Characterization of a new class of tetracycline-resistance gene tet(S) in Listeria monocytogenes BM4210.

The nucleotide sequence of the tetracycline (Tc)-minocycline (Mc)-resistance determinant of plasmid pIP811 from Listeria monocytogenes BM4210 has been determined. The gene, designated tet(S), was identified by analysis of the start and stop codons as a coding sequence of 1923 bp, corresponding to a protein with a calculated M(r) of 72,912. The apparent 68-kDa size estimated by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis of the protein characterized in a cell-free coupled transcription-translation system was in good agreement with the calculated value. The tet(S) gene product exhibits 79 and 72% amino acid identity with Tet(M) from Streptococcus pneumoniae and Tet(O) from Campylobacter coli, respectively. The distribution of tet(S) in strains of Gram+ and Gram- genera resistant to Tc (TcR) and Mc (McR) was studied by hybridization under high stringency using a 590-bp intragenic probe. Homology with tet(S) was detected in two clinical isolates of L. monocytogenes isolated in different geographical areas.