Comparison of the In Vitro Activity of Several Cephalosporin Antibiotics Against Gram-Negative and Gram-Positive Bacteria Resistant to Cephaloridine

Abstract

The in vitro activity of each oftwo oral [cefatrizine , cephalexin] and three parenteral (cefamandole, cefazolin, cephapirin) cephalosporin antibiotics was compared with that of cephalothin against 168 clinical isolates of gramnegative and gram-positive bacteria selected as resistant to 20 ,g of cephaloridine per ml on the basis of agar dilution susceptibility test data. Each of the five other cephalosporins inhibited a greater percentage of gram-negative bacillary isolates than did cephalothin or cephaloridine, with minimal inhibitory concentration values ranging 2-to 50-fold lower. Significant differences between minimal inhibitory concentrations of the compounds tested were also observed in tests against strains of Streptococcus faecalis and of methicillin-resistant Staphylococcus aureus. Potential advantages of including more than a single cephalosporin antibiotic in the panel ofantibiotics used for routine susceptibility testing, suggested by these observations, are discussed.