title: A case control study of environmental and occupational exposures associated with methicillin resistant Staphylococcus aureus nasal carriage in patients admitted to a rural tertiary care hospital in a high density swine region.
abstract: BACKGROUND
  Distinct strains of methicillin resistant Staphylococcus aureus (MRSA) have been identified on livestock and livestock workers. Industrial food animal production may be an important environmental reservoir for human carriage of these pathogenic bacteria. The objective of this study was to investigate environmental and occupational exposures associated with nasal carriage of MRSA in patients hospitalized at Vidant Medical Center, a tertiary hospital serving a region with intensive livestock production in eastern North Carolina.
  
  
  METHODS
  MRSA nasal carriage was identified via nasal swabs collected within 24 hours of hospital admission. MRSA carriers (cases) were gender and age matched to non-carriers (controls). Participants were interviewed about recent environmental and occupational exposures. Home addresses were geocoded and publicly available data were used to estimate the density of swine in residential census block groups of residence. Conditional logistic regression models were used to derive odds ratio (OR) estimates and 95% confidence intervals (CI). Presence of the scn gene in MRSA isolates was assessed. In addition, multi locus sequence typing (MLST) of the MRSA isolates was performed, and the Diversilab® system was used to match the isolates to USA pulsed field gel electrophoresis types.
  
  
  RESULTS
  From July - December 2011, 117 cases and 119 controls were enrolled. A higher proportion of controls than cases were current workforce members (41.2% vs. 31.6%) Cases had a higher odds of living in census block groups with medium densities of swine (OR: 4.76, 95% CI: 1.36-16.69) and of reporting the ability to smell odor from a farm with animals when they were home (OR: 1.51, 95% CI: 0.80-2.86). Of 49 culture positive MRSA isolates, all were scn positive. Twenty-two isolates belonged to clonal complex 5.
  
  
  CONCLUSIONS
  Absence of livestock workers in this study precluded evaluation of occupational exposures. Higher odds of MRSA in medium swine density areas could reflect environmental exposure to swine or poultry.
authors: Department of Epidemiology, The University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. schinasi@email.unc.edu.
authors: Leah
authors: L
authors: Schinasi
authors: Steve
authors: S
authors: Wing
authors: Kerri L
authors: KL
authors: Augustino
authors: Keith M
authors: KM
authors: Ramsey
authors: Delores L
authors: DL
authors: Nobles
authors: David B
authors: DB
authors: Richardson
authors: Lance B
authors: LB
authors: Price
authors: Maliha
authors: M
authors: Aziz
authors: Pia D M
authors: PD
authors: MacDonald
authors: Jill R
authors: JR
authors: Stewart
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002353:Carrier State; D016022:Case-Control Studies; D004269:DNA, Bacterial / Q000032:analysis; D004781:Environmental Exposure; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006780:Hospitals, Rural / Q000706:statistics & numerical data; D006784:Hospitals, Teaching / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics / Q000302:isolation & purification*; D008875:Middle Aged; D009297:Nasal Mucosa / Q000382:microbiology*; D009657:North Carolina / Q000453:epidemiology; D011156:Population Density; D012111:Residence Characteristics; D013552:Swine; D062606:Tertiary Care Centers / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial