title: Chlorhexidine Induces VanA-Type Vancomycin Resistance Genes in Enterococci.
abstract: Chlorhexidine is a bisbiguanide antiseptic used for infection control. Vancomycin-resistantE. faecium(VREfm) is among the leading causes of hospital-acquired infections. VREfm may be exposed to chlorhexidine at supra- and subinhibitory concentrations as a result of chlorhexidine bathing and chlorhexidine-impregnated central venous catheter use. We used RNA sequencing to investigate how VREfm responds to chlorhexidine gluconate exposure. Among the 35 genes upregulated ≥10-fold after 15 min of exposure to the MIC of chlorhexidine gluconate were those encoding VanA-type vancomycin resistance (vanHAX) and those associated with reduced daptomycin susceptibility (liaXYZ). We confirmed thatvanAupregulation was not strain or species specific by querying other VanA-type VRE. VanB-type genes were not induced. ThevanHpromoter was found to be responsive to subinhibitory chlorhexidine gluconate in VREfm, as was production of the VanX protein. UsingvanHreporter experiments withBacillus subtilisand deletion analysis in VREfm, we found that this phenomenon is VanR dependent. Deletion ofvanRdid not result in increased chlorhexidine susceptibility, demonstrating thatvanHAXinduction is not protective against chlorhexidine. As expected, VanA-type VRE is more susceptible to ceftriaxone in the presence of sub-MIC chlorhexidine. Unexpectedly, VREfm is also more susceptible to vancomycin in the presence of subinhibitory chlorhexidine, suggesting that chlorhexidine-induced gene expression changes lead to additional alterations in cell wall synthesis. We conclude that chlorhexidine induces expression of VanA-type vancomycin resistance genes and genes associated with daptomycin nonsusceptibility. Overall, our results indicate that the impacts of subinhibitory chlorhexidine exposure on hospital-associated pathogens should be further investigated in laboratory studies.
authors.affiliation: Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA.
authors.forename: Pooja
authors.initials: P
authors.lastname: Bhardwaj
authors.affiliation: Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Ziegler
authors.affiliation: Department of Biological Sciences, University of Texas at Dallas, Richardson, Texas, USA kelli.palmer@utdallas.edu.
authors.forename: Kelli L
authors.identifier: http://orcid.org/0000-0002-7343-9271
authors.initials: KL
authors.lastname: Palmer
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D019729:Carbon-Oxygen Ligases / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000187:drug effects / Q000378:metabolism; D002710:Chlorhexidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017576:Daptomycin / Q000494:pharmacology; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D008826:Microbial Sensitivity Tests; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance / Q000187:drug effects* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D014157:Transcription Factors; C071437:VanA ligase, Bacteria; C073902:VanR protein, bacteria; D014640:Vancomycin; D019729:Carbon-Oxygen Ligases; C010882:chlorhexidine gluconate; D017576:Daptomycin; D002710:Chlorhexidine
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