A device used routinely in open chest surgery may have put many more patients at risk of infection from a rare but deadly form of bacteria than earlier believed, according to a study by a Pittsburgh researcher released Wednesday.

The research, released at a national conference of infection prevention experts in Portland, Ore., has prompted at least one local hospital system, Allegheny Health Network, to begin notifying about 3,000 patients who were involved in such surgeries at either Allegheny General Hospital or West Penn Hospital since 2012. UPMC said it is not notifying its patients.

The problem with the device — heater-cooler units that are used to warm or cool patient bodies — has been known since early 2015, after research in European countries first linked infections in patients to contamination in one particular type of unit, the Stockert 3T made by LivaNova of Germany.

U.S. regulators have since found the same problem they suspect led to the infections from the Stockert 3T — cooling fans aerosolizing leaking water — was possible with other manufacturers as well. Almost all of the reported cases of infection have come from the Stockert 3T, but a few have been associated with other manufacturers’ units as well.

The new study by Jack Rihs, head of laboratory services at Special Pathogens Laboratory in the Pittsburgh Bluff neighborhood, found that the rate of contamination in heater-cooler units was much higher than the U.S. Food and Drug Administration believed last fall when it said up to 500,000 people might be at risk.

In samples of water from the units — all of them Stockert 3Ts, which once made up 60 percent of the market in the U.S. — Mr. Rihs found that 33 of 89 of the heater-cooler units he tested from 23 states, the District of Columbia and Canada tested positive for mycobacterium chimaera.

“I was surprised that so many were positive,” Mr. Rihs said, “because [M. chimaera] is such a rare pathogen and to find so many in these devices all over the U.S. is unusual.”

(Excerpt from Pittsburgh Post Gazette)