A drug-resistant bacterium that has surfaced in Southern California has mostly spread in nursing homes, not hospitals, but more needs to be done to track it, health officials said Thursday.

More than 350 cases of Carbapenem-Resistant Klebsiella pneumoniae, or CRKP, have been reported at healthcare facilities in Los Angeles County, mostly among elderly patients at skilled-nursing and long-term care facilities, according to a study by Dr. Dawn Terashita, an epidemiologist with the Los Angeles County Department of Public Health.

"They've been brought into the hospital from the nursing home," said Dr. Brad Spellberg, an infectious-disease expert at the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center near Torrance. "There's no evidence that this organism is being spread person to person in hospitals."

A spokeswoman for the Sacramento-based California Assn. of Healthcare Facilities, which represents more than 1,200 nursing homes, disagreed.

“There’s no evidence this is being spread person to person in nursing homes,” said spokeswoman Deborah Pacyna. “If this was a problem, we would have heard about it.”

At least five patients at Torrance Memorial Medical Center developed CRKP infections during the last year after being transferred to the hospital from nursing homes where they had become infected, said Elizabeth Clark, director of infection control at the hospital.

Once the infections were detected at the hospital, the patients were isolated in private rooms with added safety precautions, Clark said. None of them died or passed on the infection to others, she said.

Clark said CRKP is only one of the drug-resistant infections she battles at the hospital, but that, "it's a concern because of the difficulty of treating someone."