POWELTON (WPVI) --Penn Medicine is contacting patients who may have been exposed to a dangerous bacteria during heart surgery.
This comes after four patients at Penn Presbyterian Medical Center were reported to have been infected, possibly from equipment used during heart surgery.
The bacteria is called non-tuberculous mycobacteria, better known as NTM.
It is commonly found in soil and water, however, infectious are rare.
They tend to occur more frequently in women, older people, and those with suppressed immune systems.
The FDA had warned hospitals there may be a link between the bacteria and heater-cooler machines used to warm or cool blood during surgery.
The agency says they can spread NTM in the air.
21 patients at three Pennsylvania hospitals - Penn Presby, Hershey Medical Center, and Wellspan York Hospital - have been diagnosed with it over the past two years.
Some patients have died, but because of the fragile nature of many cardiac patients, it's not certain whether NTM caused the deaths.
In a statement, Susan Phillips, a spokesperson for Penn Medicine, said, "Following the identification, across the U.S. and Europe, of a link between NTM, or nontuberculous mycobacteria and a specific machine that helps support the heart and lungs during major surgeries, we removed this equipment from use in all of our hospitals."
Phillips says the machine was used for less than one half of one percent of the heart surgery patients, so it's believed the risk to other patients is minimal.
However, the hospital will be contacting a broader number of heart patients, to offer them information, and it needed, evaluations for those patients.