Abstract
Persistence and dispersal of antibiotic resistance genes (ARGs) are important factors for assessing ARG risk in aquaculture environments. Here, we quantitatively detected ARGs for sulphonamides (sul1 and sul2) and trimethoprim (dfrA1) and an integrase gene for a class 1 integron (intI1) at aquaculture facilities in the northern Baltic Sea, Finland. The ARGs persisted in sediments below fish farms at very low antibiotic concentrations during the 6-year observation period from 2006 to 2012. Although the ARGs persisted in the farm sediments, they were less prevalent in the surrounding sediments. The copy numbers between the sul1 and intI1 genes were significantly correlated suggesting that class 1 integrons may play a role in the prevalence of sul1 in the farm sediments through horizontal gene transfer. In conclusion, the presence of ARGs may limit the effectiveness of antibiotics in treating fish illnesses, thereby causing a potential risk to the aquaculture industry. However, the restricted presence of ARGs at the farms is unlikely to cause serious effects in the northern Baltic Sea sediment environments around the farms.
Highlights
Aquaculture production is increasing worldwide as a source of fish for human consumption
The detection of trimethoprim resistance genes, sulphonamide resistance genes, florfenicol resistance gene and an integrase gene of class 1 integrons was done for six sediment samples chosen from northern Baltic Sea fish farm sites, using standard PCR
Our results showed that the sulphonamide resistance genes and trimethoprim resistance gene were persistent in the Baltic Sea farm sediments during the 6-year observation period
Summary
Aquaculture production is increasing worldwide as a source of fish for human consumption. The prophylactic and therapeutic use of antibiotics results in the occurrence of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs) in the aquaculture environment [1,2]. This may lead to seawater and the sediment becoming reservoirs for ARGs [3]. The ARGs in aquaculture environments can be transferred horizontally among microbes and be transferred to fish pathogens [4]. The presence of ARGs in aquaculture environments may lead to inefficiency in treating fish diseases using antibiotics [5]. To avoid production losses in the fish-farming industry, it is important to control the occurrence and spread of ARGs in aquaculture facilities
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