Comparison of the In Vitro Activities of HR756 with Cephalothin, Cefoxitin, and Cefamandole

Abstract

The in vitro activity of HR756, a new semisynthetic cephalosporin, was compared with the activities of cephalothin, cefoxitin, and cefamandole against 1,535 isolates of gram-positive and gram-negative bacteria. HR756 was less active than cephalothin and cefamandole and twofold more active than cefoxitin against Staphylococcus . All four of the antibiotics were inactive against the enterococcus group of Streptococcus ; however, HR756 was the most active antibiotic against the other isolates of Streptococcus . HR756 was also more active against isolates of Enterobacteriaceae , including 84 to 95% of the isolates resistant to one or more of the other three antibiotics. HR756, at a concentration of 12.5 μg/ml, inhibited 86, 75, and 100% of the isolates of Pseudomonas aeruginosa , other Pseudomonas species, and Acinetobacter , respectively. The minimal inhibitory concentrations and minimal bactericidal concentrations of HR756 were within one twofold dilution for 11 of 21 gram-positive cocci and 119 of 125 gram-negative bacilli tested.