MRSA 10X More Prevalent Than Previously Thought

By Judith Graham
Chicago Tribune staff reporter
June 25, 2007

As many as 1.2 million hospital patients are infected with dangerous, drug-resistant staph infections each year, almost 10 times more than previous estimates, based on findings from a major new study.

And 48,000 to 119,000 hospital patients a year may be dying from methicillin-resistant staphylococcus aureus (MRSA) infections, far more than previously thought, the study suggests.

The Tribune obtained the results during the weekend from the Association for Professionals in Infection Control & Epidemiology (APIC), which is releasing the report publicly on Monday. The author is Dr. William Jarvis, former acting director of the hospital infections program at the Centers for Disease Control and Prevention.

The findings come amid mounting public concern about the spread of antibiotic-resistant bacteria in health-care facilities and community settings. Medical experts consider the rise of so-called superbugs such as MRSA, a leading cause of deadly blood infections and pneumonias, one of the most alarming public health threats in the nation.

"We're hoping this survey is a wake-up call to health-care workers across America," said Kathy Warye, the association's executive officer.

It is the largest, most comprehensive survey of MRSA in health-care facilities to date. It's based on surveys sent last year to 10,000 infection-control practitioners, including doctors and nurses in hospitals, nursing homes and rehabilitation facilities.

Health-care professionals were asked to select one day between Oct. 1 and Nov. 10, 2005, and report all known MRSA cases in their institutions. More than 1,200 hospitals and 100 nursing homes and rehabilitation facilities responded, supplying data about patients with MRSA infections and patients colonized with the bacteria.

People colonized with MRSA typically carry it in their nose without being symptomatic. They're at risk of passing the superbug to others unknowingly by wiping their nose and then touching a table that a doctor or nurse later touches, for instance. MRSA can live on surfaces for days or even weeks.

The new survey confirms what's been observed anecdotally for years -- MRSA is rampant in health-care facilities.

It found that 34 of 1,000 patients in the survey had active MRSA infections and that 12 were colonized with the superbug, for a total MRSA prevalence rate of 46 per 1,000 patients. (In Illinois, the prevalence rate was 37 per 1,000 patients, based on responses from 74 hospitals and other acute-care facilities.)

The most widely cited previous study, published by CDC researchers in June 2005, had estimated that the MRSA infection rate at in-patient hospitals was 3.9 per 1,000 patients. Based on that rate, it estimated that 126,000 patients were infected with the superbug each year.

The new report didn't translate its findings into actual numbers, but Jarvis outlined a means of doing so to the Tribune. He said it was important for the public to see the ballpark figures.

The calculation involves 35.2 million people hospitalized in the U.S. in 2005, the latest year for which information is available. Applying the prevalence rates in the new study, the data suggest that 1.2 million hospital patients are afflicted with MRSA each year and that an additional 423,000 patients are colonized with the superbug.

This is only an estimate, subject to the accuracy of the numbers reporting by infection-control practitioners and the limitations of a "single point in time" snapshot of the data, Jarvis said. Many hospitals don't routinely test patients to see whether they're colonized with MRSA, he said. Also, the findings haven't been peer-reviewed, which is standard in scientific publications.

"Most hospital leaders are paying very close attention to infections within their institutions. ... But I think this tells us that MRSA is an even bigger problem than we thought it was," said Nancy Foster, vice president of quality and patient-safety policy at the American Hospital Association, after reviewing an advance copy of the APIC report.

Dr. John Jernigan, a medical epidemiologist at the CDC and the agency's lead expert on MRSA, said he "applauded the study" even though he hadn't examined its results or methodology. He has co-written articles on MRSA with Jarvis that appeared in leading infection-control publications.

"Everything we're finding is telling us the same thing: MRSA is an enormous problem in health-care facilities, more needs to be done to prevent it, and hospitals need to make infection control more of a priority," Jernigan said.

The CDC has said at least 5,000 patients die after being infected by MRSA at surgical sites, in their blood or in their lungs. That's a mortality rate of 4 percent, assuming a base of 126,000 patients. Using new prevalence estimates of 1.2 million MRSA patients a year, it suggests 48,000 patients a year may die of MRSA.

There is considerable uncertainty about the mortality rate associated with MRSA, however, and it may be as high as 10 percent, said Dr. Lance Peterson, director of infectious disease research at Evanston Northwestern Healthcare. Using the new estimates, that suggests as many as 119,000 hospital patients a year may be felled by the superbug.

To put that figure in context, the Institute of Medicine has estimated that nearly 100,000 patients die of 2 million infections acquired in hospitals every year. MRSA constituted only a portion of those infections and deaths. The new numbers suggest the actual number of hospital-related infections and deaths could be much larger.

An important finding in the new study suggests that hospitals may not be focusing infection-control strategies on the right locations in their institutions. Though earlier research has indicated intensive-care units, which often treat patients with compromised immune systems, are hot spots of infection, this report shows that 67 percent of patients with MRSA infections were on medical wards.

"This suggests that MRSA has become a problem throughout the institution and that [hospital staff] may need to look for it beyond the ICU," Jarvis said.

The study shows that 77 percent of patients with MRSA were identified within two days of entering a hospital, making it likely they were colonized or infected before being admitted. The vast majority of these patients picked up MRSA during an earlier stay at a hospital or nursing home, Jarvis said.

On the positive side, there is strong consensus about the steps hospitals need to take to control MRSA, said Dr. Don Goldmann, a senior vice president at the Institute for Healthcare Improvement in Boston.

All health-care workers should practice rigorous hand-washing, and all institutions should have robust programs for disinfecting medical equipment and patients' rooms, he said. When patients are known to have MRSA, hospital staff should wear gowns and gloves to prevent transmission. And patients deemed at risk of carrying MRSA should be screened to determine where bacterial hot spots are festering.

"Now that the true extent of this scandalously tragic epidemic is known, I hope that health-care leadership will finally confront it with the effective means that have always been available," said Michael Bennett, president of the Coalition for Patients' Rights in Maryland.
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