Simple Test for Drug-Resistant Bacterium

A fast molecular test could help hospitals quickly identify patients to be quarantined.

A sensitive new diagnostic test for methicillin-resistant Staphylococcus aureus (MRSA)--a drug-resistant bacterium that can run rampant in hospitals--could help broaden access to fast, cheap testing. The test, being developed by Adnavance Technologies, a startup in San Diego, is simpler to perform than existing molecular diagnostics, potentially making it accessible to hospitals without sophisticated labs. Researchers hope that this will enhance surveillance efforts and help stem hospital-centered outbreaks.

MRSA, a variant of the bacterium that causes most staph infections, is commonly found in hospitals, where it can be passed between health-care workers and patients--often those with weak immune systems; it accounts for more than half of hospital-acquired infections in the United States. Not everyone who is infected with MRSA shows symptoms, making it difficult to determine who carries the potentially deadly bug.

In an effort to stop hospital outbreaks, a growing number of states require that hospitals test patients for MRSA before admitting them, or are considering legislation that would require them to do so. The entire Veterans Administration health system now requires patient screening, and the practice has been in place in Australia and some European countries for years.

To identify whether a patient is infected with MRSA, hospitals either culture bacteria collected from nasal and other samples, which can take several days, or perform newer molecular tests, which are much more expensive. Only about 35 percent of hospitals in the United States are certified to perform the newer type of testing. The others must send samples out for analysis, which can also take time. "If you're going to isolate patients, the faster you can know who is colonized, the better," says Phil Polgreen, director of the Infectious Disease Society of America's Emerging Infections Network and an epidemiologist at the University of Iowa, in Iowa City. "With the culture studies, you don't know a patient's status for a few days. In that time, the infection could have spread."

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In states where hospital screening is required, patients must be quarantined until test results are in--a move that is both costly to hospitals and potentially dangerous for patients. Some studies also suggest that patients in isolation receive less attention from staff.

Adnavance is developing a new test that can detect MRSA bacteria directly, without requiring that the DNA be amplified, as is done in existing molecular tests. The central technology is a gold electrode coated with a proprietary marker that binds to the drug-resistant bacteria. As current flows through the electrode, it attracts negatively charged DNA, generating an easily detectable change in the surface charge of the electrode.