GENETIC ORGANIZATION AND DISTRIBUTION OF TETRACYCLINE RESISTANCE DETERMINANTS IN CLOSTRIDIUM-PERFRINGENS

The Tet P determinant from the conjugative Clostridium perfringens R p lasmid pCW3 encodes two functional overlapping tetracycline resistance genes, tetA(P) and tetB(P), The tetA(P) gene encodes a putative 46-kD a transmembrane protein which mediates active efflux of tetracycline f rom the cell, while tetB(P) encodes a putative 72,6-kDa protein which has significant similarity to Tet M-like tetracycline resistance prote ins (J. Sloan, L. hi. McMurry, D, Lyras, S., B, Levy, and J, I, Rood, Mel. Microbiol, 11:403-415, 1994). In the present study, hybridization and PCR analysis of 81 tetracycline-resistant isolates of C, perfring ens showed that they all carried the tetA(P) gene, Most of these isola tes (93%) carried a second tetracycline resistance gene, with 53% carr ying tetB(P) and 40% carrying a tet(M)-like gene. Despite the wide dis tribution of the tetB(P) and ret(M) genes, no isolate which carried bo th of these determinants was detected. In isolates that carried both t etA(P) and tetB(P) these genes overlapped, as in pCW3, Isolates carryi ng this combination of genes originated from diverse geographical loca tions and environmental sources, The single Clostridium paraputrificum isolate examined carried tetA(P), indicating that this gene is not co nfined to C, perfringens, However, neither tetA(P) nor tetB(P) was det ected in the nine Clostridium difficile isolates tested, Nucleotide se quence analysis of isolates lacking tetB(P) revealed that they contain ed the tetA408(P) gene, which lacked the codons for the 12 carboxy-ter minal amino acids of the TetA(P) protein.