Nature & Environment

Farm-Raised Fish Have Traces of Antibiotics: The Rise of Antibiotic-Resistant Bacteria

Catherine Griffin
First Posted: Oct 21, 2014 09:24 AM EDT

Aquaculture has the potential to be a boon to wild fish populations. Fishing pressures can be partly relieved and allow populations to rebound. That said, there are some issues with farm-raised fish--antibiotics among them. Now, scientists have taken a closer look at the antibiotic content in farm-raised fish.

Antibiotic overuse is a serious issue in today's society. It can lead to the development of resistant microbial strains which, in turn, can pose a threat to global health. Each year, antibiotic-resistant microbes sicken about two million people in the U.S. alone and kill about 23,000 people. That's why regulating antibiotic use is crucial.

"The threat of living in a post-antibiotic era cannot be avoided without revising current practices in the use of antibiotics in animal husbandry, including aquaculture," said Rolf Halden, one of the researchers, in a news release.

In order to see exactly how prevalent antibiotic use is in aquaculture, the scientists examined the persistence of antibiotics in seafood raised by modern aquaculture. More specifically, they looked at 27 seafood samples for the presence of antibiotics. The samples represented five of the top 10 most consumed seafood varieties in the U.S., including shrimp, tilapia, catfish, swai and Atlantic salmon.

So what did they find? It turns out five antibiotics were present in detectable amounts. They found oxytetracycline in wild shrimp, farmed tilapia, farmed salmon and farmed trout. They also found 4-epioxytetracycline in farmed salmon, sulfadimethoxine in farmed shrimp, ormetoprim in farmed salmon and virginiamycin in farmed salmon that had been marketed as antibiotic-free.

While all of the seafood analyzed was in compliance with FDA regulation, sub-regulatory antibiotic levels have the potential to promote antibiotic resistance development. In addition, the use of antibiotics can be disseminated to the surrounding environment, and there may be high antibiotic exposure for personnel working in aquaculture facilities.

The findings reveal that some changes in aquaculture may be needed to ensure that practices can be carried out on a large scale in a sustainable manner. Not only that, but they show that antibiotics present at levels well below regulatory limits can still promote the development of drug-resistant microorganisms.

The findings are published in the Journal of Hazardous Materials.

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