The gene spreads readily among bacteria, and it could make these multi-drug resistant strains almost impossible to treat. Nor have any links been identified between human cases and instances in which the gene has been found in pigs in a slaughterhouse in Illinois and another in South Carolina, he said.
The CDC on Friday also released new details about the Pennsylvania woman's case, the first reported time the superbug gene had been found in the United States.
Investigators said they don't know how she got the superbug.
The girl had traveled to the Caribbean for about two weeks to visit friends and relatives.
While she was there, she ate chicken and goat meat from a live animal market.
The girl recovered fully, and the bacteria did not spread to anyone else in her family or to health-care providers she came in contact with.
Officials, however, expect more cases to surface in the United States, and on Friday recommended increased surveillance for bacteria that show resistance to colistin.
[The superbug that doctors have been dreading just reached the U.
S.] Food has been the most common way humans have acquired this superbug in other places, and the Connecticut case suggests that food is also a possible cause, said Maroya Walters, a CDC epidemiologist.
The gene allows the organism to withstand the antibiotic colistin, the drug doctors use to treat patients who have infections that don’t respond to other antibiotics.