Co-proliferation of antimicrobial resistance genes in tilapia farming ponds associated with use of antimicrobials

Abstract

The prevalence of antimicrobial resistance genes (ARGs) in aquaculture has raised serious public concerns for food safety and human health, but its relationships to the use of antimicrobials in aquacultural ponds and even to their residues in the whole aquatic environment remain unclear. In this study, a better coverage of 323 target ARGs and 40 mobile genetic elements (MGEs) was analyzed in sediment using a smart chip-based high-throughput quantitative PCR approach (HT-qPCR) in random 20 ponds of a tilapia farming base in southern China, whose antimicrobial residues were reported previously. In total, 159 ARGs and 29 MGEs were quantified in 58 surface sediment samples across the ponds. Absolute abundance of ARGs ranged from 0.2 to 13.5 × 10⁶ copies g^-1, dominated by the categories of multidrug and sulfonamides. The quantified ARGs abundance and the antimicrobial compound residues were significantly correlated instead with the antimicrobial categories, mainly compounds in categories of fluoroquinolones and sulfonamides and trimethoprim (TMP). Antimicrobial residues alone explained 30.6 % of the ARGs' variation quantified in sediment across the ponds, indicating the clear link between antimicrobials and the proliferation of ARGs in aquaculture. Co-proliferation of the ARGs with non-related antimicrobial compounds quantified in sediment was also observed, especially for aminoglycosides' ARGs, which were highly associated with integrons (intI 1) as argued being carried by the intI 1 gene cassette arrays. Physicochemical properties of sediment (pH, electric conductivity, and total sulfur content) highly contributed the variations of the quantified ARGs abundance (21 %) across all the sediment samples equaling to the MGEs (20 %), suggesting co-selection for ARGs' proliferation in the aquaculture environment. This study provides insights into the interactions between residual antimicrobials and ARGs, which would enhance the understandings on the use and management of antimicrobials in aquaculture worldwide to strategize mitigation of antimicrobial resistance in aquaculture.

Keywords: Antimicrobial resistance genes (ARGs); Mobile genetic elements (MGEs); Physicochemical property; Residual antimicrobials; Sediment; tilapia farming.