The estimated total of invasive MRSA infections across the United States fell 31% between 2005 and 2011, according to a report published online Sept. 16 in JAMA Internal Medicine.
And for the first time, the estimated number of hospital-onset invasive MRSA infections was lower than that of community-associated infections, said Dr. Raymund Dantes of the Epidemic Intelligence Service of the Centers for Disease Control and Prevention, Atlanta.
Courtesy Janice Haney Carr/CDC
According to the report, the estimated total of invasive MRSA infections across the United States fell 31% between 2005 and 2011.
The greatest burden of disease continues to fall upon patients in the community who have recent or ongoing exposure to health care services. That includes those recently discharged from acute medical care, long-term–care residents, and patients who require repeated medical visits, such as for diabetes care or dialysis, according to Dr. Dantes and his colleagues.
Those findings, together with other results from their analysis of data in the CDC’s emerging infections surveillance system, indicate that "the U.S. is on track to meet the Department of Health and Human Services 2013 target of reducing health care–associated MRSA invasive infections by 50%," they noted (JAMA Intern. Med. 2013 Sept. 16 [doi:10.1001/jamainternmed.2013.10423]).
To better understand the national burden of invasive MRSA infections, Dr. Dantes and his colleagues analyzed data from nine states participating in the surveillance program: California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New York, Oregon, and Tennessee. They focused on 2011, the most recent year for which complete data are available, and compared the information with that gathered in 2005.
Those nine sites, which represented 16,489,254 people in 2005 and 19,393,677 people in 2011, reported 4,872 cases of invasive MRSA among 4,445 patients in 2011. A total of 18% were classified as hospital-onset infections, 60% as "health-care–associated community onset" infections, and 20% as community-associated infections.
Extrapolating those results to the entire U.S. population, the investigators estimated that 80,461 invasive MRSA infections occurred nationally in 2011, of which 14,156 were hospital-onset, 48,353 were health-care–associated community onset, and 16,560 were community-associated.
"Compared with 6 years earlier, the estimated national rate of invasive MRSA has decreased by 31.2%," Dr. Dantes and his associates said. "Although this rate decrease was most precipitous among hospital-onset infections, at 54.2%, rate decreases were evident among other categories as well: health-care–associated by 27.7%, and community-associated by 5.0%," they wrote.
The 54% decline in hospital-onset cases was particularly encouraging. The exact reason for that reduction is not yet known, but it is likely that implementation of infection prevention measures contributed, especially those targeting intravascular catheter-related infections and health care transmission of multidrug-resistant organisms, they added.
"It is notable that the incidence of community-associated invasive MRSA infections, although relatively stable, has not increased over this time, despite increases in hospitalizations related to MRSA skin and soft-tissue infections documented in discharge data," the investigators said. "Progress in reducing infections among this population is likely to be most challenging due to a lack of clearly effective strategies to control endemic MRSA transmission in the community setting.
Although there is guidance on preventing community-associated MRSA transmission in institutions such as athletic facilities, correctional facilities, and schools, guidance on prevention in other community settings isn’t as well established. Changes in community settings "may be related to transmission in households, prevention of invasive disease from improved early treatment of noninvasive infections, or the natural evolution of this pathogen," they noted.
To substantially reduce the overall burden of invasive MRSA infections, significant progress must be made to prevent postdischarge and dialysis-related cases, the researchers added. In 2011, most cases of health care–associated community-onset invasive MRSA occurred among dialysis patients and patients who had been hospitalized recently.
"Invasive devices that remain placed during the postdischarge period, progression from colonization to clinical infection, and breakdowns in host defense and skin integrity during hospitalization may account for this increased risk," Dr. Dantes and his associates said.
An estimated 11,285 patients with invasive MRSA infections died of all causes during hospitalization in 2011, they added.
The Emerging Infections Program and the National Center for Emerging Zoonotic Infectious Diseases at the Centers for Disease Control and Prevention supported the study. No financial conflicts of interest were reported.