Invasive, hospital-onset methicillin-resistant Staphylococcus aureus infections decreased "dramatically and significantly" by 9.4% per year from 2005 to 2008, a Journal of the American Medical Association report says.
Additionally, there was a 5.7% decrease per year in the incidence of healthcare-associated or community-onset MRSA infections, (infections in patients who had symptom onset outside the hospital but who had recently been admitted or had been an outpatient).This is the first study of its kind to reflect MRSA findings among outpatients who may have acquired their infections in healthcare settings.
This translates to a 28% decrease in hospital-onset invasive MRSA infections and about a 17% decrease in invasive healthcare-associated or community-onset infections over the period studied.
For the study, JAMA collected lab reports from nine diverse metro areas representing 15 million people.
In all measures, the authors wrote, use of prevention strategies shows that the national priority to reduce these infections has been a success, although "more challenges remain. Increasing adherence to existing recommendations and addressing MRSA transmission and prevention beyond inpatient settings" require further effort.
The report was published in Tuesday's edition of JAMA by researchers from the Centers for Disease Control and Prevention, in collaboration with other investigators in nine states: Georgia, Connecticut, Colorado, California, Maryland, Minnesota, New York, Oregon, and Tennessee.
"Our findings complement those from several smaller studies of infection prevention interventions, which demonstrate decreases in MRSA infections at individual or small collections of facilities," the authors wrote. In England, hospitals reduced MRSA infections from 2003 to 2008 by 57% after a UK Department of Health set a goal to reduce them by half.
The authors wrote that they could not say why the infection rates have dropped, "a number of factors might have contributed, including the dissemination of MRSA prevention practices in many U.S. hospitals."
Eight of the sites demonstrated a decrease, six of which were statistically significant, but one site experienced a significant increase over the period.
A subset analysis limited just to bloodstream infections showed a 34% decrease in all hospital-onset cases and a 20% decrease in health-care associated or community onset cases. The authors wrote that "much of the estimated reduction in these infections might have been due to the dissemination of inpatient central line-associated BSI prevention efforts rather than MRSA-specific prevention efforts," specifically, the Michigan Keystone ICU project and the Pittsburgh Regional Health Initiative Project.
The only group that did not see a consistent decline was that isolated for patients undergoing dialysis, a category in which most of the decline occurred in 2008.
In an accompanying editorial, Eli Perencevich, MD and Daniel Diekema, MD of the University of Iowa Carver College of Medicine suggest the decline in infections began earlier than specific MRSA prevention campaigns, "and such interventions still have not been implemented in many U.S. hospitals.
"Therefore, the observed declines in MRSA reported may instead be the result of general infection control efforts such as wider adoption of alcohol-based hand rubs, improved hand hygiene compliance, efforts targeted at eliminating central line-associated bloodstream infections and enhanced antimicrobial stewardship programs."
The authors also note that "natural biological trends," such as the emergence and disappearance of bacteria clones, "are likely to override the best-laid attempts at infection control of all staph infections, not just MRSA.
Also, they wrote, robust surveillance systems are lacking for additional metropolitan areas, and even those are only tracking MRSA as a sole pathogen. "Continued surveillance for S aureus and the other important healthcare-associated pathogens (eg, Enterobacteriaceae, Pseudomonas, Acinetocbacter, Candida)" is essential for informing and targeting infection prevention efforts.