formate-fumarate-requiring, anaerobic gram-negative bacilli were recharacterized in consideration of the species descriptions of Bacteroides ureolyticus and the newly described B. gracilis, Campylobacter concisus, and Wolinella sp. During an 11-year period, 7.5% (101 of 1,341) of all specimens yielding anaerobes were found to contain an organism in this group. Of the 71 isolates that were available for study, 43 were B. ureolyticus, 23 were B. gracilis, and 5 were in the Wolinella-C. concisus group. The role in infection and patterns of antimicrobial susceptibility for B. ureolyticus and B. gracilis were studied. Review of the clinical data indicated that 83% of B. gracilis strains were recovered from patients with serious visceral or head and neck infection, whereas 73% of B. ureolyticus isolates were recovered from superficial soft-tissue or bone infections. The strains of B. ureolyticus were uniformly susceptible to the tested antimicrobial agents. B. gracilis, however, showed some striking resistance, with penicillin active against only 67% and the cephalosporins active against 67 to 84% of the isolates tested. The association of B. gracilis with serious deep-tissue infection, coupled with the relatively high frequency of antibiotic resistance, indicates that it is an important, previously unrecognized, pathogen.

Anaerobic mediastinitis complicating median sternotomy

Two cases of mediastinitis and bacteremia caused by Bacteroides species following median sternotomy are described. In both patients, purulent sternal drainage and signs of systemic toxicity led to the diagnosis. Surgical reexploration and administration of appropriate antibiotics effected clinical cure. Although there is only a single previous case of anaerobic mediastinitis following median sternotomy incision reported, these two cases suggest that this unusual infection may not be so rare as previously thought.

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.

Isolation, characterization and ecological distribution of recently recognized propionic acid-negative Bacteroides species from human sources

140 strains of anaerobic, Gram-negative, propionate-negative, non-pigmented rods (Bacteroides oralis group) were isolated from normal flora and from clinical specimens. They were characterized by physiological tests, gas chromatography of the acid end products, and determination of the G + C content of their DNA. In addition, their distribution in the various biotopes of the human body (oropharyngeal tract, genitourinary tract, and gut) and in clinical specimens was investigated. The strains could be assigned to the recently described species Bacteroides denticola, B. buccae, B. buccalis, and B. oris, or to B. bivius, B. disiens and B. oralis. In the investigated group, especially B. bivius exhibits an antibiotic resistance--particularly against the beta-lactam antibiotics--comparable to that of B. fragilis.

In vitro activity of cefbuperazone compared with that of other new beta-lactam agents against anaerobic gram-negative bacilli and contribution of beta-lactamase to resistance

Cefbuperazone was compared with other currently available and investigational antibiotics against 278 clinical isolates of anaerobic gram-negative bacilli by an agar dilution method. Cefbuperazone and cefotetan were equally active against Bacteroides fragilis, with 8% of the organisms tested found to be resistant to 32 micrograms of either drug per ml. Cefoperazone, cefotaxime, ceftriaxone, and cefmetazole were less active against these strains; cefoxitin, moxalactam, piperacillin, clindamycin, and metronidazole were more active. None of the agents were consistently active against any of the other anaerobic gram-negative bacilli except imipenem, for which the minimum concentration required to inhibit 90% of all strains tested was 4 micrograms/ml. A 10,000-fold increase in inoculum size caused an increase in the MIC of ceftriaxone, cefotaxime, and cefoperazone but not of cefbuperazone, cefotetan, or cefoxitin. Investigation of the mechanism of resistance to cephalosporin-like agents demonstrated a correlation between the level of resistance and beta-lactamase activity. Cefbuperazone, cefotetan, and cefoxitin were not hydrolyzed, had lower MICs, and were less affected by changes in inoculum size than were cefotaxime, ceftriaxone, and cefoperazone.

