Genomic Epidemiology of MRSA During Incarceration at a Large Inner-City Jail.

BACKGROUND Congregate settings, such as jails, may be a location where colonized detainees transmit MRSA. We examined MRSA acquisition during incarceration and characterized the genomic epidemiology of MRSA entering the jail and isolated during incarceration. METHODS Males incarcerated at the Cook County Jail were enrolled within 72 hours of intake and MRSA surveillance cultures collected. Detainees in jail at Day30 were re-cultured to determine MRSA acquisition. A survey was administered to identify acquisition predictors. Genomic sequencing of surveillance and clinical isolates was integrated with epidemiologic and jail location data to track MRSA transmission pathways. RESULTS 800 males were enrolled; 19% MRSA colonized at intake. Of 184 who reached Day30 visit, 12 acquired MRSA. Heroin use before entering (OR 3.67,p=0.05) and sharing personal items during incarceration (OR=4.92,p=.01) were predictors of acquisition. Sequenced clinical USA300 isolates (n=112) were more genetically similar than diverse intake USA300 strains (p<0.001), suggesting jail transmission. Four acquired colonization isolates were within 20 SNVs of other isolates; 4 were within 20SNVs of an intake isolate, 2 for an acquisition isolate, and 1 for a clinical isolate. Individuals with genetically similar isolates were more likely to have had overlapping stays in the same buildings. CONCLUSION There was a high MRSA burden entering jail. Genomic analysis of acquisition and clinical isolates suggests potential spread of incoming strains and networks of spread during incarceration, with spread often occurring among detainees housed in similar locations. Sharing personal items during incarceration is associated with MRSA acquisition and could be a focus for intervention.