More than one-third of heater-cooler devices sampled during a recent study were contaminated with Mycobacterium chimaera, researchers said, highlighting the risk of the machines to cause nosocomial infections.

M. chimaera is a slow-growing species of nontuberculosis mycobacteria (NTM) commonly found in soil and water, according to the CDC. It rarely makes people sick but can cause fatal postsurgical infections that are often difficult to diagnose, researchers have said.