Comparative Activity of Cefotaxime and Selected f3-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 f3-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>90070 of the isolates of Pseudomonas aeruginosa at concentrations of ~16 tJg/ml; these drugs were, however, more active than carbenicillin. Among the (J-Iactam antibiotics, ampicillin ha