Concentrations below, at, or greater than the minimum inhibitory concentration (MIC) of cefoxitin and cephalothin induced lysis of exponentially growing cultures of β-lactamase-negative and -positive strains of Cefoxitin induced more rapid lysis than cephalothin or cefuroxime, and the time for lysis to be completed was shorter when cefoxitin was used. The rate of decrease in numbers of colony forming units confirmed that cefoxitin exerted a more rapid effect on the cells.