Comparative in vitro activities of third-generation cephalosporins

The in vitro susceptibilities of 823 clinical isolates to eight third-generation cephalosporin and cephalosporinlike antibiotics were studied. All eight antibiotics were more active and had broader spectrums of activity against gram-negative bacilli and anaerobes than older derivatives; however, they were less active against gram-positive cocci. Cefotaxime sodium, cefmenoxime hydrochloride, ceftriaxone disodium, and ceftizoxime sodium had similar activities. Cefoperazone sodium was more active than those drugs against Pseudomonas aeruginosa but less active against Enterobacteriaceae and Acinetobacter. Ceftazidime pentahydrate was more active against P aeruginosa but less active against gram-positive cocci. Moxalactam disodium was more active against some Enterobacteriaceae, Pseudomonas maltophilia, and Bacteroides fragilis but less active against gram-positive cocci. Thienamycin formamidide monohydrate had the broadest spectrum of activity and was the only antibiotic active against Streptococcus faecalis; the only resistant species were P maltophilia and Pseudomonas cepacia.