Overexpression of marA, soxS and acrB in veterinary isolates of Salmonella enterica rarely correlates with cyclohexane tolerance

Webber, M., Buckley, A. M., Randall, L. P., Woodward, M. J. and Piddock, L. J. V. (2006) Overexpression of marA, soxS and acrB in veterinary isolates of Salmonella enterica rarely correlates with cyclohexane tolerance. Journal of Antimicrobial Chemotherapy, 57 (4). pp. 673-679. ISSN 0305-7453 doi: 10.1093/jac/dkl025

Abstract/Summary

Objectives: To determine the contribution of the AcrAB efflux system to cyclohexane tolerance in Salmonella enterica. Methods: The expression of the efflux pump gene, acrB, and regulators marA and soxS from 46 isolates of S. enterica of 14 different serovars was determined by comparative RT-PCR and denaturing HPLC analysis. Results: Twenty-one of the 46 isolates were cyclohexane tolerant, a phenotype associated with multiple antibiotic resistance (MAR) and overexpression of efflux pumps. Of the cyclohexane-tolerant isolates 81% were MAR, whereas only 44% of the cyclohexane-susceptible isolates were MAR, confirming the association between cyclohexane tolerance and MAR. However, there was no correlation between cyclohexane tolerance or MAR and overexpression of acrB, soxS or marA. Conclusions: These data suggest that cyclohexane tolerance in S. enterica can be mediated by an acrB-independent mechanism.