White Memorial Medical Center shut down the neonatal unit on Dec. 4 following an outbreak of Pseudomonas aeruginosa, hospital officials said Friday.
The germ is believed to have infected five babies in the unit since it was detected on Nov. 30, said Dr. Laurene Mascola, director of the county's acute communicable disease control unit. One of the infants died, likely because of the pathogen, she said.
All infants who tested negative for the germ are being held in separate areas, officials said.
"These are very, very sick babies to begin with. (An infection) can increase their chance of dying," Mascola said.
On Friday, the hospital shuttered the pediatrics intensive care ward after discovering the bacterium had infected an infant and a toddler there, Dr. Rosalio Lopez, the hospital's chief medical officer, said in a statement.
Officials say they've identified the source of the outbreak — a medical instrument called a laryngoscope blade used to look at an infant's larynx that may not have been properly cleaned. Officials don't believe there is a danger to other babies, Lopez said.
Though common, the germ is particularly virulent in those with weak immune systems such as newborns who are premature or critically ill.
The hospital is working with county, state and federal health officials to investigate the outbreak, Lopez said.