Kinetics and mechanisms of drug action on microorganisms XXII: Effects of aminosidine with and without organism pretreatment with bacteriostatic agents.

Escherichia coli generation in the logarithmic growth phase was inhibited in peptone broth USP at pH 7.0 without kill below 3.0 mug/ml of aminosidine. Above this value, the logarithms of the number of viables of the drug-treated culture ultimately decreased linearly with time and the slopes of these plots were independent of concentration. A concentration-dependent lag in the time of attainment of the cidal action was observed, and the extent of this lag was related to the ease of emergence of resistant organisms. The minimal concentration for cidal action increased with increasing concentrations of nutrients and with decreasing pH. Pretreatment of the cultures with novobiocin and tetracycline lessened the minimum bactericidal concentration of aminosidine whereas chloramphenicol pretreatment increased it. Tetracycline pretreatment inhibited the emergence of aminosidine-resistant organisms.