Exposure of Escherichia coli and Salmonella enterica serovar Typhimurium to triclosan induces a species-specific response, including drug detoxification.
OBJECTIVE
The use of triclosan within various environments has been linked to the development of multiple drug resistance (MDR) through the increased expression of efflux pumps such as AcrAB-TolC. In this work, we investigate the effect of triclosan exposure in order to ascertain the response of two species to the presence of this widely used biocide.


METHODS
The transcriptomes of Salmonella enterica serovar Typhimurium SL1344 and Escherichia coli K-12 MG1655 after exposure to the MIC of triclosan (0.12 mg/L) were determined in microarray experiments. Phenotypic validation of the transcriptomic data included RT-PCR, ability to form a biofilm and motility assays.


RESULTS
Despite important differences in the triclosan-dependent transcriptomes of the two species, increased expression of efflux pump component genes was seen in both. Increased expression of soxS was observed in Salmonella Typhimurium, however, within E. coli, decreased expression was seen. Expression of fabBAGI in Salmonella Typhimurium was decreased, whereas in E. coli expression of fabABFH was increased. Increased expression of ompR and genes within this regulon (e.g. ompC, csgD and ssrA) was seen in the transcriptome of Salmonella Typhimurium. An unexpected response of E. coli was the differential expression of genes within operons involved in iron homeostasis; these included fhu, fep and ent.


CONCLUSIONS
These data indicate that whilst a core response to triclosan exposure exists, the differential transcriptome of each species was different. This suggests that E. coli K-12 should not be considered the paradigm for the Enterobacteriaceae when exploring the effects of antimicrobial agents.
Bailey
Andrew M
AM
Antimicrobial Agents Research Group, School of Immunity and Infection, The Medical School, The University of Birmingham, Birmingham, UK.
Constantinidou
Chrystala
C
Ivens
Al
A
Garvey
Mark I
MI
Webber
Mark A
MA
Coldham
Nick
N
Hobman
Jon L
JL
Wain
John
J
Woodward
Martin J
MJ
Piddock
Laura J V
LJ
D018441:Biofilms / Q000187:drug effects / Q000254:growth & development; D001692:Biological Transport; D004202:Disinfectants / Q000494:pharmacology*; D048168:Escherichia coli K12 / Q000187:drug effects* / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects*; D020869:Gene Expression Profiling; D008124:Locomotion / Q000187:drug effects; D026901:Membrane Transport Proteins / Q000096:biosynthesis; D020411:Oligonucleotide Array Sequence Analysis; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000502:physiology; D014260:Triclosan / Q000494:pharmacology*
D004202:Disinfectants; D026901:Membrane Transport Proteins; D014260:Triclosan