July 5, 2012

MRSA Rates Are on the Decline

(Ivanhoe Newswire) — An analysis of more than 9 million Department of Defense non-active and active duty personnel revealed that the rates of both community-onset and hospital-onset methicillin-resistant Staphylococcus aureus (MRSA) bacteremia decreased from 2005 to 2010, while the proportion of community-onset skin and soft tissue infections from MRSA has more recently declined.

The background information in the article states that the magnitude of invasive MRSA infections as well as the emergence of community-onset MRSA infections in the United States has been well-documented. The article also reveals that skin and soft tissue infections (SSTIs) have become a significant public health issue for the U.S. military, and rates of hospital-onset MRSA infections are reported as decreasing, though recent rates of community-onset S aureus infections are less known.

The study conducted by Michael L. Landrum, M.D. of the San Antonio Military Medical Center, Fort Sam Houston , Texas, and colleagues examined the incidence rates of community-onset and hospital-onset S aureus bacteremia and SSTIs and the proportion due to MRSA in a large population composed of individuals of all ages from all U.S. regions. They analyzed findings using an observational study of all Department of Defense TRICARE beneficiaries from January 2005 through December 2010. Medical record databases were used to identify and classify all annual first-positive S aureus blood and wound or abscess cultures as methicillin-susceptible S aureus (MSSA) or MRSA, and as community-onset or hospital-onset infections (isolates collected after 3 days of hospital admission).

From 2005 to 2010, there were more than 9.2 million people that were eligible to receive care within the Department of Defense healthcare system. In 2005, 52 percent of individuals in the study were men and 84 percent were non-active duty. There were 2,643 blood and 80,281 wound or abscess annual first-positive S aureus cultures included in the study for further analyses. Community-onset infections accounted for 2,094 (79-percent) cases of S aureus bacteremia and 79,801 (99-percent) cases of S aureus SSTIs. The rate of community-onset MRSA bacteremia was higher for individuals who were 65 years or older, and men versus women. 58-percent of community-onset S aureus SSTIs were due to MRSA, higher than for either community-onset bacteremia (39-percent) or hospital-onset SSTIs (53 percent). 54-percent of hospital-onset bacteremia cases were due to MRSA.

The study revealed that the annual incidence rates for community-onset and hospital-onset MRSA bacteremia decreased from 2005 to 2010, peaking at 62-percent in 2006 and decreasing annually to 52-percent in 2010.

The authors highlighted the fact that the rates of hospital-onset MRSA bacteremia significantly decreased and that rates of both community-onset and hospital-onset MRSA bacteremia decreased in parallel. The annual rates of community-onset MSSA bacteremia also significantly decreased. The proportions of both community-onset and hospital-onset S aureus bacteremia due to MRSA did not significantly change though, which suggest balanced decreases in the rates of both MRSA and MSSA bacteremia. For community-onset MRSA SSTIs, there was no significant overall trend in annual rates, but the proportion of community-onset SSTIs due to MRSA declined significantly. Within the U.S. Military Health System, S aureus bacteremia and SSTIs still remain a substantial burden, so emphasis should be placed on successful prevention and treatment strategies.

The authors were quoted as saying, “These observations, taken together with results from others showing decreases in the rates of healthcare-associated infections from MRSA, suggest that broad shifts in the epidemiology of S aureus infections may be occurring. Additional studies are needed to assess whether these trends will continue, which prevention methods are most effective, and to what degree other factors may be contributing.”

Source: JAMA, July 2012