The global consequence of disruption of the AcrAB-TolC efflux pump in Salmonella enterica includes reduced expression of SPI-1 and other attributes required to infect the host.
The mechanisms by which RND pumps contribute to pathogenicity are currently not understood. Using the AcrAB-TolC system as a paradigm multidrug-resistant efflux pump and Salmonella enterica serovar Typhimurium as a model pathogen, we have demonstrated that AcrA, AcrB, and TolC are each required for efficient adhesion to and invasion of epithelial cells and macrophages by Salmonella in vitro. In addition, AcrB and TolC are necessary for Salmonella to colonize poultry. Mutants lacking acrA, acrB, or tolC showed differential expression of major operons and proteins involved in pathogenesis. These included chemotaxis and motility genes, including cheWY and flgLMK and 14 Salmonella pathogenicity island (SPI)-1-encoded type III secretion system genes, including sopE, and associated effector proteins. Reverse transcription-PCR confirmed these data for identical mutants in two other S. Typhimurium backgrounds. Western blotting showed reduced production of SipA, SipB, and SipC. The absence of AcrB or TolC also caused widespread repression of chemotaxis and motility genes in these mutants, and for acrB::aph, this was associated with decreased motility. For mutants lacking a functional acrA or acrB gene, the nap and nir operons were repressed, and both mutants grew poorly in anaerobic conditions. All phenotypes were restored to that of the wild type by trans-complementation with the wild-type allele of the respective inactivated gene. These data explain how mutants lacking a component of AcrAB-TolC are attenuated and that this phenotype is a result of decreased expression of numerous genes encoding proteins involved in pathogenicity. The link between antibiotic resistance and pathogenicity establishes the AcrAB-TolC system as fundamental to the biology of Salmonella.
Webber
Mark A
MA
Antimicrobial Agents Research Group, Division of Immunity and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom.
Bailey
Andrew M
AM
Blair
Jessica M A
JM
Morgan
Eirwen
E
Stevens
Mark P
MP
Hinton
Jay C D
JC
Ivens
Al
A
Wain
John
J
Piddock
Laura J V
LJ
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D005816:Genetic Complementation Test; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics; D009154:Mutation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019779:Salmonella enterica / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D015534:Trans-Activators; C493251:AcrAB-TolC protein, Salmonella enterica; C531999:RamA protein, Salmonella typhimurium; C094578:Salmonella invasion protein C; C118287:SipA protein, Salmonella; C419942:Spi1 protein, Salmonella; C094579:invasion protein B, Salmonella typhimurium; C071266:FlgM protein, Bacteria