Can A New Molecular Test Enhance MRSA Detection?

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By Brian McCurdy, Associate Editor
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Given the substantial rates of methicillin resistant Staphylococcus aureus (MRSA) infection in hospitals, early detection is vital to ensure timely and appropriate treatment. A new molecular test may significantly decrease the amount of time it takes to detect MRSA and possibly reduce transmission of the bacteria, according to the authors of a new study. Researchers who conducted the two-year study, recently published in Critical Care, evaluated over 1,000 patients who had been admitted for longer than 24 hours to a medical intensive care unit (ICU) or surgical ICU. Authors of the study used the quick, multiplex immunocapture-coupled PCR (qMRSA) test to identify MRSA in the DNA on patient swabs. The median time between admission to the ICU and the notification of MRSA colonization decreased with the qMRSA test from 87 to 21 hours in the surgical ICU, compared with historical culture results, according to the study. Researchers say the quicker testing saved 1,227 preemptive hours of isolation for the 245 patients who were negative for MRSA. In addition, the study says the notification time in the medical ICU decreased from 106 to 23 hours. Furthermore, the on-admission screening identified the prevalence of MRSA to be 6.7 percent in the ICU patients, notes the study. Without the qMRSA test, researchers say hospital clinicians would have missed MRSA in 55 carriers. The on-admission screening and preemptive isolation led to a decrease in MRSA infections acquired in the medical ICU but did not affect the infections acquired in the surgical ICU, according to the study. What Are The Implications Of The Test? David G. Armstrong, DPM, MSc, PhD, who is “very familiar” with the promise of the qMRSA test, feels the testing, once perfected and disseminated, would permit quicker screening of MRSA and clinicians would be able to isolate infected patients more quickly. While the test would not immediately impact MRSA rates, it would give clinicians the capability of narrowing the spectrum of their antibiotic regimen more quickly, notes Dr. Armstrong, a Professor of Surgery, Chair of Research and Assistant Dean at the William M. Scholl College of Podiatric Medicine at the Rosalind Franklin University of Medicine in Chicago. Accordingly, he says practitioners would be less likely to use anti-MRSA drugs inappropriately. Benjamin A. Lipsky, MD, says the new test could potentially reduce MRSA transmission. “If the test quickly identified colonized/ infected patients, were safe and reasonably priced, and positive cultures resulted in effective MRSA eradication, it might reduce MRSA transmission among patients and between hospital and community,” says Dr. Lipsky, a Professor of Medicine at the University of Washington School of Medicine. While the testing appears helpful in the earlier identification of MRSA, Dr. Lipsky would prefer to see the study replicated in other institutions and for the comparator to be standard culture rather than historical controls. As he notes, the efficacy of cohorting patients infected or colonized with MRSA (or other epidemiologically significant organisms) remains unclear and the results may depend on the background prevalence of MRSA in a particular hospital. Dr. Armstrong feels the testing would be practical in a hospital or VA setting. However, Dr. Lipsky says the practicality of such testing in those settings depends on the validated accuracy and cost of the testing. As he points out, once a hospital’s prevalence of methicillin resistance among S. aureus isolates reaches a certain threshold, perhaps 30 percent, it is difficult to eradicate the MRSA from the center. BMS Revises Prescribing Data For Gatifloxacin By Brian McCurdy, Associate Editor Following reports that gatifloxacin (Tequin) may not be safe for use in patients with diabetes, the drug’s manufacturer, Bristol-Myers Squibb, has revised the drug’s prescribing information. Accordingly, gatifloxacin is now contraindicated in diabetic patients due to serious reports of hypoglycemia and hyperglycemia. Tequin is a newer generation quinolone with an FDA indication for uncomplicated skin and skin structure infections. A recent study in Clinical Infectious Diseases documented the rates of glucose homeostasis abnormality (GHA) adverse event reports (AERs) of gatifloxacin as compared to fellow quinolones levofloxacin, ciprofloxacin and moxifloxacin.

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