Mode of antibacterial action of cefprozil, a new cephalosporin, on Escherichia coli, Serratia marcescens and Morganella morganii.

The mode of antibacterial action of cefprozil (CFPZ, BMY-28100), a newly developed cephalosporin, was investigated using Escherichia coli K12, Serratia marcescens IFO 12648 and Morganella morganii IFO 3848 as test organisms, in comparison with the action of cefaclor (CCL). The minimum inhibitory concentrations (MICs) of CFPZ for these organisms were 1.56, 800 and 25 micrograms/ml, whereas those of CCL were 1.56, 800 and 100 micrograms/ml, respectively. The addition of a subinhibitory concentration (1/4 MIC) of ethylenediaminetetraacetic acid (EDTA), which damages the permeability barrier of the outer membrane, markedly reduced the MICs of CFPZ for E. coli and S. marcescens, compared with those of CCL, whereas the MICs of both antibiotics for M. morganii were hardly affected by the presence of EDTA. CFPZ was more stable to beta-lactamase activities from these organisms than CCL. The cross-linking reactions of peptidoglycan synthesis catalyzed by the ether-treated cells from these organisms were inhibited by a lower concentration of CFPZ than of CCL.