If you are admitted to one of the 320 intensive-care units at HCA Inc.’s hospitals, you will be bathed with germ-killing soap and administered an antibiotic nose ointment twice daily for five days.

HCA, the largest chain of for-profit hospitals in the U.S., has adopted this regimen after studying the best ways to reduce infections due to antibiotic-resistant bacteria, or “superbugs” such as MRSA, which can be deadly for patients after surgery or illness.

Though bacteria can spread among hospital patients from health-care worker’s hands and contaminated objects, infections can also be caused by the bacteria normally on our skin or in our noses, such as Staphylococcus aureus. About a third of people are colonized with staph, and some estimate that another third are intermittent carriers. It usually doesn’t cause illness, but if the bacteria enter the body, such as through an incision, it can lead to infections in the bloodstream, lungs and surgical sites.

Close to half of these staph bacteria have become resistant to antibiotics that include methicillin, making them more difficult to fight. Researchers are trying to find the most effective methods for getting rid of the bacteria carried by patients without increasing the risk of making the bugs even more resistant to antibiotics. The last frontier of attack for hospitals has become patients’ own bodies.

To be sure, hospitals have reduced MRSA infections with better hand washing and hygiene precautions, screening and isolating patients who are carriers. The Centers for Disease Control and Prevention estimates that the incidence of health care-associated MRSA decreased by 5.36 percent in 2014, compared with 2013, while community infections rose slightly in the same period. In total, CDC estimates 72,444 patients had invasive MRSA infections in 2014 and 9,194 died. But limits to surveillance may underestimate MRSA infections, experts say.

“Everyone was resting on their laurels because we’ve been able to reduce MRSA, largely from hospital efforts to reduce infection risk,” says Susan Huang, professor of infectious diseases at the University of California Irvine. “But these are preventable infections and we should be able to drive them down to zero. “

Dr. Huang is lead investigator in a number of prevention studies that include researchers at Harvard Medical School and Rush University. She led Reduce MRSA, the first major study of the approach known as “universal decolonization,” which calls for treating incoming ICU patients with preventive bathing with the germ-fighting soap chlorhexidine and the administration of a nasal antibiotic ointment, mupirocin. The study took place at 74 ICUs in 43 HCA hospitals and compared the approach to two others: the routine practice of screening all patients and isolating those with current or previous colonization or infection, and adding the cleansing and nasal ointment regimen to screening and isolation of MRSA carriers or infected patients.

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