In vitro comparison of three new cephalosporins: LY-127935, cefotaxime and cefoperazone.

The comparative in vitro activity of three new cephalosporin antibiotics Ly-127935 (LY), cefotaxime (CTX) and cefoperazone (CFP) was examined. LY, CTX and CFP had similar activity against Staphylococcus aureus, Escherichia coli and Proteus mirabilis while CFP was less inhibitory than LY or CTX against Klebsiella spp.; indole + Proteus and gentamicin (GM)-susceptible Serratia. LY and CTX were effective while CFP was inactive against Enterobacter spp. and GM-resistant Serratia. CFP was more active than LY or CTX against GM-susceptible Pseudomonas aeruginosa but was the least active agent against GM-resistant isolates. Bacteroides fragilis were more susceptible to LY than CTX or CFP. Combination studies against P. aeruginosa with cephalosporin-GM pairs demonstrated synergy.