1972 Volume 25 Issue 7 Pages 400-404
Cephacetrile, 7-cyanacetamido-cephalosporanic acid, is a new cephalosporin active against many gram-positive and gram-negative organisms. Staphylococcus aureus and Streptococcus pyogenes were inhibited by less than 1 μg/ml, but 25 μg/ml were needed to inhibit enterococci. The majority of Escherichia coli and Klebsiella strains and Proteus mirabilis strains were inhibited by 12.5μg/ml. Serratia, indole-positive Proteus, Pseudomonas and Enterobacter strains were resistant to more than 100 μg/ml. The in vitro activity of cephacetrile was influenced by inoculum size. Tube dilution and agar-plate dilution methods used to determine MIC differed by two to eight-fold. Cephacetrile was hydrolyzed by β-lactamases of intact E. coli, S. typhymurium, E. cloacae, P. morganit, Ps. aeruginosa strains. Hydrolysis of cephacetrile by purified β-lactamases showed that cephacetrile was not hydrolyzed as rapidly as cephalothin or cephaloridine.