PRESENCE OF THE LISTERIA TETRACYCLINE RESISTANCE GENE TET(S) IN ENTEROCOCCUS-FAECALIS

Two hundred thirty-eight tetracycline- and minocycline-resistant clini cal isolates of Enterococcus and Streptococcus spp. were investigated by dot blot hybridization for the presence of nucleotide sequences rel ated to tet(S) (first detected in Listeria monocytogenes BM4210), tet( K), tet(L), tet(M), tet(O), tet(P), and tet(Q) genes. The tet(S) deter minant was found in 22 strains of Enterococcus faecalis, associated wi th tet(M) in 9 of these isolates and further associated with tet(L) in 3 of these strains. tet(M) was detected in all strains of Streptococc us spp. and in all but 10 isolates of Enterococcus spp.; fet(L) was fo und in 93 enterococci and fet(O) was found in single isolates of E. fa ecalis and Streptococcus milleri. No hybridization with the tet(K), te t(P), and tet(Q) probes was observed. Transfer of tet(S) by conjugatio n to E. faecalis or to E. faecalis and L. monocytogenes was obtained f rom 8 of the 10 E. faecalis strains harboring only this tet gene. Hybr idization experiments with DNAs of four donors and of the correspondin g transconjugants suggested that tet(S) was located in the chromosome. These results indicate that the genetic support of fet(S) in E. faeca lis is different from that in L. monocytogenes, where it is carried by self-transferable plasmids, and confirm the notion of exchange of gen etic information between Enterococcus and Listeria spp. in nature.