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Swiss Study Suggests Universal MRSA Screening Does Not Reduce Infection Rate

NEW YORK (GenomeWeb News) – Universal screening does not significantly reduce hospital acquired methicillin-resistant Staphylococcus aureus infections in surgical patients, according to a new study.
Researchers in Geneva, Switzerland, did a prospective cohort study over nearly two years aimed at assessing the effectiveness of early MRSA detection for reducing nosocomial, or hospital-acquired, infections. Their findings, published online today in the Journal of the American Medical Association, indicate that universal screening did not decrease infection rates in this particular setting.
“Overall, our real-life trial did not show an added benefit for widespread rapid screening on admission compared with standard MRSA control alone in preventing nosocomial MRSA infections in a large surgical department,” the authors wrote. “To increase effectiveness, MRSA screening could be targeted to surgical patients who undergo elective procedures with a high risk of MRSA infection.”
MRSA, the so-called “superbug,” has become a major public health concern in recent years, causing hospital-acquired infections and — increasingly — infections in community settings. To combat the problem, some health officials, policy makers, and advocacy groups have called for active surveillance — testing all patients who enter the hospital for MRSA. But such universal screening measures remain controversial.
Standard infection control procedures generally call for isolating MRSA carriers, having health care workers use separate hospital gowns, gloves, and, sometimes, masks, for each MRSA patient, giving MRSA patients antibiotic treatments and topical decolonization. Good hygiene, particularly hand washing, is also crucial for preventing the bug’s spread.
In an effort to assess the effectiveness of universal screening, lead author Stephan Harbath and his colleagues compared standard infection control alone with standard infection control plus rapid, molecular screening on admission in 21,754 surgical patients at the University of Geneva Hospitals. For the latter group, any patients admitted for more than 24 hours were screened using a rapid, multiplex polymerase chain reaction test. Twelve different surgical wards participated in the study.
During the first three months — from July to September 2004 — the researchers did baseline MRSA surveillance in all the participating wards without any screening upon admission. For the next nine months, they did universal screening in five surgical wards. The other wards were used as controls. To control for any “ward-related” variables, they switched the intervention and control wards in September 2005 and monitored these for another nine months.
For active surveillance, the researchers used a multiplex, immunocapture-coupled quantitative polymerase chain reaction to detect MRSA in nose swabs. The median time between the swab and notification of results was 22.5 hours. Overall, 10,193 patients were screened for MRSA. Of these, roughly five percent — 515 patients — tested positive for MRSA. While some of these were known carriers, 337 new MRSA carriers were identified.
But the number of patients who actually developed nosocomial infections during the intervention periods was similar to that in the control periods: 93 screened patients — 1.11 per 1,000 patient days — developed MRSA infections versus 76 patients — or 0.91 per 1000 patient days — during the control periods. As well, more than half of the screened patients who ended up with MRSA infections while in the hospital actually tested negative for the bug when they were first admitted.
“We suggest that surgical services and infection control teams should carefully assess their local MRSA epidemiology and patient profiles before introducing a universal screening policy,” Harbath and his team concluded in the paper.
In an editorial in the same issue of JAMA, University of Iowa infectious disease specialist Daniel Diekema and Michael Climo, an infectious disease specialist at the McGuire Veterans Affairs Medical Center in Richmond, Virginia, also argue that there is insufficient evidence to implement universal screening. They call active surveillance culturing an “expensive and complex intervention fraught with the potential for unintended adverse consequences.”
“Achieving lower rates of MRSA infections in hospitals is possible by attending to basic infection control principles and other proven interventions,” Diekema and Climo wrote. “[S]imply expanding the use of [active surveillance culturing] might not help achieve the elusive goal of preventing all MRSA infections.”

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