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."
The expansion in resistance is troubling, and Perdreau-Remington and her colleagues are attempting to understand why certain clones are spreading so rapidly outside the hospital environment and what drives their resistance to numerous drugs. The ability to track the spread of individual strains is made possible by using techniques like Pulsed Field Gel Electrophoresis (PFGE) and Multilocus Sequence Typing (MLST). A factor in facilitating the investigation of a geographical pattern of infection is whether or not a physician has a specimen sent for culture and analyzed. In this case, the careful characterization of the strains isolated from clinical specimens in these jails seemed to have brought the majority of MRSA out of their cells and into the spotlight.
Founded in 1979, Clinical Infectious Diseases publishes clinical articles twice monthly in a variety of areas of infectious disease, and is one of the most highly regarded journals in this specialty. It is published under the auspices of the Infectious Diseases Society of America (IDSA).