There is light at the end of the infection control tunnel – particularly when it comes to the growing incidences of methicillin-resistant Staphylococcus aureus (MRSA) infections – with the FDA's clearance this week of Cepheid's (Sunnyvale, California) GeneXpert MRSA/SA Skin and Soft Tissue Infection (SSTI) test, which can provide clinicians with results in less than a hour, compared to traditional cultured tests which can take days.

"This is the first FDA-cleared test to go straight to a clinical specimen and diagnose the presence of staph and MRSA," David Persing, MD, PhD, executive VP, chief medical & technology officer, told Diagnostics & Imaging Week. "It's the only polymerase chain reaction [PCR] system that allows stat tests to be performed in the lab. Samples can be run as they come in and delivered in a time frame that's actionable to the clinician right away."

The test, which requires just a swab of the infected wound site, runs on Cepheid's GeneXpert system.

In less than one hour, Cepheid's GeneXpert processes specimens from the swabs to determine if a patient is infected with MRSA or S. aureus, giving physicians and surgeons a new tool to aid in selecting the most effective antibiotic therapy to improve patient management.

There are an estimated 292,000 hospitalizations with a diagnosis of S. aureus infection annually in U.S. hospitals. Of these, approximately 126,000 hospitalizations are related to MRSA.

Last year Cepheid received FDA clearance to market its GeneXpert MRSA test for infection control surveillance purposes.

"Not every hospital has a program for surveillance, but every hospital does deal with MRSA," Persing said. "This product deals with the issue of getting an answer back to the clinicians so that they can make appropriate treatment decisions quickly. Most of the time, patients are treated with the wrong drugs for MRSA [because it takes days to get test results back]."

Each GeneXpert test will cost $75 while the system to run the tests, GeneXpert costs $20,000 or more. Prices are higher for systems that have the capacity to run more tests simultaneously.

While the testing system may be costly, the operator does not have to be specially trained.

"Any lab tech can run this test," Persing said. "They don't have to be molecular diagnostics specialists. Because it's so easy to perform, it can be run around the clock. There are no special skill requirements that would prevent someone from doing the tests."

Globally, Cepheid has already sold and installed more than 700 GeneXpert systems, mostly in North American.

"The value of the technology will be especially recognized among surgeons, intensive care unit specialists and emergency room physicians who need information on the right treatment strategy," Persing said. "We think that the drivers will be the end users: surgeons and surgical directors of intensive care units."

Persing also said that he believes that this is a critical test for drugs companies selling MRSA therapies. "We think a lot of pharmaceutical companies are interested in this as the test to make a treatment decision between one pharmaceutical agent or another," he said, adding that Zyvox from Pfizer (New York) is one of the few drugs that effectively treats MRSA.

"So there are a lot of treatment algorithms spurred by these test results and we think co-marketing deals with pharmaceutical companies are possible. In general, we're seeing a trend to target therapy and bring diagnostic testing into the treatment algorithms."

The Centers for Disease Control and Prevention (CDC; Atlanta) reports approximately 12 million patient visits in the U.S. each year for skin infections. MRSA is a bacterium that has become resistant to multiple antibiotics including penicillin and cephalosporins. Current culture-based lab testing methods require up to 72 hours to determine if a skin or soft tissue infection is caused by MRSA or S. aureus. As a result, physicians and surgeons often prescribe broad-spectrum antimicrobial therapies while awaiting culture results.

The Institute of Healthcare Improvement (Cambridge, Massachusetts) reports that about 800,000 surgeries are complicated by infections annually. Cost to the healthcare system to treat these infections is estimated at $9.5 billion, largely due to extended hospital stays following surgery.

The GeneXpert system is a closed, self-contained, fully-integrated and automated platform. It combines on-board sample preparation with real-time PCR amplification and detection functions for automated nucleic acid analysis. The system is designed to purify, concentrate, detect and identify targeted nucleic acid sequences thereby delivering answers directly from unprocessed samples.