The Impact of intensive fish farming on the resistome of pond sediment and fish gut microbiota

Abstract

Aquaculture is a fast-growing animal food sector, and freshwater fish farming is particularly common in Central and Eastern Europe. As the biodiversity of fishery ponds is changed towards fulfilling the industrial needs, precautions should be taken to keep the system sustainable and protect the adjacent environment from possible damage. Due to risk of infectious diseases, antibiotics are used in aquaculture production systems. The constant exposure to antimicrobials can contribute to the rise of antibiotic resistance in aquaculture products and the adjacent ecosystems, with possibility of dissemination to the wider environment as well as between animals and humans. Even though previous studies have found antibiotic resistance genes in the sediments and water of farming ponds, the tendency and direction of spreading is not clear yet. The objective of this project is to evaluate the influence of intensive fish farming on the water bodies used for the aquaculture and in the surrounding environment, concentrating on the possibility of spread of clinically important antibiotic resistance genes (ARGs). The comparison of ARGs composition in the sediments of the fishery ponds (and the water bodies both upstream and downstream) as well as fish gut contents could show the impact of the aquaculture on the surrounding water ecosystems as well as the possibility of transferring the antibiotic resistance genes to the human hosts. Our results show, that ARGs were detected in all the sediment samples, including the samples taken from the lake upstream from the fishery ponds. The spread of ARGs in the sediment samples was comparable in all water bodies tested, indicating the ARGs detected likely belong to bacteria naturally inhabiting the sediments. However, when the contents of fish gut were tested for ARGs content, a tendency of higher ARGs numbers was observed in the samples from the fishery ponds and the lake downstream. This indicates that the treatment of the fish in the fishery ponds could influence the microbiota of the fish gut and could cause its shift towards higher antibiotic resistance.