Three patients who underwent heart surgery at Penn Presbyterian Medical Center contracted unusual infections linked to a medical device called a heater-cooler, bringing the total of such cases in Pennsylvania to at least 20.
A fourth patient at Penn Presbyterian tested positive for the type of bacteria in question but did not show signs of infection, said Patrick J. Brennan, chief medical officer of the University of Pennsylvania health system.
Three of the four patients remain under the care of Penn physicians and are "doing well," while the fourth was treated at another hospital, Brennan said. Elsewhere, similar infections have been linked to patient deaths.
Heater-coolers have been in widespread use for decades to heat or cool the blood of patients on a heart-lung bypass machine, needed for procedures such as open-heart surgery. The temperature is modulated by means of circulating water that does not come into contact with the patient's blood, so the device was not thought to pose a risk of infection.
Infectious-disease experts now say otherwise, because small amounts of water can become aerosolized and escape through a vent in the device.
The microbes causing the infections, called mycobacteria, often are present in tap water and soil. They pose no risk to healthy people, but for a gravely ill patient whose chest cavity is opened for surgery, the bacteria can spell trouble.
Further complicating the picture, these microbes grow very slowly. They do not lead to symptoms for many months, so the field of medicine was initially slow to link infections to the heater-cooler devices.
"It can take years for them to develop," said epidemiologist Sharon Watkins, of the state Department of Health.
In Seattle this week, physicians reported that the devices may pose yet another kind of infectious threat. At the University of Washington Medical Center, an investigation found that heater-coolers were contaminated with bacteria that cause Legionnaires' disease.
The mycobacteria infections in Pennsylvania were first reported in October at WellSpan York Hospital and in November at Penn State Hershey Medical Center. Additional cases have since come to light, for a total of 12 at York and five at Penn State Hershey, the hospitals said.
New Jersey health officials said Tuesday that while they had not confirmed any such infections, they do "have one possible case that is currently under investigation,'' Health Department spokeswoman Donna Leusner wrote in an email.
Penn Presbyterian identified its four cases after the state Health Department urged all Pennsylvania hospitals to look through their records to find other possible infections in patients who were placed on a bypass machine. Two of the four cases came to light just in the last month, said Penn Medicine's Brennan.
Hospitals have rushed to respond in different ways to the emerging threat, as the machines are essential to performing a variety of lifesaving surgeries. Some hospitals have used only sterilized or filtered water in the devices, at the recommendation of the Food and Drug Administration.
After one study suggested the contamination might have been present in the devices at the point of manufacture, Penn Medicine took the extra step of replacing all of its heater-coolers with new ones, Brennan said.
He said the design of the new devices, made by a company called CardioQuip, makes them less prone to bacterial contamination.
But even those devices may not be immune, said biomedical engineer Lawrence Muscarella, an infection-control consultant based in Montgomeryville. The same company made the Seattle devices found to be contaminated with the bacteria that cause Legionnaire's disease, according to the Seattle Times.
"I think this is yet another wake-up call," Muscarella said. "This is a national problem."
A spokesman for CardioQuip said there is no evidence that its devices can aerosolize waterborne bacteria, or that its devices contributed to any infections at the hospital in Washington.
Brennan said that once contaminated, its previous heater-cooler devices were extremely hard to clean. The bacteria can form a slimelike "biofilm" that does not yield to standard disinfectants.
"Once it's in there," Brennan said, "it does not appear to be possible to get it out."
Also this month, Penn is sending out letters to several hundred patients who underwent major cardiac surgery while connected to one of the old heater-coolers that tested positive for the type of bacteria in question, said Susan E. Phillips, a senior vice president for the health system. The letters state that the risk of infection is low but that patients should be on the lookout for any symptoms.