Current trends in the diagnosis and treatment of tuboovarian abscess

Tuboovarian abscess is a well-recognized complication of acute salpingitis and has been reported in as many as one third of hospital admissions for acute salpingitis. The incidence of tuboovarian abscess is expected to increase as a result of the current epidemic of sexually transmitted diseases and their sequelae. Patients with tuboovarian abscess most commonly present with lower abdominal pain and an adnexal mass(es). Fever and leukocytosis may be absent. Ultrasound, computed tomographic scans, laparoscopy, or laparotomy may be necessary to confirm the diagnosis. Tuboovarian abscess may be unilateral or bilateral regardless of intrauterine contraceptive device usage. Tuboovarian abscess is polymicrobial with a preponderance of anaerobic organisms. An initial conservative antimicrobial approach to the management of the unruptured tuboovarian abscess is appropriate if the antimicrobial agents used can penetrate abscesses, remain active within the abscess environment, and are active against the major pathogens in tuboovarian abscess, including the resistant gram-negative anaerobes such as Bacteroides fragilis and Bacteroides bivius. However, if the patient does not begin to show a response within a reasonable amount of time, about 48 to 72 hours, surgical intervention should be undertaken. Suspicion of rupture should remain an indication for immediate operation. Once operation is undertaken, a conservative approach with unilateral adnexectomy for one-side tuboovarian abscess is appropriate if future fertility or hormone production is desired.

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.

Erythromycin: a microbial and clinical perspective after 30 years of clinical use (1)

Erythromycin is a macrolide that acts by inhibiting the translocation reaction during protein synthesis. Erythromycin is inactive against the Enterobacteriaceae and Pseudomonas aeruginosa except under alkaline conditions. Erythromycin is active against most gram-positive bacteria; some gram-negative bacteria, including Neisseria, Bordetella, Brucella, Campylobacter, and Legionella; and Treponema, Chlamydia, and Mycoplasma. The emergence of resistance to erythromycin is closely associated with its use and is often plasmid mediated. After its oral or parenteral administration, erythromycin diffuses readily into intracellular fluids and is actively concentrated intracellularly by polymorphonuclear leukocytes and alveolar macrophages.

Comparative in vitro activity of cefbuperazone against anaerobic bacteria isolated from community hospitals

The activity of cefbuperazone against 266 strains of anaerobic bacteria was determined by the agar dilution method and compared with cefoxitin, moxalactam, piperacillin, and clindamycin. All strains were recent clinical isolates from community hospitals. All agents tested showed good activity against Bacteroides fragilis, Fusobacterium spp., Propionibacterium spp., Clostridium septicum, Clostridium perfringens, and the anaerobic, gram-positive cocci and gram-negative cocci. Cefbuperazone, cefoxitin, and moxalactam had poor activity against Bacteroides thetaiotaomicron, Bacteroides ovatus, and Bacteroides distasonis. The susceptibility of other Clostridium spp., Lactobacillus spp., and Eubacterium lentum was variable. Our community hospital isolates showed a difference in susceptibility patterns from those reported from university and research centers. This supports the recommendation that clinical microbiology laboratories, including those in community hospitals, need to perform susceptibility testing on representative clinical isolates.

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%.

Antimicrobial susceptibilities of 1,292 isolates of the Bacteroides fragilis group in the United States: comparison of 1981 with 1982

A susceptibility survey of 537 strains of the Bacteroides fragilis group from eight centers in the United States was continued at the Tufts New England Medical Center in 1982. The results were compared with those of 755 organisms analyzed in 1981. Nine antimicrobial agents were tested by an agar dilution method. The respective percentages of resistance for 1981 and 1982 were as follows (%): cefoxitin, 8 and 10; moxalactam, 22 and 12; cefotaxime, 54 and 48; cefoperazone, 57 and 54; piperacillin, 12 and 7; clindamycin, 6 and 3; metronidazole, 0 and 0; chloramphenicol, 0 and 0; and tetracycline, 63 and 59. Regional differences in resistance rates were found. Declines in resistance to moxalactam, piperacillin, and clindamycin were noted at the participating hospitals. An outbreak of cefoxitin resistance was noted at the Tufts New England Medical Center, where the rate increased from 14 to 30%. The various species of the B. fragilis group had differing patterns of resistance; B. fragilis was the most susceptible species. Significant cross resistance among the beta-lactam agents was found. These data indicate the need to determine the susceptibility patterns of the B. fragilis group organisms within each hospital.

