Comparison of in vitro activity of GR 20263, a novel cephalosporin derivative, with activities of other beta-lactam compounds.

The in vitro activity of GR 20263, a new cephalosporin, was compared primarily with the activities of moxalactam (LY 127935), cefotaxime, cefoxitin, cefuroxime, and cefazolin against 293 clinical isolates of a variety of gram-positive and -negative bacteria. The minimal inhibitory concentrations of GR 20263 for 90% of group isolates were between 0.06 and 0.5 microgram/ml for the Enterobacteriaceae, Haemophilus influenzae, Neisseria gonorrhoeae, and Lancefield group A beta-hemolytic streptococci; 2 micrograms/ml for Pseudomonas aeruginosa; 16 micrograms/ml for Staphylococcus aureus; and in excess of 128 micrograms/ml for Bacteroides fragilis and Lancefield group D streptococci. In comparison with the other agents, GR 20263 was markedly more active against the Enterobacteriaceae than cefuroxime, cefoxitin, and cefazolin, but marginally less active than moxalactam or cofotaxime. Aganist S. aureus, cefazolin was 16-fold and cefotaxime was 4-fold more active than GR 20263 and moxalactam. GR 20263 was eight-fold more active than cefotaxime and moxalactam against P. aeruginosa.