title: beta-Lactamase production and susceptibility of US and European anaerobic gram-negative bacilli to beta-lactams and other agents.
abstract: 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.
authors.affiliation: Institute of Pathology, Case Western Reserve University, Cleveland, Ohio.
authors.forename: M R
authors.initials: MR
authors.lastname: Jacobs
authors.forename: S K
authors.initials: SK
authors.lastname: Spangler
authors.forename: P C
authors.initials: PC
authors.lastname: Appelbaum
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001438:Bacteroidaceae / Q000187:drug effects* / Q000201:enzymology; D001439:Bacteroides / Q000187:drug effects; D004357:Drug Synergism; D005673:Fusobacterium / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D001618:beta-Lactamases / Q000096:biosynthesis*; D047090:beta-Lactams
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases