[Mapping of the genetic locus determining the degree of natural resistance to erythromycin in Salmonella].

The locus which determines ordinary (natural--ery or) level of resistance to erythromycin in Salmonella has been mapped. According to the results of conjugation mating and the analysis of the properties' transfer gradient this region is localized next to his--locus, the gene order being; trp--his--eryor. However, no contransduction of eryor--locus with his--gene has been demonstrated. An assumption on a possible mechanism of alteration of natural level of erythromycin resistance in S. typhimurium mutants Er-4 and Es-1 (received earlier) has been made. This mechanism is connected with alterations in cell permeability.