Contamination of environmental surfaces with Staphylococcus aureus in households with children infected with methicillin-resistant S aureus

Abstract

Importance: Household environmental surfaces may serve as vectors for the acquisition and spread of methicillin-resistant Staphylococcus aureus (MRSA) among household members, although few studies have evaluated which objects are important reservoirs of MRSA.

Objectives: To determine the prevalence of environmental MRSA contamination in households of children with MRSA infection; define the molecular epidemiology of environmental, pet, and human MRSA strains within households; and identify factors associated with household MRSA contamination.

Design, setting, and participants: Fifty children with active or recent culture-positive community-associated MRSA infection were enrolled from 2012 to 2013 at St Louis Children's Hospital and at community pediatric practices affiliated with the Washington University Pediatric and Adolescent Ambulatory Research Consortium in St Louis, Missouri.

Main outcomes and measures: Samples of participants' nares, axillae, and inguinal folds were cultured to detect S aureus colonization. Samples of 21 household environmental surfaces, as well as samples obtained from pet dogs and cats, were cultured. Molecular typing of S aureus strains was performed by repetitive-sequence polymerase chain reaction to determine strain relatedness within households.

Results: Methicillin-resistant S aureus was recovered from samples of environmental surfaces in 23 of the 50 households (46%), most frequently from the participant's bed linens (18%), television remote control (16%), and bathroom hand towel (15%). It colonized 12% of dogs and 7% of cats. At least 1 surface was contaminated with a strain type matching the participant's isolate in 20 households (40%). Participants colonized with S aureus had a higher mean (SD) proportion of MRSA-contaminated surfaces (0.15 [0.17]) than noncolonized participants (0.03 [0.06]; mean difference, 0.12 [95% CI, 0.05-0.20]). A greater number of individuals per 1000 ft 2 (93 m2) were also associated with a higher proportion of MRSA-contaminated surfaces (β = 0.34, P = .03). The frequency of cleaning household surfaces was not associated with S aureus environmental contamination.

Conclusions and relevance: Methicillin-resistant S aureus strains concordant with infecting and colonizing strains are present on commonly handled household surfaces, a factor that likely perpetuates MRSA transmission and recurrent disease. Future studies are needed to determine methods to eradicate environmental contamination and prevent MRSA transmission in households.

Figure 1. Proportion of households contaminated with an environmental strain type correlating with the participants’ baseline colonizing or infecting strain type by household surface

NOTE: RepPCR queries the entire chromosome but is not specific to the mecA gene; thus an MRSA and MSSA strain could be considered concordant by this typing method. N for each surface determined by whether the surface was available for sampling and if there was at least one baseline isolate for the participant (colonizing or infecting) available for analysis (nine participants had no baseline isolates available).