Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2002
Publication Date: May 20, 2002
Citation: Ziemer, C.J., Dang, E. 2002. Presence and expression of tetracycline resistance genes in salmonella. American Society for Microbiology. P. 515. 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 foodborne 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 and included 46 strains 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 by plating on Muller-Hinton agar containing 0, 4, 6, 8, 10, 12, 16 or 64 ug/ml chlortetracycline. Five Salmonella strains were sensitive to tetracycline, 38 had intermediate resistance, and 17 were resistant to tetracycline; 5 strains grew on 64 ug/ml tetracycline agar. Presence of tetracycline resistance genes (TRG) was determined by PCR for TRG classes (A)-(E), (G), and (L). TRG present were tet(C), tet(D), tet(A), tet(G), tet(L) and tet(B), in order of predominance. No tet(E) genes were detected in any strain. Multiple TRG were detected in 22 Salmonella, 5 with 3 genes and 17 with 2 genes; however, number of TRG present did not correlate with increased resistance. In 5 of the 17 resistant Salmonella, none of the TRG screened were present. Of the 5 tetracycline-sensitive strains, 3 were positive for resistance genes. The Salmonella studied appear to have a broader range of tetracycline resistance mechanisms than other reports.