NEW YORK (GenomeWeb News) – Researchers conducting a study over a nearly four-year period at three hospitals in the Chicago area found that universal surveillance of methicillin-resistant Staphylococcus aureus decreased the rate of MRSA infections by more than half compared to no MRSA testing.
The results of the study, published today in the Annals of Internal Medicine, directly contradict the findings of a Swiss research group published last week in the Journal of the American Medical Association.
Ari Robicsek and colleagues from the Evanston Northwestern Healthcare system in Illinois undertook a nearly four-year study to determine whether universal MRSA screening would cut the rate of MRSA infection at the three hospitals that make up the system. All told, Evanston Northwestern admits roughly 40,000 patients each year.
The study was divided into three periods: the first was the baseline, which was conducted over the first 12 months and had no active MRSA surveillance; the second period was the following 12 months and included MRSA surveillance for all admissions to the intensive care unit; the final period lasted 21 months and included universal surveillance of hospital admissions.
The primary outcome measure of the study was the rate of clinical hospital-associated MRSA infections. The authors considered infections that occurred more than two days after admission and within 30 days after discharge as being hospital-associated.
Using a home-brew real-time polymerase chain reaction test and a commercially available molecular diagnostic assay for MRSA sold by Becton Dickinson, the researchers found that “rates of MRSA bacteremia statistically significantly decreased after implementation of universal surveillance compared with baseline values.”
The researchers found that prevalence density of MRSA clinical infection decreased from 8.9 per 10,000 patient days during the baseline period to 7.4 in the second period and 3.9 in the final period, when universal surveillance was conducted.
The study did not include a concomitant, unscreened control group. However, the researchers found that while the rate of MRSA infection had a statistically significant decrease compared with baseline, the methicillin-susceptible S. aureus bacteremia rate did not statistcially significantly change during the three monitoring periods.
“The program was associated with a reduction by more than half of health-care-associated MRSA bloodstream, respiratory, urinary tract, and surgical site disease occurring during admission and in the 30 days after discharge,” the authors concluded.
Those findings are at odds with the study published week in JAMA, which concluded that universal screening does not significantly reduce hospital-acquired MRSA infections in surgical patients. The design of that study was criticized by makers of MRSA molecular diagnostic tests, particularly Cepheid.
The Evanston Northwestern researchers believe that their study is the first large-scale, universal admission MRSA surveillance program conducted in the US.
Though the study received no external funding, AIM noted that some of the authors have received grants from firms that are developing or already sell molecular diagnostic tests for MRSA screening, including Becton Dickinson, Cepheid, Roche, and Nanosphere.