New York– A new U.S. study has identified imported seafood as a previously underrecognized source of colistin resistance — a worrying development involving one of the world’s last-resort antibiotics.
Researchers from the University of Georgia, led by microbiologist Issmat Kassem, have reported the first-ever detection of colistin resistance genes in bacteria found in imported shrimp and scallops sold at food markets in the Atlanta area.
Colistin is used only in the most critical cases of bacterial infections that are resistant to other drugs. Despite its importance, resistance to colistin is spreading worldwide, leaving doctors with fewer treatment options for life-threatening infections.
“Most people don’t realize that around 90% of the shrimp consumed in the U.S. is imported,” said Kassem. “While seafood is screened for contaminants, it’s not typically checked for antimicrobial resistance genes. That leaves a dangerous blind spot.”
In their study, Kassem’s team discovered that the colistin resistance genes were not just present, but in some cases carried on plasmids—small, circular strands of DNA that bacteria can easily exchange. This makes the genes highly mobile and capable of spreading rapidly across different bacterial populations.
Antimicrobial resistance is already a major public health crisis, causing hundreds of thousands of deaths annually. Colistin, which was introduced in the 1950s and withdrawn in the U.S. in the 1980s due to its toxicity, has been reintroduced in recent years because of its effectiveness against multi-drug resistant infections.
However, widespread agricultural use of colistin in some countries — both for animal treatment and growth promotion — has contributed to the rise in resistant bacteria, some of which now appear to be entering global food supply chains.
The World Health Organization classifies colistin as a “high priority critically important antibiotic” due to its role in treating the most severe infections. The emergence of resistance in foodborne bacteria is especially concerning, given how easily such genes can be transmitted.
Researchers caution that while seafood is now confirmed as one route of colistin resistance gene transmission, other sources are likely contributing as well.
“This is just one pathway,” Kassem warned. “There are likely more. And they’re spreading.” (Source: IANS)
