title: Chlorhexidine and mupirocin susceptibilities of methicillin-resistant staphylococcus aureus from colonized nursing home residents.
abstract: Chlorhexidine and mupirocin are used in health care facilities to eradicate methicillin-resistant Staphylococcus aureus (MRSA) carriage. The objective of this study was to assess the frequency of chlorhexidine and mupirocin resistance in isolates from nares carriers in multiple nursing homes and to examine characteristics associated with resistance. Nasal swab samples were collected from approximately 100 new admissions and 100 current residents in 26 nursing homes in Orange County, CA, from October 2008 to May 2011. MRSA isolates were tested for susceptibility by using broth microdilution, disk diffusion, and Etest; for genetic relatedness using pulsed-field gel electrophoresis; and for qac gene carriage by PCR. Characteristics of the nursing homes and their residents were collected from the Medicare Minimum Data Set and Long-Term Care Focus. A total of 829 MRSA isolates were obtained from swabbing 3,806 residents in 26 nursing homes. All isolates had a chlorhexidine MIC of ≤4 μg/ml. Five (0.6%) isolates harbored the qacA and/or qacB gene loci. Mupirocin resistance was identified in 101 (12%) isolates, with 78 (9%) isolates exhibiting high-level mupirocin resistance (HLMR). HLMR rates per facility ranged from 0 to 31%. None of the isolates with HLMR displayed qacA or qacB, while two isolates carried qacA and exhibited low-level mupirocin resistance. Detection of HLMR was associated with having a multidrug-resistant MRSA isolate (odds ratio [OR], 2.69; P = 0.004), a history of MRSA (OR, 2.34; P < 0.001), and dependency in activities of daily living (OR, 1.25; P = 0.004). In some facilities, HLMR was found in nearly one-third of MRSA isolates. These findings may have implications for the increasingly widespread practice of MRSA decolonization using intranasal mupirocin.
authors.affiliation: Department of Pathology, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA. jennifer-kroeger@uiowa.edu
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: McDanel
authors.forename: Courtney R
authors.initials: CR
authors.lastname: Murphy
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Diekema
authors.forename: Victor
authors.initials: V
authors.lastname: Quan
authors.forename: Diane S
authors.initials: DS
authors.lastname: Kim
authors.forename: Ellena M
authors.initials: EM
authors.lastname: Peterson
authors.forename: Kaye D
authors.initials: KD
authors.lastname: Evans
authors.forename: Grace L
authors.initials: GL
authors.lastname: Tan
authors.forename: Mary K
authors.initials: MK
authors.lastname: Hayden
authors.forename: Susan S
authors.initials: SS
authors.lastname: Huang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D002353:Carrier State; D002710:Chlorhexidine / Q000494:pharmacology*; D004202:Disinfectants / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D008134:Long-Term Care; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D008826:Microbial Sensitivity Tests; D016712:Mupirocin / Q000494:pharmacology*; D009296:Nasal Cavity / Q000187:drug effects / Q000382:microbiology; D009735:Nursing Homes; D016133:Polymerase Chain Reaction; D013203:Staphylococcal Infections / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004202:Disinfectants; D026901:Membrane Transport Proteins; C099272:QacB protein, Staphylococcus aureus; C068498:qacA protein, Staphylococcus aureus; D016712:Mupirocin; D002710:Chlorhexidine