title: The environment as an unrecognized reservoir for community-associated methicillin resistant Staphylococcus aureus USA300: a case-control study.
abstract: BACKGROUND
  Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are spreading, but the source of infections in non-epidemic settings remains poorly defined.
  
  
  METHODS
  We carried out a community-based, case-control study investigating socio-demographic risk factors and infectious reservoirs associated with MRSA infections. Case patients presented with CA-MRSA infections to a New York hospital. Age-matched controls without infections were randomly selected from the hospital's Dental Clinic patient population. During a home visit, case and control subjects completed a questionnaire, nasal swabs were collected from index respondents and household members and standardized environmental surfaces were swabbed. Genotyping was performed on S. aureus isolates.
  
  
  RESULTS
  We enrolled 95 case and 95 control subjects. Cases more frequently reported diabetes mellitus and a higher number of skin infections among household members. Among case households, 53 (56%) were environmentally contaminated with S. aureus, compared to 36 (38%) control households (p = .02). MRSA was detected on fomites in 30 (32%) case households and 5 (5%; p<.001) control households. More case patients, 20 (21%) were nasally colonized with MRSA than were control indexes, 2 (2%; p<.001). In a subgroup analysis, the clinical isolate (predominantly USA300), was more commonly detected on environmental surfaces in case households with recurrent MRSA infections (16/36, 44%) than those without (14/58, 24%, p = .04).
  
  
  CONCLUSIONS
  The higher frequency of environmental contamination of case households with S. aureus in general and MRSA in particular implicates this as a potential reservoir for recolonization and increased risk of infection. Environmental colonization may contribute to the community spread of epidemic strains such as USA300.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America. au2110@columbia.edu
authors.forename: Anne-Catrin
authors.initials: AC
authors.lastname: Uhlemann
authors.forename: Justin
authors.initials: J
authors.lastname: Knox
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: Megan
authors.initials: M
authors.lastname: Ryan
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; D017714:Community-Acquired Infections / Q000382:microbiology*; D004197:Disease Reservoirs / Q000382:microbiology*; D004781:Environmental Exposure; D004783:Environmental Microbiology; D005260:Female; D006794:Household Articles; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D008875:Middle Aged; D009666:Nose / Q000382:microbiology; D012008:Recurrence; D012307:Risk Factors; D055815:Young Adult