8 hours ago
Just one serving of a favorite summer food raises risk of contracting super bacteria resistant to treatments
People indulging in a shrimp cocktail or seafood salad this summer could be at risk of potentially fatal antibiotic-resistant infections, scientists warn.
Researchers in Georgia have found that seafood favorites like shellfish and scallops imported into the US may be contaminated with bacteria that is resistant to colistin, a 'last-resort' medication used to kill bacteria that isn't cleared by other treatments.
And consuming the seafood could lead to the gastrointestinal tract being colonized by the bacteria, experts suggest, which could wait for the immune system to weaken before causing a deadly infection.
It's not known exactly how many strains of bacteria are resistant the drug, but experts are worried that the number is growing amid widespread overuse of antibiotics, allowing bacteria to mutate and become better at evading treatments.
Colistin is only used when standard treatments have failed — typically against pneumonia or sepsis, a life-threatening blood infection.
Scientists have long voiced concern about rising drug resistance, warning it could turn previously treatable infections into life-threatening diseases.
Lead researcher Issmat Kassem, a microbiologist, warned: 'We love our seafood. [But] if you go out to lunch today, your plate might have ingredients from six, seven, eight countries.
'Some countries do not have strict regulations for using antibiotics in food animal production, so imported food can be a vehicle for transmission of resistance.'
Colistin was first discovered in the 1950s but doctors stopped using it by the 1980s because it was revealed patients using the drug were found to suffer from damage to the nerves and kidneys.
However, a rise in drug-resistant infections in the 1990s saw use of the medication increase as there was a need for new treatments.
Data online suggests that colistin is currently administered to fewer than 1,000 seriously ill patients in the US every year, although this number continues to rise.
For the study, researchers tested shrimp and scallops bought from eight seafood markets in Atlanta, Georgia.
The team tested samples for the colistin-resistance genes known as mcr.
At least 10 types of mcr genes have now been identified, with scientists warning they might spread though imported and exported food.
It wasn't clear how the resistant bacteria had ended up on seafood, but previous research has suggested this may happen if rainwater falls on farms and then flows into the waters where the fish or crustaceans are being farmed.
More than 90 percent of seafood consumed in the US is imported, with major sellers including China, Norway, Ecuador, Chile and India.
The food is screened for numerous contaminants, like mercury, PFAS and antibiotics, but is not checked for antibiotic-resistant bacteria.
And each country has varying regulations when it comes to collecting, storing, slaughtering and exporting or importing goods for consumption.
In some countries, farm animals, including farmed seafood, may be treated with colistin, which studies show may marginally boost their growth rates.
A 2023 study suggested that despite concerns over resistance, the antibiotic was still being widely used for feed in some low- and middle-income countries.
It is also given sometimes to prevent outbreaks because of the unsanitary conditions some animals are kept in.
It was not clear what the name of the colistin-resistant bacteria was, or which countries the imported seafood had come from.
The findings were revealed in a presentation for ASM Microbiome 2025 in Los Angeles, the annual meeting of the American Society for Microbiology. It is set to be published as a study in the journal mSphere.
The scientists cautioned that their study focused on just one food group, but said it was likely that others also posed a risk.
The team added that the drug-resistant bacteria they found on the seafood matched a strain they had also detected in wastewater in the city, suggesting the bacteria was spreading in the community.
Antibiotic resistant bacteria are a growing risk in America, with more than 2.8million infections now recorded every year — and with treatment costs having more than doubled since 2002.
Around 35,000 people die from antibiotic-resistant infections in the US every year.
While much of seafood is consumed raw in the summer, people can reduce their risk by cooking the food, which likely kills the resistant bacteria. But Americans should be extra vigilant as the bacteria can still be spread onto the surface food is prepared on — raising the risk of infection.
Older individuals and pregnant women are already advised not to eat raw seafood, especially sushi, which can put them at a higher risk of infection because of their weakened immune systems.
