Overexpression of marA, soxS and acrB in veterinary isolates of Salmonella enterica rarely correlates with cyclohexane tolerance.
OBJECTIVE
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.
Antimicrobial Agents Research Group, Division of Immunity and Infection, University of Birmingham, UK.
Mark
M
Webber
Anthony M
AM
Buckley
Luke P
LP
Randall
Martin J
MJ
Woodward
Laura J V
LJ
Piddock
D000818:Animals; D000829:Animals, Domestic / Q000382:microbiology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003510:Cyclohexanes / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D024901:Drug Resistance, Multiple, Bacterial; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D008826:Microbial Sensitivity Tests; D019779:Salmonella enterica / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D012997:Solvents / Q000494:pharmacology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
C474926:AcrB protein, Salmonella enterica; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003510:Cyclohexanes; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C080002:MarA protein, E coli; D026901:Membrane Transport Proteins; D012997:Solvents; C485381:SoxS protein, Salmonella enterica; D015534:Trans-Activators