[In vitro activity of the oxa-beta-lactam LY 127935 against Bacteroides fragilis and other anaerobic gram-negative rods (author's transl)].

The susceptibility of 115 Bacteroidaceae strains to LY 127935 was determined by broth dilution, agar dilution and agar diffusion tests. Simultaneously, the strains were tested for degradation of the oxa-beta-lactam. Only five strains (3 Bacteroides fragilis and 3 Bacteroides oralis/Bacteroides bivius) partially degraded LY 127935. No major discrepancies between the results of the agar dilution and broth dilution tests were observed. According to the results obtained by the agar dilution method, 50 strains of B. fragilus were inhibited by concentrations of less than or equal to 8 microgram oxa-beta-lactam per ml. Members of the Bacteroides melaninogenicus group of organisms had agar dilution MICs of less than or equal to 0.5 microgram LY 127935 per ml and Fusobacterium/Sphaerophorus species were inhibited by less than or equal to 64 microgram/ml. Strains of Bacteroides thetaiotaomicron, B. oralis/B. bivius and Bacteroides spp. were less susceptible. Due to the narrow range of MICs observed with B. fragilis strains, no regression line could be computed for the relationship between MIC and zone size.