September 4, 2017


Fishmeal source of antibiotic resistance genes thriving in marine fish farm sediments



Antibiotic-resistant bacteria and genes for antibiotic resistance have been showing up in unexpected places including isolated caves and ancient permafrost. This time, one team of scientists has surprisingly found these genes-where they can be exchanged among bacteria and possibly end up in the food chain-in the sediment of marine fish farms even when no antibiotics have been applied.


According to the scientific team's report, which appeared in the American Chemical Society's Environmental Science & Technology journal, one suspected source of these bacteria and genes is fishmeal, which is made of low-value fish and seafood byproducts.


Previous research has found that fish food, which generally incorporates fishmeal, can contain antibiotics. But no study had yet measured the abundance of antibiotic resistance genes in the fishmeal.


As millions of tonnes of fishmeal are used every year with much of it sinking uneaten to the ocean floor, lead researcher Jing Wang and colleagues wanted to see what its impact could be on the mariculture "resistome," or collection of resistance genes.


The researchers analysed commercially available fish meal and found 132 antibiotic resistance genes, some of which could potentially confer resistance to common antibiotics and those of last resort, such as vancomycin.


Lab testing showed that the application of fishmeal to marine farm sediment samples changed the makeup of bacteria species, boosting potential human pathogenic bacteria (Vibrio species), which contribute to foodborne illnesses worldwide. It also increased the abundance and diversity of antibiotic resistance genes in the test sediments.


The results suggest that fishmeal product could itself be a reservoir of these bits of DNA and could promote their distribution globally.


The researchers received funding from the National Basic Research Programme of China.