Lytic activity of a new cephalosporin, cefuroxime, against gram-negative bacteria

Cefuroxime, a new cephalosporin antibiotic, was inhibitory at low concentrations to several types of gram-negative bacteria. It was considerably more stable than cephaloridine or cephalothin to the beta-lactamases produced by Escherichia coli (RP1), Klebsiella aerogenes K1 and Enterobacter cloacae P99. Concentrations of cefuroxime much greater than the minimum inhibitory concentration (MIC) were usually necessary to induce lysis of beta-lactamase and non-beta-lactamase producers. In contrast, cephaloridine, cephalothin and ampicillin were rapidly bacteriolytic at, or near, the respective MIC against non-beta-lactamase producers, whereas the activity of these three antibiotics was considerably reduced against beta-lactamase-producing strains.