[Pathways of enzymatic inactivation of levomycetin in El Tor vibrios with plasmid and chromosome resistance to the antibiotic].

Two possible mechanisms of enzymatic inactivation of levomycetin, i.e. acetylation of OH-groups and reduction of the n-nitrophenylic component by the cells and cell-free extracts of V. eltor 2044 with the plasmid or chromosome types of antibiotic resistance were studied in vitro. The vibrio containing the extrachromosome determinants were resistant to a number of antibiotics. The rate of levomycetin acetylation by them under conditions of intensive aeration and reduction of the antibiotic aromatic nitrogroup in the absence of oxygen was high. The cells with the chromosome resistance had a trace activity of levomycetin acetyltransferase. Still, they rather rapidly reduced levomycetin into its aminoderivative (during 2-hour incubation in the atmosphere of nitrogen 70-80% of the substrate are transformed into its summary arylamine). The antibiotic sensitive vibrio practically had no capacity for acetylation of levomycetin but could transform it into the reduced aminoderivative though to a less extent than the antibiotic resistant cells.