Submitted to: Conference on Gastrointestinal Function
Publication Type: Abstract only
Publication Acceptance Date: 3/12/2003
Publication Date: 3/12/2003
Citation: Ziemer, C.J., Dang, E. 2003. Presence and expression of tetracycline genes in salmonella. Conference on Gastrointestinal Function. p. 54. Interpretive Summary:
Technical Abstract: Mobility of antibiotic resistance genes is accepted; however, whether acquisition of these genes modifies expression of other genes is not clear. Modification of gene expression may contribute to differences among serovars of food borne pathogens. An initial investigation to determined tetracycline resistance and presence of common resistance genes in Salmonella was conducted. Salmonella strains screened were obtained from the Salmonella Genetic Stock Center (Alberta, Canada) and included 46 strains (27 serovars) of Salmonella enterica subspecies I and 2 strains each from S. enterica subspecies II, subspecies IIIa and IIIb, subspecies IV, subspecies VI, subspecies VII and S. bongori. Expression of tetracycline resistance was determined aerobically by plating on Muller-Hinton agar and anaerobically on Wilkens-Chalgren agar containing 0, 4, 6, 8, 10, 12, 16 or 64 µg/ml chlortetracycline. Aerobically, 3 Salmonella strains were sensitive (¿ 4 µg/ml), 51 had intermediate resistance (6 to 12 µg/ml) and 6 were resistant to tetracycline (16 and 64 µg/ml). Expression of resistance was different in some strains when grown anaerobically; 14 sensitive, 34 intermediate and 12 resistant strains. Presence of tetracycline resistance genes (TRG) was determined by PCR for TRG efflux classes tet(A)-(E), (G), (H), (K) and (L) and ribosomal protection protein classes tet(M), (O), (Q), (S) and (W). TRG present were tet(C), tet(D), tet(A), tet(K), tet(H), tet(G), tet(L) and tet(B), in order of predominance. No tet(E) or ribosomal protection protein genes were detected in any strain. Multiple tetracycline resistance genes were detected in thirty one strains: 19 strains had 2 genes, 11 strains had 3 genes and one strain had 5 genes. In 3 of the resistant Salmonella, none of the TRG screened were present. The 3 tetracycline-sensitive strains were positive for resistance genes. The Salmonella studied appear to have a broader range of tetracycline resistance genes than other reports.