New York, June 22 (IANS) A team of US researchers on Sunday said it has identified a way that colistin (a potent, last-resort antibiotic) resistance genes are spreading via imported seafood.

Colistin is used only to treat people with dangerous, life-threatening bacterial infections that have developed resistance to other drugs. But it’s not foolproof.

Worldwide, resistance to colistin is spreading, further diminishing treatment options and putting infected people at higher risk.

Researchers from the University of Georgia recently identified a way that colistin resistance genes are spreading.

In a new study, microbiologist Issmat Kassem, and his group have reported the first isolation of colistin-resistance genes in bacteria found in imported shrimp and scallops, purchased from 8 food markets around Atlanta.

“Many people don’t know that most seafood consumed in the U.S. is imported, Kassem said, including about 90 per cent of shrimp.

Imported seafood is screened for contaminants but the process doesn’t catch everything, especially antimicrobial resistance genes. “The bacteria that were carrying colistin resistance genes are not normally screened.”

Kassem and his group also found that some of the resistance genes are carried on plasmids — round bits of genetic material that can be transmitted from bacteria to bacteria.

Antimicrobial resistant infections kill hundreds of thousands of people globally every year, and antimicrobial resistance is a rising public health menace.

Colistin was first introduced in the 1950s to treat infections by pathogenic Gram-negative bacteria, but it takes a heavy toll on patients, including increased risk of damage to the nerves and kidneys.

It was discontinued in the U.S. in the 1980s. However, Kassem noted, other countries continued to use it in agricultural settings, both to treat infections and to promote animal growth.

Colistin was eventually reintroduced to human medicine because it was one of the few options available to treat certain bacterial infections. The World Health Organization categorises colistin as a high priority critically important antibiotic, which means it is an essential option for treating serious human infections.

Researchers cautioned that the group identified 1 source of colistin resistance, but there could be other, and they’re likely spreading.

—IANS

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