People who harbor methicillin-resistant Staphylococcus aureus (MRSA) for more than 1 year remain at substantial risk of MRSA-related illness or death, according to a single-center retrospective cohort study published in the July 15 issue of Clinical Infectious Diseases.
Patients with newly acquired MRSA are at significant risk for short-term morbidity and mortality, note Dr. Susan S. Huang of the University of California Irvine Medical Center and Dr Rpak Detta of the Yale School of Public Health in New Haven, Connecticut.Their current study focused on 281 patients who had an MRSA-positive culture between 2002 and 2005 at a tertiary care center and had also been identified as MRSA-positive at least a year earlier.
The mean age of these "prevalent carriers" was 61.5 years, and the mean time since first evidence of MRSA positivity was 2.4 years. Thirty-five patients (16%) had been known to be MRSA-positive for 4 or more years.
Approximately half had symptomatic infections with MRSA while the others were colonized but asymptomatic at the time they entered the study.
Sixty-five patients (23%) developed a total of 96 additional discrete and unrelated MRSA infections in the year after their detection as prevalent carriers. The risk of subsequent MRSA infection was significantly higher for subjects whose time since first evidence of MRSA positivity was 1-2 years (27%), compared with those whose time since first evidence of positivity was 2 years or more (16%, p = 0.03).
In addition, subsequent MRSA infections were more frequent among patients who were asymptomatically colonized with MRSA than among patients with symptomatic MRSA infections at the time of identification as a prevalent carrier (p = 0.03). The reason for this, the researchers suggested, might be the active therapy received by patients who were MRSA-infected.
Fourteen deaths were associated with MRSA infection.
Although the researchers caution that their results should not be generalized, they conclude that "MRSA carriers remain at considerable risk for subsequent MRSA infection, regardless of the time since the initial detection of MRSA carriage."
Dr. Huang told Reuters Health that they consider these results to be "fairly conclusive."
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