Hospital Admission Screening Fails to Stop MRSA Infections

By Michael Smith
GENEVA, March 11 -- Screening thousands of surgical patients for methicillin-resistant Staphylococcus aureus (MRSA) at or before hospital admission did nothing to prevent nosocomial infections, researchers here found. The finding -- described by the Swiss researchers as "worrisome" -- came as several U.S. states are mandating the use of active surveillance cultures as routine screening for MRSA.One implication of the trial, which involved nearly 22,000 patients, is that early detection alone will not be enough to reduce hospital-acquired MRSA infections, wrote Stephan Harbarth, M.D., and colleagues at the University of Geneva Hospitals in the March 12 issue of the Journal of the American Medical Association.
"It remains to be seen whether a strategy combining early detection, preemptive isolation, and intense promotion of basic infection control measures might be more successful," they added.
"The take-away message here is that you have to know what's going on in your own organization and that comes down to risk assessment," commented Marcia Patrick, R.N., of MultiCare Health System in Tacoma, Wash., speaking for the Association for Professionals in Infection Control and Epidemiology.
"If you're not screening at some point," she said, "you don't know what's out there."
But that doesn't imply that all hospitals should screen all patients all the time, Patrick said. "It all comes down back to risk."
The bottom line, she added, is that "in Geneva, they found it probably wasn't beneficial." Legally mandated screening would take away the "flexibility" of hospitals to match their policies to a known level of risk, Patrick said.
The University of Geneva Hospitals has 12 surgical units in eight specialties. From July to September 2004, a baseline surveillance period without MRSA screening was conducted in all units.
For the next nine months, patients destined for six of the units had rapid MRSA screening, and all units used standard infection control measures for patients with MRSA, including:
Contact isolation of MRSA carriers.
Use of dedicated material, such as gowns and gloves.
Adjustment of perioperative antibiotic prophylaxis of MRSA carriers.
A computerized MRSA alert system.
Topical decolonization with nasal mupirocin ointment and chlorhexidine body washing for five days.
The remaining units did not have the rapid MRSA screening and served as controls.
After nine months, there was a two-month washout period of MRSA surveillance, and then the units were switched, with the control units now using rapid screening and the others serving as controls.
The results appeared to rule out a beneficial effect of screening, Dr. Harbarth and colleagues said:
During the two intervention periods, 10,193 of 10,844 patients (or 94%) were screened.
Screening identified 515 MRSA-positive patients (5.1%), including 337 previously unknown MRSA carriers.
In the intervention periods, 93 patients (1.11 per 1,000 patient-days) developed nosocomial MRSA infection, compared with 76 in the control periods (0.91 per 1,000 patient-days).
The adjusted incidence rate ratio was 1.20, with a 95% confidence interval from 0.85 to 1.69, which was not significant at P=0.29.
The rates of MRSA surgical site infection and nosocomial MRSA acquisition also did not change significantly.
One possible explanation for the finding, the researchers said, is the relatively low rate of MRSA infection at the center. Recent data indicate that the MRSA bacteremia rate in most surgical specialties varies between 0.5 and 1.5 cases per 10,000 patient-days, but it was only 0.36 cases per 10,000 patient-days during this experiment.
Other limitations of the study included failure to screen all patients, use of a rapid diagnostic method (polymerase chain reaction) developed at the institution, average return time for test results of more than 22 hours which was after many of the patients had undergone surgery, and failure of appropriate antibiotic prophylaxis in more than half of the colonized patients even when screening test results were available.
Nevertheless, the finding of this study calls into question the notion of active surveillance as a way to block MRSA infections, commented Daniel Diekema, M.D., of the University of Iowa College of Medicine, and Michael Climo, M.D., of Virginia Commonwealth University, in an accompanying editorial.
"Simply expanding the use of (active surveillance culturing) might not help achieve the elusive goal of preventing all MRSA infections," they wrote.
On the other hand, the results support CDC recommendations that oppose routine or mandated surveillance, they said. "There exists no one-size-fits-all solution to the problem of MRSA prevention," they said.
The study was supported by the University of Geneva Hospitals and the Swiss National Science Foundation. Dr. Harbarth said he has received consulting fees from 3M, BioMerieux, and Roche Diagnostics.
Primary source: Journal of the American Medical AssociationSource reference:Harbarth S et al. "Universal Screening for Methicillin-Resistant Staphylococcus aureus at Hospital Admission and Nosocomial Infection in Surgical Patients." JAMA. 2008;299(10):1149-57. Additional source: Journal of the American Medical AssociationSource reference: Daniel J Diekema and Michael Climo. "Preventing MRSA Infections: Finding It Is Not Enough." JAMA. 2008;299(10):1190-92.