Conjugative transfer of tetracycline resistance in rumen streptococcal strains

In 11% of tested Streptococcus bovis strains a conjugative transfer of tetracycline resistance was observed when mating experiments were carried out on membrane filters. The recipient strain used was S. bovis BM114 with chromosomal resistance to rifampicin. In addition, in two strains tetracycline resistance was transferred also to recipient strain Enterococcus faecium AL6. The transfer frequencies were in the range of 10(-6) to 10(-3). The donor strains were screened for the presence of plasmids and one up to four bands of plasmid DNA in all tested strains were revealed. In spite of that isolation of plasmid DNA was successful only in 53/4/114 transconjugants. Transconjugant 32/114 contained amylase activity which was higher than in the donor strain.