A Bacteroides tetracycline resistance gene represents a new class of ribosome protection tetracycline resistance

Abstract

The ribosome protection type of tetracycline resistance (Tcr) has been found in a variety of bacterial species, but the only two classes described previously, Tet(M) and Tet(O), shared a high degree of amino acid sequence identity (greater than 75%). Thus, it appeared that this type of resistance emerged recently in evolution and spread among different species of bacteria by horizontal transmission. We obtained the DNA sequence of a Tcr gene from Bacteroides, a genus of gram-negative, obligately anaerobic bacteria that is phylogenetically distant from the diverse species in which tet(M) and tet(O) have been found. The Bacteroides Tcr gene defines a new class of ribosome protection resistance genes, Tet(Q), and has a deduced amino acid sequence that was only 40% identical to Tet(M) or Tet(O). Like tet(M) and tet(O), tet(Q) appears to have spread by horizontal transmission, but only within the Bacteroides group.

Presence of the Listeria tetracycline resistance gene tet(S) in Enterococcus faecalis

“…The DNA fragments to be used as probes for hybridization experiments were the 870-bp HincIl fragment of pT181 for tet(K) (15), the 310-bp ClaI-HpaII fragment of pBC16 for tet(L) (13), the 850-bp ClaI-HindIII fragment of TnJS45 for tet(M) (18), the 1,458-bp HindIII-NdeI fragment of pIP1433 for tet(O) (32), the 900-bp SphI-EcoRI fragment of pCW3 for tetA(P) (31), the 1,100-bp PstI-EcoRI fragment of pCW3 for tetB(P) (31), the 900-bp EcoRI-EcoRV fragment of pNFD13-2 for tet(Q) (20), the 590-bp fragment of pIP811 for tet(S) (5), and the 830-bp TaqI fragment of Tn1545 for int-Tn (23). Restriction endonuclease-generated fragments were separated by electrophoresis in 0.8% low-melting-temperature agarose type VII (Sigma Chemical Co., St. Louis, Mo.)…”

“…The first group mediates energy-dependent efflux of tetracycline from the cells and includes 10 classes of genes: tet(A) to tet(E) (33), tet(K) (15), tet(G) (36), tet(H) (12), tet(L) (13), and tet(P) (31). The second mechanism confers tetracycline and minocycline resistance by ribosomal protection and comprises four gene classes: tet(M) (18), tet(O) (32), tet(Q) (20), and tet(S) (5). Recently, a third mechanism, chemical modification of tetracycline, has been discovered in the genus Bacteroides and the resistance gene has been designated tet(X) (33).…”

Sequencing of a tet(Q) gene isolated from Bacteroides fragilis 1126

“…The tetA(Q)2 gene originated from Bacteroides fragilis 1126, a clinical strain isolated between 1978 and 1981 at University Hospital, San Diego, Calif., and identified by standard culture and biochemical methods (11). The tetA(Q)2 gene has been localized on a large transfer element and is linked to a clindamycin resistance locus whose self-transfer is regulated by exposure to tetracycline or clindamycin (13), as has also been reported for tet4(Q)1 (27). B. fragilis tetracycline resistance gene tetA(Q)2 was first identified on a 13-kb DNA fragment, subsequently mapped to a 2.8-kb region, and subcloned into the SmaI-ClaI sites of plasmid Bluescript II SK+, producing plasmid pBSK1.…”

“…Resistance to tetracycline is widespread among Bacteroides clinical isolates. In many colonic Bacteroides isolates, a nonplasmid conjugation system that mediates transfer of tetracycline resistance is induced by low levels of tetracycline (27,28). We report herein the sequence of a second tet(Q) gene isolated from a member of this genus and the comparison of this gene to that first reported by Nikolich et al (27).…”

“…Only one gene of the newly reported ribosomal protection determinant Tet Q has been described. This gene was isolated from Bacteroides thetaiotaomicron DOT (27) and is suggested to have spread horizontally among Bacteroides species (27).…”