Bacterial infections can imperil the fragile patients at hospitals‘ intensive care units. And a new study reveals an unlikely spreader: the health care workers who treat them. The standard sterile hospital garb typically thought to prevent infections isn’t helping.

Physical barriers are the most effective way to block invisible intruders like the bacteria responsible for methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) infections, which are among the most common hospital-acquired pathogens. Such strains, which are resistant to most antibiotic treatments, contribute to more than $4 billion in health care costs for treating the skin lesions, respiratory symptoms and sepsis that the bacteria cause.

It’s hardly been clear that requiring all health care workers to put on gowns and gloves before visiting each patient, then discarding and re-robing before visiting the next patient, would help to reduce the spread of such infections in ICUs. The Centers for Disease Control currently recommends that workers suit up with gowns and gloves before caring for patients with known MRSA or VRE infections, but researchers led by Dr. Anthony Harris at the University of Maryland School of Medicine wanted to see how effective universal gowning and gloving would be in lowering the number of new cases of disease in ICUs.

MORE: Death By Bacteria: The Dangers of Drug Resistant Bugs

From January 2012 to October 2012, Harris and his colleagues asked health care workers at 10 ICUs around the country to wear gowns and gloves every time they cared for a patient. Workers at another 10 hospitals with similar ICU settings followed existing protocols of suiting up only for patients with known infections. The team collected swabs from more than 26,000 patients during that time, and tested them for MRSA and VRE.

By the end of the study period, the hospitals that adopted the universal contact precautions showed a 40% drop in MRSA infections, but no significant change in the spread of VRE. Taken together, the policy therefore did not result in a statistically significant difference between the hospitals that adopted the universal gown and glove procedure compared to the hospitals that did not.

MORE: Outbreak of NIH ‘Superbug’ Provides Valuable Lessons in Protecting Against Disease

But Harris says that shouldn’t discourage hospitals from considering a universal contact precaution for all patients, especially if hospital administrators know there is a high prevalence of MRSA in their community. Not all patients are tested for MRSA before coming into a hospital, and having health care workers wear gowns and gloves while caring for every patient could help to reduce the spread of infections with relatively little cost, he says. “For individual ICUs where [hospital officials] know what the rate of MRSA infections are among ICU patients, or know in the surrounding state what the prevalence of MRSA is, the short answer is yes, we think they should use data like this to make the decision about universal contact precautions,” says Harris.

The fact that the gowns and gloves helped to lower MRSA infections but not VRE cases could have to do with how the bacteria infect patients. MRSA tends to live on the skin, and therefore health care workers could more easily pick up the bacteria on their hands or clothing while seeing patients, while VRE tends to live in the gut. In the study, health care workers who put on gowns and gloves were also more likely to wash their hands after seeing each patient.

MORE: Bacteria Show Up in Hospital Rooms, Again

So given the drop in MRSA infections alone, why wouldn’t hospitals adopt a universal glove and gown policy? Previous studies suggested that requiring people to suit up reduced the number of visits to patients, and therefore led to higher rates of adverse events and complications. But Harris says he and his team did not find such a trend; in fact, patients in the ICUs where workers always wore gowns and gloves had fewer adverse events than those in the control units. “Hopefully that should reassure the public,” he says.

The data, which was published in JAMA and presented at IDWeek 2013, could be helpful as hospitals weigh different options for controlling hospital-acquired infections. Using antiseptics like chlorhexidine or the antibacterial ointment mupirocin can also suppress MRSA and VRE infections, but they can also promote antibiotic resistance. Already VRE cases are concerning since vancomycin is considered the last-resort antibiotic, and resistant bacteria are much harder, if not impossible, to treat. On the other hand, asking health care workers to change gowns and gloves and wash their hands more often doesn’t seem like such a bad idea.