Tetracycline resistance determinants among streptococci of serological group G and L

In the present study 56 streptococci of serological group G and L isolated from various animal species and from humans were investigated for tetracycline and minocycline resistance and for the presence of genes conferring this combined resistance. Among the 45 group G streptococci, 2 isolates from dogs, 3 from cattle and 2 from humans, respectively, as well as all 11 group L streptococci isolated from cattle, pigs or poultry were resistant to tetracycline and simultaneously to minocycline. The restriction endonuclease digested and blotted DNA-preparation of the tetracycline-and minocycline resistant group G streptococci from dogs and humans hybridized with the tet (M) gene probe, those from bovines with the tet (O) gene probe. Six group L streptococci carried the gene tet (M), whereas 5 isolates harboured the gene tet (O). The tet (M)-and tet (O) gene probes recognized complementary sequences on EcoRI-fragments of various sizes.