Association of Environmental Contamination in the Home With the Risk for Recurrent Community-Associated, Methicillin-Resistant Staphylococcus aureus Infection

Abstract

Importance: The role of environmental contamination in recurrent Staphylococcus aureus infections within households and its potential effect on intervention strategies has been debated recently.

Objective: To assess whether household environmental contamination increases the risk for recurrent infection among individuals with a community-associated methicillin-resistant S aureus (MRSA) infection.

Design, setting, and participants: This cohort study was conducted from November 1, 2011, to June 30, 2014, in the Columbia University Medical Center catchment area. All patients within 72 hours of presentation with skin or soft-tissue infections and blood, urine, or sputum cultures positive for MRSA were identified. Two hundred sixty-two patients met study inclusion criteria; 83 of these (31.7%) agreed to participate (index patients) with 214 household members. Participants were followed up for 6 months, and 62 of the 83 households (74.7%) completed follow-up. Participants and researchers were blinded to exposure status throughout the study. Follow-up was completed on June 30, 2014, and data were assessed from July 1, 2014, to February 19, 2016.

Exposure: Concordant environmental contamination, defined as having an isolate with the identical staphylococcal protein A and staphylococcal chromosomal cassette mec type or antibiogram type as the index patient's clinical isolate, present on 1 or more environmental surfaces at the time of a home visit to the index patient after infection.

Main outcomes and measures: Index recurrent infection, defined as any self-reported infection among the index patients during follow-up.

Results: One patient did not complete any follow-up. Of the remaining 82 index patients, 53 (64.6%) were female and 59 (72.0%) were Hispanic. The mean age was 30 (SD, 20; range, 1-79) years. Forty-nine of 61 MRSA infections where the clinical isolate could be obtained (80.3%) were due to the epidemic strain USA300. Among the 82 households in which a patient had an index MRSA infection, the clinical isolate was present in the environment in 20 (24.4%) and not found in 62 (75.6%). Thirty-five patients (42.7%) reported a recurrent infection during follow-up, of whom 15 (42.9%) required hospitalization. Thirteen recurrent infections were from the 20 households (65.0%) with and 22 were from the 62 households (35.5%) without environmental contamination (P = .04). Environmental contamination increased the rate of index recurrent infection (incident rate ratio, 2.05; 95% CI, 1.03-4.10; P = .04).

Conclusions and relevance: Household environmental contamination was associated with an increased rate of recurrent infection. Environmental decontamination should be considered as a strategy to prevent future MRSA infections, particularly among households where an infection has occurred.

Figure 1

Flow chart of enrollment of individuals with CA-MRSA infections and their households in Northern Manhattan.

Figure 2

Distribution of spa types of 61 clinical isolates available for spa typing among infected individuals (index cases), colonized index cases, households with a colonized non-index household member, and environmentally contaminated households.

Figure 3

Kaplan-Meier survival curves showing rates of recurrent infection among indexes in households with concordant environmental contamination compared to indexes in households without concordant environmental contamination.