New York: A new study by researchers from the University of Georgia has uncovered a troubling pathway for the spread of antibiotic resistance: imported seafood.
The research team, led by microbiologist Dr. Issmat Kassem, discovered genes that make bacteria resistant to colistin—a last-resort antibiotic—present in bacteria found in shrimp and scallops imported to the United States. These seafood samples were collected from eight food markets in and around Atlanta.
Colistin is considered a critical antibiotic, reserved only for treating the most severe, drug-resistant infections when other treatments have failed. However, resistance to colistin is growing globally, leaving doctors with fewer options to fight life-threatening infections.
“Many people don’t realize that around 90 percent of shrimp consumed in the U.S. is imported,” said Dr. Kassem. While imported seafood is typically screened for contaminants, it’s not always checked for antimicrobial resistance genes, which can quietly slip through undetected.
What makes the discovery even more concerning is that some of the resistance genes found in the bacteria are located on plasmids. Plasmids are small, circular pieces of genetic material that can easily transfer between different bacteria. This means that even harmless bacteria in seafood could pass resistance traits to dangerous pathogens.
The use of colistin dates back to the 1950s, primarily for treating infections caused by Gram-negative bacteria. However, due to its harsh side effects—such as kidney and nerve damage—it was phased out in the U.S. in the 1980s. It continued to be used in agriculture in other countries, both to treat animals and promote growth. Colistin was later brought back into human medicine because few other drugs remained effective against some resistant bacteria.
The World Health Organization now classifies colistin as a “high priority critically important” antibiotic due to its essential role in treating severe infections.
The researchers caution that while they’ve identified one source of colistin resistance in imported seafood, there are likely others. The findings highlight the urgent need for better monitoring of antimicrobial resistance in the global food supply.