title: Environmental contamination as a risk factor for intra-household Staphylococcus aureus transmission.
abstract: BACKGROUND
  The household is a recognized community reservoir for Staphylococcus aureus. This study investigated potential risk factors for intra-household S. aureus transmission, including the contribution of environmental contamination.
  
  
  METHODS
  We investigated intra-household S. aureus transmission using a sample of multiple member households from a community-based case-control study examining risk factors for CA-MRSA infection conducted in Northern Manhattan. During a home visit, index subjects completed a questionnaire. All consenting household members were swabbed, as were standardized environmental household items. Swabs were cultured for S. aureus. Positive isolates underwent further molecular characterization. Intra-household transmission was defined as having identical strains among two or more household members. Multiple logistic regression was used to identify independent risk factors for transmission.
  
  
  RESULTS
  We enrolled 291 households: 146 index cases, 145 index controls and 687 of their household contacts. The majority of indexes were Hispanic (85%), low income (74%), and female (67%), with a mean age of 31 (range 1-79). The average size of case and control households was 4 people. S. aureus colonized individuals in 62% of households and contaminated the environment in 54% of households. USA300 was the predominant clinical infection, colonizing and environmental strain. Eighty-one households had evidence of intra-household transmission: 55 (38%) case and 26 (18%) control households (P<.01). Environmental contamination with a colonizing or clinical infection strain (aOR: 5.4 [2.9-10.3] P<.01) and the presence of a child under 5 (aOR: 2.3 [1.2-4.5] P = .02) were independently associated with transmission. In separate multivariable models, environmental contamination was associated with transmission among case (aOR 3.3, p<.01) and control households (aOR 27.2, p<.01).
  
  
  CONCLUSIONS
  Environmental contamination with a colonizing or clinical infection strain was significantly and independently associated with transmission in a large community-based sample. Environmental contamination should be considered when treating S. aureus infections, particularly among households with multiple infected members.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Columbia University, College of Physicians & Surgeons, New York, New York, United States of America. jrk2115@columbia.edu
authors.forename: Justin
authors.initials: J
authors.lastname: Knox
authors.forename: Anne-Catrin
authors.initials: AC
authors.lastname: Uhlemann
authors.forename: Maureen
authors.initials: M
authors.lastname: Miller
authors.forename: Cory
authors.initials: C
authors.lastname: Hafer
authors.forename: Glenny
authors.initials: G
authors.lastname: Vasquez
authors.forename: Peter
authors.initials: P
authors.lastname: Vavagiakis
authors.forename: Qiuhu
authors.initials: Q
authors.lastname: Shi
authors.forename: Franklin D
authors.initials: FD
authors.lastname: Lowy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015169:Colony Count, Microbial; D003710:Demography; D004783:Environmental Microbiology; D004787:Environmental Pollution / Q000032:analysis*; D005191:Family Characteristics; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000382:microbiology* / Q000635:transmission*; D013211:Staphylococcus aureus / Q000302:isolation & purification / Q000502:physiology*; D055815:Young Adult