Effect of clavulanic acid on the activities of ten beta-lactam agents against members of the Bacteroides fragilis group

Clavulanic acid reduced the MICs of amoxicillin, carbencillin , cefamandole, cefotaxime, ceftazidime, ceftizoxime, cephalothin, and penicillin G, but not of cefoxitin or moxalactam, against 77 isolates of the Bacteroides fragilis group, all rapidly beta-lactamase positive by the nitrocefin slide test. It had no effect on the susceptibilities of eight Bacteroides distasonis strains that were slowly beta-lactamase positive (18 h of incubation).

Comparative in vitro activities of cefpiramide and apalcillin against anaerobic bacteria

The in vitro activities of two new antimicrobial agents, apalcillin and cefpiramide (SM-1652), were evaluated against 324 strains of anaerobic bacteria. Apalcillin (a penicillin derivative) and cefpiramide (a semisynthetic cephalosporin) were compared with piperacillin, moxalactam, and cefoxitin. Organisms studied included the Bacteroides fragilis group, other Bacteroides species, fusobacteria, clostridia, nonsporeforming gram-positive rods, and anaerobic cocci. Piperacillin was found to be the most active overall, inhibiting 96% of the strains tested at its achievable level in serum (128 micrograms/ml). Apalcillin was comparable in activity to piperacillin, inhibiting 93% of anaerobes tested at this concentration. The other antibiotics inhibited ca. 80% of the strains at 32 micrograms/ml. In terms of activities against particular species, apalcillin was active against 75% of B. fragilis group strains and 97 to 100% of all other anaerobes. Cefpiramide inhibited 37% of B. fragilis group strains at 32 micrograms/ml and 68% at 64 micrograms/ml (a level that may be achievable with this drug). Cefpiramide inhibited 92% of all other anaerobes at 32 micrograms/ml and 95% at 64 micrograms/ml. The clostridia other than Clostridium perfringens were the most resistant (84% inhibited at 32 micrograms/ml and 95% inhibited at 64 micrograms/ml).

Successful prophylaxis with tinidazole of infection after major head and neck surgery for malignant disease

A prospective double-blind trial of tinidazole was carried out in a group of 8 patients, each undergoing radical surgery for the removal of a large squamous cell carcinoma (SCC) of the oropharynx. In the 4 patients given tinidazole there was no wound infection, wound healing was more rapid and the foul odour associated with infection in such patients was eliminated. Post-operatively, 3 of the 4 patients given the placebo developed wound infections. Mixed cultures of gram-negative anaerobic bacilli, predominantly bacteroides, were grown from the upper drain fluids of the infected patients. Anaerobes were not isolated from the drain fluids of patients receiving tinidazole. The efficacy of tinidazole was demonstrated in these patients who are at high risk of acquiring infection because of the extensive surgery required for tumour removal and the inevitable contamination of the tissues with the diverse, resident oral flora.

