A plate of fish and chips is increasingly likely to expose people to untreatable bacteria because of the spread of superbugs at sea, research has found.
A study of dolphins revealed a surge in the marine environment of antibiotic-resistant bugs that are dangerous to humans.
Although dolphins are eaten in very few parts of the world, they are seen as a good indicator for the safety of sea life that does end up as food.
Investigators at Florida Atlantic University periodically captured, swabbed then released bottlenose dolphins from 2003 to 2015 in the Indian River Lagoon on the United States Atlantic coast.
Between 2009 and 2015, resistance in various strains of E. coli to common antibiotics more than doubled, while the resistance to drugs of a pathogen called Vibrio alginolyticus, known to cause serious seafood poisoning, also showed a significant rise, they found.
Scientists also found evidence of resistant Acinetobacter baumannii, which is traditionally the cause of serious hospital-acquired infections.
The findings, published in the journal Aquatic Mammals, raise the prospect that people who eat raw or undercooked fish could fall ill with bugs for which there are no useful medicines.
Antimicrobial resistance (AMR) is one of the gravest public health emergencies facing the world, threatening to make common infections deadly for the first time in almost a century.
AMR occurs when the DNA of bacteria mutates, or different types of bacteria acquire DNA from each other, rendering antibiotics ineffective. It has been driven by profligate use of antibiotics in human and animal healthcare and because no new classes of the drugs have been developed in decades.
Adam Schaefer, who led the Florida research, said: "We have been tracking changes over time and have found a significant increase in antibiotic resistance in isolates from these animals.
"This trend mirrors reports from human healthcare settings.
"Based on our findings, it is likely that these isolates from dolphins originated from a source where antibiotics are regularly used, potentially entering the marine environment through human activities or discharges from terrestrial sources."
Over 13 years, the Florida team collected samples containing 733 pathogen isolates from 171 dolphins, and 88 per cent of these isolates were resistant to at least one antibiotic.
The most common resistance, found in 91.6 per cent of isolates, was to the erythromycin antibiotic.
Dr Peter McCarthy, the co-author, described the drug resistance found during the study as a "significant public health concern".
Global health chiefs have warned that an increasing number of tuberculosis strains are becoming resistant to antibiotics.