[Molecular-genetic structure and incompatibility of the nonconjugative enterobacterial R plasmids pKMR281 and pKMR285].

Physical maps of Enterobacteriaceae nonconjugative plasmids pKMR281 (Sm, Su, molecular weight of 6 kb) and pKMR285 (Sm, Su Tc, molecular weight of 9 kb) were constructed for endonucleases EcoRI, PstI, EcoRV, SmaI, BglII, SalI and PvuII. The genes controlling production of aminoglycoside-3''-phosphotransferase and dihydropteroate synthetase of type II and the genetic tetracycline resistance determinant of class A were localized on the plasmids. Heteroduplex analysis of plasmids pKMR281 and pKMR285 showed that plasmid pKMR281 was completely homologous to plasmid pKMR285. The site of plasmid pKMR285 nonhomology with respect to plasmid pKMR281 corresponded to the area containing the tetracycline resistance determinant. Plasmids pKMR281 and pKMR285 were compatible with the tester plasmids of 25 incompatibility groups of Enterobacteriaceae and probably constitute a new incompatibility group. It was shown that pKMR281 and pKMR285 type plasmids were widely distributed in clinical strains of E. coli and Shigella spp. isolated in the Krasnodar Region.