The effect of osmolality on the response of Escherichia coli and Proteus mirabilis to penicillins

Abstract

The response of broth cultures of Escherichia coli and Proteus mirabilis to ampicillin was continuously monitored turbidometrically. The rapid lytic response which follows a few minutes after addition of the antibiotic as well as the later slow lysis of spheroplasts could be manipulated by altering the osmolality of the medium. A higher osmolality was found to be necessary to protect Esch. coli than Pr. mirabilis and this explains the differential response of the 2 organisms that we have previously described.