Comparative activity of cefotaxime and selected beta-lactam antibiotics against Haemophilus influenzae and aerobic gram-negative bacilli.

The activity of cefotaxime was compared with that of ampicillin, moxalactam, and cefoperozone against 50 isolates of Haemophilus influenzae and with that of ampicillin, carbenicillin, cephalothin, cefoxitin, cefamandole, cefazolin, and several other established and investigational beta-lactam antibiotics against several hundred isolates of gram-negative aerobic enteric bacilli. Minimal inhibitory concentrations of the drugs were determined by the agar plate dilution technique for H. influenzae and by the microtiter broth dilution technique for the other pathogens. Cefotaxime was the most active agent against H. influenzae; it was 20 times more active than ampicillin. It was also the most active agent against Escherichia coli, Klebsiella pneumoniae, nontyphoid Salmonella species, and Yersinia enterocolitica. Cefotaxime was among the most active agents against Enterobacter cloacae, Citrobacter species, Shigella species, Proteus mirabilis, and Acinetobacter calcoaceticus. None of the new cephalosporins or penicillin inhibited greater than 90% of the isolates of Pseudomonas aeruginosa at concentrations of less than or equal to 16 micrograms/ml; these drugs were, however, more active than carbenicillin.