DISTRIBUTION OF GENES CONFERRING COMBINED RESISTANCE TO TETRACYCLINE AND MINOCYCLINE AMONG GROUP-B STREPTOCOCCAL ISOLATES FROM HUMANS AND VARIOUS ANIMALS

Forty-nine tetracycline and minocycline resistant streptococci of sero logical group B isolated from humans, cattle, pigs and nutrias were in vestigated for the presence of genes conferring this combined resistan ce. Southern blot hybridization of EcoRI-digested chromosomal DNA of t he bacteria revealed for 39 of the cultures a hybridization signal wit h tet(M), for four of the cultures a hybridization signal with tet(O) and for none of the cultures a hybridization signal with the tet(Q) ge ne probe. The restriction endonuclease digested and blotted DNA of six tetracycline and minocycline resistant group B streptococci did not h ybridize with any of the available gene probes. The tet(M) gene probes recognized complementary sequences on EcoRI fragments of approximatel y 10.5 kb and 21.5 kb, the tet(O) gene probe hybridized with fragments of approximately 19 kb. The hybridization of the tet(M) gene probe in two different patterns appeared to be related to the origin of the cu ltures.