Comparative activities of cefotaxime, a new cephalosporin derivative, and of selected beta-lactam antibiotics against Haemophilus species.

The activity of cefotaxime (HR756), a new semi-synthetic cephalosporin, was compared with the activity of ampicillin, carbenicillin, cephalothin, cephaloridine, cefazolin, cefamandole and cefoxitin against 247 strains of Haemophilus sp.; 20 of these strains produce a beta-lactam inactivating enzyme. The minimal inhibitoring concentrations were determined by the agar plate dilution technique. Cefotaxime is not only more active than any other cephalosporin but also than ampicillin, generally estimated the most active drug against Haemophilus sp. Bacteriostatic concentrations of cefotaxime which inhibit 50 and 95% of the strains (BSC50 and BSC95) were 0,009 microgram/ml and 0,03 microgram/ml, respectively, showing an activity 20 times superior to that of ampicillin. Cefotaxime activity was unaffected by the production of beta-lactamase.