Those hands-free electronic water faucets that seem to be in every public bathroom may not be that great at keeping us germ free after all.

A study of newly installed fixtures at Johns Hopkins Hospital showed the faucets were more likely to be contaminated with a common and hazardous bacteria than the old fashioned faucets with separate handles for hot and cold water.

“Newer is not necessarily better when it comes to infection control in hospitals, especially when it comes to warding off potential hazards from water-borne bacteria, such as Legionella species,” Dr. Lisa Maragakis, senior study investigator, said in a statement. “New devices, even faucets, however well intentioned in their make-up and purpose, have the potential for unintended consequences, which is why constant surveillance is needed.”

The new faucets did cut daily water use by more than half, said Maragakis, director of hospital epidemiology and infection control at Hopkins Hospital and an assistant professor at the Johns Hopkins University School of Medicine. But, for example, they also had Legionella growing in half of the water samples from 20 faucets near patient rooms. That compares with 15 percent of the cultures from 20 of the old faucets in the same patient care areas.

Legionella isn’t harmful to most people, but can sicken those with compromised immune systems in hospitals. The Hopkins researchers had aimed to determine how often the new faucets had to be treated to protect vulnerable patients when they discovered the higher rates of bacteria. They’ve notified other hospitals and plan to work with manufacturers to remedy the problem.

Researchers aren't completely sure why there is higher bacterial growth in the new faucets, but it may be because standard water disinfection methods at the hospital didn’t work well on the complex components. They may have more surface area for bacteria to grow.

The finding will be presented April 2 at the Society for Health Care Epidemiology’s annual meeting.