In vitro activity of cefotaxime against clinically significant pathogens

The present in vitro antibacterial activities of cefotaxime and 8 other cephalosporins (cefoperazone, cefmenoxime, cefpiramide, latamoxef, cefamandole, cefmetazole, cefotiam and cephazolin) were evaluated simultaneously in 384 strains of Gram-positive cocci, 595 strains of Enterobacteriaceae, 240 strains of non-fermenters and 143 strains of anaerobes and miscellaneous organisms. The results were expressed as minimum inhibitory concentration (MIC) range, MIC50 and MIC90. Of the beta-lactams, cefotaxime and latamoxef exhibited the highest activity against a wide variety of Gram-positive and Gram-negative bacteria. MIC90 of cefotaxime, however, for species of Pseudomonas aeruginosa, Xanthomonas maltophilia, enterococci, Bacteroides sp. and Clostridium difficile were more than 100 mg/L. Cefpiramide and cefoperazone were generally less active than these 2 agents. All strains were tested for beta-lactamase production by the cefinase disc method and the relationship of susceptibility to beta-lactams was evaluated in each species. The need was demonstrated for periodic susceptibility testing to be performed to better guide empirical antimicrobial therapy.