Los Angeles County reported about 350 cases of carbapenem-resistant Klebsiella pneumoniae between June and December 2010, ABC News reported Friday.
"These patients tend to be elderly, they are commonly on ventilators and they often stay at the facility for an extended period of time," said Dr. Dawn Terashita, medical epidemiologist and lead author of the study from the Los Angeles County Department of Public Health.
CRKP and other superbugs such as methicillin-resistant Staphylococcus aureus are proving resistant to typical antibiotics.
"We develop new drugs to defeat the infections, and germs change to get around those drugs and this is one of those cases," Dr. Richard Besser, ABC News chief health and medical editor, said.
"It's like an arms race and in many ways the germs are winning," he said.
While not new to California, CRKP is a newer infection than MRSA, Dr. Arjun Srinivasan of the Centers for Disease Control and Prevention said.
"But in terms of mortality and morbidity, it's very, very serious," Srinivasan said. "These infections are more difficult to treat than MRSA."
"This superbug is very dangerous," Besser said. "It tends to affect people that are in the hospital for long periods of time; people that have underlying medical problems; people who have been in nursing homes."
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