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How Does Staph Spread in Hospitals?

New research sheds light on the spread of staph infections—and might provide some useful tips for its prevention.
(Photo: michaeljung/Shutterstock)

(Photo: michaeljung/Shutterstock)

One of the unfortunate risks of spending time in a hospital is catching a staph infection, especially its antibiotic-resistant strain. Now, researchers have used small, wireless transmitters worn by patients and health care workers to track how the bacteria spreads—and perhaps find a way to keep it from spreading any further.

While methicillin-resistant Staphylococcus aureus, better known as MRSA, has been on the decline in recent years and isn't quite the superbug it was once made out to be, it's still a significant public health threat for patients being treated in hospitals, as well as the doctors, nurses, and other employees working there. That makes understanding exactly how the disease spreads—for example, who passes staph to whom, or whether it's picked up from contaminated equipment—a concern of special importance.

To address that issue, Thomas Obadia, a graduate student at France's Pierre Louis Institute of Epidemiology and Public Health, and colleagues outfitted 329 patients and 261 health care workers at Berck-sur-Mer Hospital, a long-term care and rehabilitation facility in northern France, with small wireless transceivers. Every 30 seconds, each transceiver recorded to a flash memory drive the identity of any other people within about a meter and a half, or about five feet—over the four months of the study, that worked out to about 85,000 "close proximity interactions" (CPIs) per day, on average. In addition to the sensor data, each person was tested for each of 48 strains of staph, including MRSA, every week using a nasal swab.

Their results are the first clear evidence of the role that dynamic contact networks connecting patients and hospital workers play in spreading MRSA and other strains of staph in hospitals.

Analyzing the sensor and swab data together revealed that 48 percent of new staph infections could be linked to a CPI with an infected person, and another 38 percent were linked to a sequence of two interactions, that is, one person passed staph to another, and that person passed it on to a third via CPIs. Furthermore, health care workers were about 20 percent more likely to act as intermediaries in the second scenario.

"The contribution of the contact network between patients and [health care workers] in explaining hospital associated infections is widely accepted, although it has never been tested empirically," the team writes today in PLoS Computational Biology. Their results, they argue, are the first clear evidence of the role that dynamic contact networks connecting patients and hospital workers play in spreading MRSA and other strains of staph in hospitals.

The results also suggest a new approach to preventing that spread. Hospitals could, for example, outfit their employees and patients with CPI trackers and use the data to evaluate risks and plan better measures for preventing staph transmission, the team writes.

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