Acquired tetracycline and/or macrolide-lincosamides-streptogramin resistance in anaerobes

In general bacterial antibiotic resistance is acquired on mobile elements such as plasmids, transposons and/or conjugative transposons. This is also true for many antibiotic resistant anaerobic species described in the literature. Of the 23 different tetracycline resistant efflux genes identified, tet(B), tet(K), tet(L), and tetA(P) have been found in anaerobic species and six of the ten tetracycline resistant genes coding for ribosomal protection proteins, tet(M), tet(O), tetB(P), tet(Q), tet(W), and tet(32), have been identified in anaerobes. There are now three enzymes which inactivate tetracycline, of which the tet(X) has been identified in Bacteroides though is not functional under anaerobic growth conditions. A similar situation exists with the genes conferring macrolide-lincosamide-streptogramin (MLS) resistance. Of the 26 rRNA methylase MLS resistant genes characterized, five genes; erm(B), erm(C), erm(F), erm(G), and erm(Q), have been identified in anaerobes. In contrast, no genes coding for MLS resistant efflux proteins or inactivating enzymes have been described in anaerobic species. This mini-review will summarize what is known about tetracycline and MLS resistance in genera with anaerobic species and the mobile elements associated with acquired tetracycline and/or MLS resistance genes.