title: Prevalence of qacA/B Genes and Mupirocin Resistance Among Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates in the Setting of Chlorhexidine Bathing Without Mupirocin.
abstract: OBJECTIVE
  We aimed to determine the frequency of qacA/B chlorhexidine tolerance genes and high-level mupirocin resistance among MRSA isolates before and after the introduction of a chlorhexidine (CHG) daily bathing intervention in a surgical intensive care unit (SICU).
  
  
  METHODS
  Retrospective cohort study (2005-2012) SETTING: A large tertiary-care center
  
  
  METHODS
  Patients admitted to SICU who had MRSA surveillance cultures of the anterior nares
  
  
  METHODS
  A random sample of banked MRSA anterior nares isolates recovered during (2005) and after (2006-2012) implementation of a daily CHG bathing protocol was examined for qacA/B genes and high-level mupirocin resistance. Staphylococcal cassette chromosome mec (SCCmec) typing was also performed.
  
  
  RESULTS
  Of the 504 randomly selected isolates (63 per year), 36 (7.1%) were qacA/B positive (+) and 35 (6.9%) were mupirocin resistant. Of these, 184 (36.5%) isolates were SCCmec type IV. There was a significant trend for increasing qacA/B (P=.02; highest prevalence, 16.9% in 2009 and 2010) and SCCmec type IV (P<.001; highest prevalence, 52.4% in 2012) during the study period. qacA/B(+) MRSA isolates were more likely to be mupirocin resistant (9 of 36 [25%] qacA/B(+) vs 26 of 468 [5.6%] qacA/B(-); P=.003).
  
  
  CONCLUSIONS
  A long-term, daily CHG bathing protocol was associated with a change in the frequency of qacA/B genes in MRSA isolates recovered from the anterior nares over an 8-year period. This change in the frequency of qacA/B genes is most likely due to patients in those years being exposed in prior admissions. Future studies need to further evaluate the implications of universal CHG daily bathing on MRSA qacA/B genes among hospitalized patients.
authors.affiliation: 1Department of Medicine,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: David K
authors.initials: DK
authors.lastname: Warren
authors.affiliation: 1Department of Medicine,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Martin
authors.initials: M
authors.lastname: Prager
authors.affiliation: 1Department of Medicine,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Satish
authors.initials: S
authors.lastname: Munigala
authors.affiliation: 2Department of Pathology & Immunology,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Meghan A
authors.initials: MA
authors.lastname: Wallace
authors.affiliation: 2Department of Pathology & Immunology,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Colleen R
authors.initials: CR
authors.lastname: Kennedy
authors.affiliation: 1Department of Medicine,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Kerry M
authors.initials: KM
authors.lastname: Bommarito
authors.affiliation: 3Department of Surgery,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: John E
authors.initials: JE
authors.lastname: Mazuski
authors.affiliation: 2Department of Pathology & Immunology,Washington University School of Medicine,St. Louis,Missouri.
authors.forename: Carey-Ann D
authors.initials: CA
authors.lastname: Burnham
mesh_terms: D000328:Adult; D000368:Aged; D000891:Anti-Infective Agents, Local / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics*; D001494:Baths / Q000379:methods*; D002710:Chlorhexidine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008923:Missouri; D009296:Nasal Cavity / Q000382:microbiology; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000453:epidemiology*; D062606:Tertiary Care Centers
chemical_list: D000891:Anti-Infective Agents, Local; D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; C099272:QacB protein, Staphylococcus aureus; C068498:qacA protein, Staphylococcus aureus; D002710:Chlorhexidine
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