LY164846 in vitro antimicrobial activity testing, including disk diffusion susceptibility tests using 30-microgram disks.

A new oral cephalosporin, LY164846 (Eli Lilly & Co., Indianapolis, Ind.), was found to have a unique antimicrobial spectrum confined to methicillin-susceptible Staphylococcus spp., streptococci (except Enterococcus spp.), Haemophilus influenzae, Branhamella catarrhalis, and some anaerobes. Cephalothin in vitro tests (30-microgram disks or dilution) can represent LY164846 for laboratory testing if comparable interpretive breakpoints are applied to strains within the spectrum of LY164846. Organisms not inhibited by LY164846 (MICs greater than or equal to 32 micrograms/ml) were members of the family Enterobacteriaceae, Pseudomonas spp., Acinetobacter spp., enterococci, and some strains of Staphylococcus haemolyticus and of the Bacteroides fragilis group.