MRSA is typically spread by direct physical contact and indirect contact through objects such as towels, sheets, clothes, and sports equipment. Jails tend to be high-risk areas for MRSA due to the close living conditions and high turnover rates. In contrast to prisons where inmates serve longer sentences, jails are locally maintained facilities where the average sentence is one year or less. This population flux increases the chances of MRSA being commuted into the jail or out to the community.
This study, the first longitudinal study of MRSA in a jail setting, investigates the changing epidemiology of the bacteria over six years. The authors found that while there were six major S. aureus clonal groups present in their strain collection, two dominated: ST30:Z and ST8:S. Author Dr. Francoise Perdreau-Remington of the University of California, San Francisco notes, "The 1999 [ST30: Z] clone had only been previously described in Australia and New Zealand." The strain settled in California in 1996 and became the predominant clone until 2000, but was overtaken by ST8:S in 2001.
Doctors first identified the ST8:S clone in a sample collected from an outpatient in 2000. It appeared in the inpatient ward nine months later, and in that short time gained further multi-drug resistance. Perdreau-Remington states, "When we first saw the ST8:S clone in that one patient, it was 'only' erythromycin and methicillin resistant. Now it has acquired resistance to quinolones and, in some cases, to tetracycline."