MRSA hospitalizations double from 1999 to 2005

'This is an clearly an epidemic phenomenon'

Hospitalizations related to methicillin-resistant Staphylococcus aureus (MRSA) infections more than doubled, from 127,000 to nearly 280,000, between 1999 and 2005, according to a new study.1 During that same period, hospitalizations of patients with general staph infections increased 62% across the country.

The study found that such infections are now "endemic, and in some cases epidemic," in many U.S. hospitals, long-term care facilities, and communities. The researchers concluded that control of MRSA should be made a national priority.

"I would argue that MRSA has been an endemic disease and it's in the population all the time," says one of the authors, David Smith, PhD, associate professor of emerging pathogens and zoology at the University of Florida in Gainesville. "But a doubling is out of proportion to the normal variance you would see in a population where you are staying steady. We are above the baseline, the 'steady state' for MRSA since 1999. This is clearly an epidemic phenomenon."

Though the study was insufficiently powered to prove the point, Smith thinks the increase is being driven by the rise of community-acquired (CA) MRSA. "Anecdotally, it all points to the increase mainly being community-acquired," he says. "If you look at the increases by cause of infection, you see that cellulitis and abscesses are the ones that have just shot up."

A steady but less dramatic increase was seen over the period for traditional health care-associated infections associated with devices or surgery, he notes. "Just anecdotally talking to emergency room physicians what you are really seeing is a lot of people coming in with [wounds] that have not healed and then it turns out to be MRSA," Smith says. "A lot of those are easily treated, but they can turn into severe infections. I think basically we are seeing a big change in community-acquired MRSA that has been reflected in hospitalizations."

Of interest, the researchers used more stringent mortality criteria and ended up with 11,000 estimated MRSA deaths annually, well below the 18,650 deaths reported in another recent study.2 "We limited deaths to MRSA that we attributed to records where it was listed as one of the first two causes," he explains. "If MRSA was one of the first two primary diagnoses and the patient died, then we called it a MRSA death. They included any death associated with MRSA. In earlier drafts, we considered any deaths associated with MRSA and our number was almost identical to theirs." The estimated incidence of S. aureus was based on hospitalizations with S. aureus-related discharge diagnoses from the National Hospital Discharge Survey (NHDS).

Widespread implications

The indication that community-associated MRSA is spreading rapidly into hospitals has widespread implications, including empirical treatment for infections, the authors warn. In hospitals, hand-washing practices must be improved, they said, echoing the sentiments of many an ICP. "Hand washing really does work, but people really don't wash their hands," Smith says. "They don't see the negative consequences for the patients immediately and they don't see a reward for it if they do it themselves. It's not surprising that they are lax about it."

Ultimately, some system of incentives and accountability may need to be developed to improve the cardinal principle of infection control, he notes. Meanwhile, the increase in skin and soft-tissue infections means standard precautions — including use of gloves — are likely warranted when dealing with all skin and soft tissue infections in outpatient clinics and acute care facilities, the authors recommend. Contact precautions, including use of gowns and gloves, should be implemented for all wound care in acute care facilities, and institutional programs to enhance antimicrobial drug stewardship should be implemented, they conclude. "Clinicians should be aware of the magnitude of the issue and consider MRSA a highly likely cause of skin and soft-skin tissue infections, even in areas where the prevalence of MRSA is believed to be low," they warn.

In addition, the rising incidence of MRSA will likely increase demand for vancomycin, creating more pressure for drug resistance to emerge. The researchers recommend national surveillance or reporting requirements for the infections. "It's a shame that we had to wait this long to get numbers like this," Smith says. "It would have [been better] to have detected and noticed this change and gotten real good numbers on it much earlier than we have."

Hospitals can't do it all

The authors called for more research to explore the interaction between community- and hospital-associated infection, stepped-up efforts to control hospital infection, and increased investment in the development of a staph vaccine. The latter will be particularly important if resistant staph continues to emerge in the community, where prevention efforts are problematic. "Hospitals can certainly play their part, but if this thing is raging in the community it's hard to imagine how hospital infection control is going to do anything," Smith says. "If this is something you get playing football, sitting on a bench where someone else has sat or touching a doorknob, it is not going to go away because hospitals are doing their part."

References

  1. Klein E, Smith DL, Laxminarayan R. Hospitalizations and deaths caused by methicillin-resistant Staphylococcus aureus, United States, 1999-2005. Emerg Infect Dis 2007 Dec. Available from www.cdc.gov.
  2. Klevens RM, Morrison MA, Nadle J. Invasive methicillin-resistant Staphylococcus aureus infections in the United States. 2007; 298:1,763-1,771.