NEW TETRACYCLINE RESISTANCE DETERMINANTS CODING FOR RIBOSOMAL PROTECTION IN STREPTOCOCCI AND NUCLEOTIDE-SEQUENCE OF TET(T) ISOLATED FROM STREPTOCOCCUS-PYOGENES A498

An approach based on PCR has been developed to identify new members of the rer gene family in streptococci resistant to tetracycline and min ocycline. Degenerate primers, corresponding to portions of the conserv ed domains of the proteins Tet(M)? Tet(O), TetB(P), Tet(Q), and Tet(S) , all specifying tile tetracycline-minocycline resistance phenotype, w ere used to selectively amplify DNA fragments within the coding sequen ces, Nine streptococcal strains which do not carry the genes tet(hl), ret(O), tetB(P), tet(Q), or tet(S) mere investigated, Four of them gav e no detectable PCR products, The five remaining strains each yielded a PCR product of 1.1 kbp, DNA hybridization experiments showed that th ese putative Tet determinants fell into four new hybridization classes , of which one, Tet T, was further analyzed, The gene rct(T) was isola ted from Streptococcus pyogenes A498, and the nucleotide sequence that was necessary and sufficient for the expression of tetracycline resis tance in Escherichia coli was determined, The deduced Tet(T) protein c onsists of 651 amino acids, The protein most closely related to Tet(T) was Tet(Q), which has 49% identical amino acid residues, A phylogenet ic analysis revealed that Tet T represents a novel branching order amo ng the Tet determinants so far described.