The inactivation of gentamicin and netilmicin by carbenicillin: its effect on Serratia marcescens.

Ten clinical isolates of Serratia marcescens were tested on Mueller-Hinton agar containing gentamicin or netilmicin with carbenicillin. The isolates grew on plates where inactivation occurred, at higher antibiotic concentrations, but failed at lower concentrations. This growth response was individualistic and not closely related to the minimum inhibitory concentrations.