Three patients who underwent heart surgery at Penn Presbyterian Medical Center in Philadelphia are being treated for nontuberculous mycobacterium infections contracted from contaminated heater-cooler machines used during the surgery. A fourth patient tested positive for the bacteria, but has not displayed signs of infection. According The Philadelphia Inquirer, the addition of the three patients brings the total of such infections in the state of Pennsylvania to 20.
Because of these infections, Penn Medicine is sending letters this month to hundreds of patients who may have been exposed to contaminated heater-cooler machines during major cardiac surgery.
NTM can often be found in tap water and soil and pose little risk to healthy people. While benign in the environment, the microbes can incite infections in ill patients with open chest cavities. The bacteria also grow slowly, delaying symptoms of infection, but the infection is treatable.
"It can take years for them to develop," Sharon Watkins, PhD, an epidemiologist with the Pennsylvania Department of Health, told the Inquirer.
Heater-cooler machines are used during open-heart surgery and use circulating water to modulate body temperature. The devices were previously thought safe because the water never comes into direct contact with the patient's blood. Infectious disease experts now believe small amounts of water can become aerosolized and emit via a vent in the device. The machines can also be very difficult to clean once contamination is detected — the bacteria form a biofilm that is resilient against typical disinfectants.
"Once it's [the bacteria] in there," Patrick J. Brennan, MD, CMO of the University of Pennsylvania health system. told the Inquirer, "it does not appear to be possible to get it out."
Heater-cooler machines have been implicated in other NTM infections recently. For instance, in October 2015, WellSpan York (Pa.) Hospital began notifying approximately 1,300 open-heart surgery patients of potential exposure to NTM from heater-cooler machines, and Penn State Hershey Medical Center did the same.
In fact the Food and Drug Administration issued a safety communication about the devices in October last year, and the CDC issued interim practical guidance on the heater-cooler machines.
The devices may also house other bacteria. On Sept. 19, University of Washington Medical Center in Seattle announced three of its heater-cooler machines tested positive for Legionella bacteria. The bacteria was previously detected in the hospital's water supply and has incited four cases of Legionnaires' disease — a form of pneumonia — in hospital patients. Two of the infected patients have died.
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