LOS ANGELES—A heart surgeon at Cedars-Sinai Medical Center unwittingly infected five patients during valve replacement surgeries earlier this year, causing four of the patients to need a second operation.

The infections occurred after tiny tears in the latex surgical gloves routinely worn by the doctor allowed bacteria from a skininflammation on his hand to pass into the patients’ hearts, according to the hospital. The patients survived the second operation and are still recovering, hospital officials said.

The outbreak led to investigations by the hospital and both the L.A. County and California departments of public health. The federal Centers for Disease Control and Prevention was also consulted.