Abundance of Sulfonamide-resistant Bacteria and Their Resistance Genes in Integrated Aquaculture-agriculture Ponds, North Vietnam

Abstract

The use of antibiotics in livestock production is a potential source of antibiotic contamination, which may increase the presence of antibioticresistant bacteria in the aquatic environment. Antibiotic resistance genes can be spread via the food web and through hydrologic processes to human pathogens. We examined the abundance of sulfonamide-resistant (SR) bacteria and their resistance genes in water samples from integrated aquacultureagriculture (VAC) sites. Among the VAC sites investigated, all were contaminated by sulfonamides with varying concentrations and all showed the presence of sulfamethoxazole resistant bacteria (SMXr). Farms rearing pig and duck (pig+duck VAC) showed high contamination with sulfamethazine. SMXr in other sites were less than that in the pig+duck VAC. The SR genes, sul1, sul2 and sul3, were detected from SR isolates with 45–95%. The prevalence of each gene was sul1 (50%), sul2 (21.17%) and sul3 (4.17%). SR isolates possessing plural sul genes belonged to eight genera (Bacillus, Terrabacter, Agrococcus, Enterobacter, Escherichia, Acinetobacter, Dietzia and Shigella). The present study revealed that SR bacteria were distributed in various bacterial groups, including potential human pathogens. This report suggests that the aquatic environment is a reservoir of sul genes, in which the genes may be transferred among not only aquatic bacteria but also human related bacteria.