Bacteremia due to Fusobacterium species

Twenty-six patients were identified as having bacteremia with Fusobacterium species over a five-year period at Boston City Hospital. They represented 0.9 percent of bacteremic patients and were equally divided as to sex. Bacteremia with Fusobacterium occurred primarily in young adults and in patients over 60 years of age and was not observed in children. In 16 patients (62 percent), Fusobacterium was the only blood culture isolate. The most common primary foci of infection were the female genital tract, the upper respiratory tract, the oral cavity, and the lower respiratory tract. Five patients had primary foci of infection that were initially occult. Three of these patients were found to have unappreciated oral and pharyngeal lesions, and one had a liver abscess; no primary infection was established in the remaining patient. Shock related to bacteremia developed in six patients (23 percent), four of whom had Fusobacterium species as the only blood culture isolate. Death occurred in three patients (12 percent), all of whom were over 60 years old. Metastatic infection occurred in only one patient in whom hematogenous osteomyelitis developed. Postpartum fusobacterial bacteremia was uniformly benign. Evaluation of bacteremia with Fusobacterium species in nonpostpartum patients, without an overt focus of infection, should be directed to a search for occult abscess, especially of the upper respiratory tract and oral cavity.

A comparison of four methods for detecting beta-lactamase in anaerobic bacteria

Four methods for detecting beta-lactamase activity in anaerobic bacteria were evaluated and compared to a nitrocefin saturated filter paper test. The methods studied were Cefinase, PADAC, Beta Lactam, and the slide iodometric technique. Fifty anaerobes were tested including species of Bacteroides, Fusobacterium, and Clostridium. The percentages of agreement with the nitrocefin test are: Cefinase 100%, PADAC 96%, slide iodometric 78%, and Beta Lactam 72%. Positive nitrocefin tests have been shown to correlate with a penicillin MIC greater than 0.78 micrograms/ml.

Susceptibility of the Bacteroides fragilis group in the United States in 1981

The minimal inhibitory concentrations of nine antimicrobial agents was determined for over 750 clinical isolates of the Bacteroides fragilis group of anaerobic bacteria collected from nine centers in the United States during 1981. High resistance rates were documented for cefoperazone, cefotaxime, and tetracycline. Cefoxitin had the best activity of the beta-lactam antibiotics, whereas moxalactam and piperacillin had good activities. The resistance rate for clindamycin was 6%. There were no metronidazole- or chloramphenicol-resistant isolates encountered. There were significant differences in susceptibility among the various species of the B. fragilis group, particularly with moxalactam, cefoxitin, and clindamycin. Clustering of clindamycin-, piperacillin-, and cefoxitin-resistant isolates was observed at different hospitals. The variability of resistance rates with the beta-lactam antibiotics and clindamycin indicates that susceptibility testing of significant clinical isolates should be performed to define local resistance patterns.

Comparative in vitro susceptibilities of anaerobic bacteria to cefmenoxime, cefotetan, and N-formimidoyl thienamycin

The in vitro activities of cefmenoxime, cefotetan, and N-formimidoyl thienamycin were compared with those of other antimicrobial agents (metronidazole, clindamycin, cefoxitin, and moxalactam) against anaerobic bacteria. The data obtained indicate that N-formimidoyl thienamycin exhibits excellent activity against anaerobic bacteria; cefotetan and cefmenoxime, though less active, should be of value in treating selected anaerobic infections.

Susceptibility testing of anaerobic bacteria

With the significant increase in resistance of anaerobic bacteria to antimicrobial agents in recent years, susceptibility testing of these organisms becomes very important. In addition to survey studies, hospitals should be determining their local patterns, and therapy of at least the more serious infections should be guided by susceptibility tests. Of the various tests available, those most suitable for smaller hospitals for guidance of patient management are the broth disc elution procedure and the micro broth dilution tray test.

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).

Comparative in vitro activity of ceftriaxone against anaerobic bacteria

The in vitro activity of ceftriaxone was compared with those of other recently introduced beta-lactam antimicrobial agents (cefoperazone, cefotaxime, and moxalactam) and with those of cefoxitin, clindamycin, and metronidazole against 227 strains of anaerobic bacteria. The data obtained in this investigation suggest that ceftriaxone, like a majority of the new beta-lactam antimicrobial agents, may be of limited value in the treatment of serious infections involving anaerobic bacteria.