A total of 132 unique antibiotic resistance genes (ARG) and 4 mobile genetic elements (MGEs) were detected in five fishmeal products. ARG abundance and diversity in the mariculture microcosm sediment were significantly increased by the addition of fishmeal, and trends in ARG patterns correlated with the resident bacterial community in sediment.
Antibiotic-resistant bacteria and genes for resistance had been increased to unexpected levels. Genes for antibiotic resistance arising in different environments and their risks to human health were not clear.
However, a research team had found that the resistance genes were getting into ocean sediments through food for marine fisheries. The study findings were published in ACS' Environmental Science & Technology.
Many disease-causing bacteria have developed resistance to common antibiotics and drugs of the last choice. To reduce the risk to public health, the researchers were finding the way through which resistance genes spread among bacteria.
Even if antibiotics have not been applied, the sediment in marine fish farms harbour antibiotic resistance genes where they could be exchanged among bacteria and might end up in the food chain, the study reported.
Fishmeal that made of low-value fish and seafood by-products could be the source. Earlier, the scientists had found that fish food (fishmeal) could have antibiotics. However, the abundance of antibiotic resistance genes in the fishmeal is not yet measured.
Yearly, millions of tons of fishmeal are being used with much of it sinking uneaten to the ocean floor. Jing Wang and colleagues wanted to understand its impact on the mariculture "resistome," or collection of resistance genes.
After examining the commercially available fish meal, the research team had found 132 antibiotic resistance genes. Some of the genes could potentially confer resistance to common antibiotics and those of the last choice, such as vancomycin.
In lab testing, the team applied fishmeal to marine farm sediment samples and revealed that the application changed the bacteria species, boosting potential human pathogenic bacteria i.e., Vibrio species that contribute to foodborne illnesses globally.
The application also increased the abundance and diversity of antibiotic resistance genes. The study findings showed that fishmeal product could itself be a reservoir of the antibiotic resistance genes (ARGs) and could spread them globally.
The study has revealed for the first time that fishmeal itself is a major reservoir for ARGs and the shift in the bacterial community induced by the nutrients in fishmeal is the main driver shaping the resistome in mariculture microcosm sediment.