Hospital study shows how bacteria spreads among patients, staff, surfaces

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Researchers tracked the spread and succession of bacterial colonies in a new hospital's first year.

A new study that maps the spread of bacteria in a hospital’s first year of existence will help healthcare leaders better understand the dynamics of a hospital’s microbiome and actions they can take to decrease harmful contact. 

The study, published in Science Translational Medicine, began two months prior to the opening of the University of Chicago’s Center for Care and Discovery and continued for 10 months. Researchers swabbed hospital surfaces in patient care rooms, including bedrails and faucet handles, and collected more than 10,000 samples from 252 patients. They also gathered samples from each unit's nursing staff, swabbing their hands, gloves, shoes, nursing station countertops, pagers, shirts, chairs, computers, landlines and cell phones. Microbial DNA was detected in 6,523 samples.

The results demonstrated a number of interesting trends, beginning with the replacement of organisms typically found in soil and water with those associated with human skin, particularly Corynebacterium, Staphylococcus and Streptococcus, according to a study announcement. The study showed some microbes survived regular disinfections and cleanings with ammonium or bleach.

"Before it opened, the hospital had a relatively low diversity of bacteria. But as soon as it was populated with patients, doctors and nurses, the bacteria from their skin took over," said study author Jack Gilbert, director of the Microbiome Center at the University of Chicago and group leader in Microbial Ecology at Argonne National Laboratory, in the announcement.

A second, and ongoing, set of changes followed each patient's hospital admission. On a patient's first day in the hospital, microbes tended to move from surfaces in the patient's room—bedrails, countertops, faucet handles—to the patient. "By the second day of their stay," Gilbert said, "the route of microbial transmission was reversed. Within 24 hours, the patient's microbiome takes over the hospital space."

Gilbert told Live Science that knowledge of these movements could be useful as hospitals seek ways to reduce the chances of survival for harmful bacteria. For example, the team’s finding that different types of microbes tended to be found on different types of surfaces can provide useful information about microenvironments that could potentially guide hospitals in their choices of surface materials.

Interestingly, the microbes moving between a patient’s skin and room surfaces were little affected by medical treatments other than topical antibiotics. “We consistently found that antibiotics given intravenously or by mouth had almost no impact on the skin microbiome,” said Gilbert in the announcement.

Other noteworthy findings included a greater propensity for bacterial exchange among staff in the summer, possibly due to increased humidity. The study also found a greater number of antibiotic-resistant bacteria on surfaces in rooms with patients who had long hospital stays.