[2 mechanisms of tetracycline resistance in bacteria].

Two mechanisms of resistance to chlortetracycline stipulated by retarded transport of the antibiotic or decreased sensitivity to it of the translation apparatus were studied using clinical bacterial strains and strains obtained under laboratory conditions. No strict proportion between the population resistance to the antibiotic and the level of a decrease in its absorption by the bacterial cells was observed in most of the clinical and laboratory strains of Staph. aureus. Apparently the resistance level observed in the bacteria cannot be entirely explained by the retarded transport of the antibiotic in these cases. Direct experiments showed that sensitivity to chlortetracycline in the protein-synthesizing apparatus of some resistant strains of Staph. aureus 209 was decreased 10 times. On the other hand correlation between the level of the decrease in the absorption of the antibiotic and the level of the bacteria resistance to it was observed in resistant strains of E. coli. The protein-synthesizing apparatus of the resistant strains in this case preserved its sensitivity to chlortetracycline. Sensitivity of the protein-synthesizing apparatus to the antibiotic did not change in the process of the resistance induction by incubation of the baceria in the presence of low concentrations of the antibiotic.