MRSA infections are more common than previously thought in the United States. MRSA (methicillin-resistant Staphylococcus aureus) is being found more frequently outside of health care settings and seems to affect specific populations more than others, explains an article in The Journal of the American Medical Association (JAMA), October 17th issue.

MRSA has become the most common cause of soft tissue and skin infections among emergency department patients in the US – it can cause serious, and even fatal invasive disease, explain the authors. “As the epidemiology of MRSA disease changes, including both community- and health care – associated disease, accurate information on the scope and magnitude of the burden of MRSA disease in the U.S. population is needed to set priorities for prevention and control.”

R. Monina Klevens, D.D.S., M.P.H., CDC (Centers for Disease Control and Prevention), Atlanta, and team carried out a study to find out what the incidence of invasive MRSA disease was in specific American communities during 2005 – and to use this data to extrapolate what invasive MRSA infection figures might be for the country as a whole. It was a population-based surveillance study for invasive MRSA in nine sites participating in the Active Bacterial Core surveillance (ABCs)/Emerging Infections Program Network during the period July 2004 to December 2005. The investigated MRSA reports were classed as either originating at a hospital (health care associated) or originating outside a hospital setting (community associated).

The researchers explain that during the surveillance period there were 8,987 cases of invasive MRSA. 58.4% (5,250) were community onset infections, 26.6% (2,389) were hospital-onset infections and 13.7% (1,234) were community associated infections, while 1.3% were not classifiable.

The scientists calculated that the incidence rate of invasive MRSA in the USA as a whole was 31.8 per 100,000 persons, after factoring in age, race and sex. Rates were higher for people aged 65 years or more at 127.7 per 100,000. Incidence among blacks stood at 66.5% per 100,000, and males at 37.5 per 100,000. For people aged 5-17 years rates were 1.4 per 100,000 (the lowest).

The researchers said “Based on 8,987 observed cases of MRSA and 1,598 in-hospital deaths among patients with MRSA, we estimate that 94,360 invasive MRSA infections occurred in the United States in 2005; these infections were associated with death in 18,650 cases.”

Molecular testing detected strains typically linked to community-associated disease outbreaks collected from cultures in hospital-onset as well as community-onset health care-associated infections in all surveillance areas.

The researchers concluded “In conclusion, invasive MRSA disease is a major public health problem and is primarily related to health care but no longer confined to acute care. Although in 2005 the majority of invasive disease was related to health care, this may change.”

“Invasive Methicillin-Resistant Staphylococcus aureus Infections in the United States”
R. Monina Klevens, DDS, MPH; Melissa A. Morrison, MPH; Joelle Nadle, MPH; Susan Petit, MPH; Ken Gershman, MD, MPH; Susan Ray, MD; Lee H. Harrison, MD; Ruth Lynfield, MD; Ghinwa Dumyati, MD; John M. Townes, MD; Allen S. Craig, MD; Elizabeth R. Zell, MSTAT; Gregory E. Fosheim, MPH; Linda K. McDougal, MS; Roberta B. Carey, PhD; Scott K. Fridkin, MD; for the Active Bacterial Core surveillance (ABCs) MRSA Investigators
JAMA. 2007;298:1763-1771.
Click here to see Full Article online in JAMA

Written by: Christian Nordqvist