Sulfonamide resistance evaluation in five animal species and first report of sul4 in companion animals.

Sulfonamides are one of the oldest groups of antibacterial agents with a broad-spectrum, used as first line treatment in bacterial infections. Their widespread use produced a selective pressure on bacteria, as observed by the high incidence of sulfonamides resistance mainly in Gram negative bacteria isolated from animals. In this research, the presence of sulfonamide resistance genes (sul1, sul2, sul3, and sul4) in phenotypically resistant Escherichia coli isolates has been studied. These genes were amplified in isolates recovered from five animal species, with different interactions to humans: cattle, swine, poultry as livestock, and dogs and cats as companion animals. Isolates were collected according to their phenotypic resistance, and the magnetic bead-based Luminex technology was applied to simultaneously detect sul target genes. The frequency of sul genes was highest in swine, among livestock isolates. The sul1 and sul2 were the most frequently sulfonamide resistance genes detected in all phenotypically resistant isolates. Notably, in companion animals, with a closest interaction with human, sul4 gene was detected. To our knowledge, this is the first report of the presence of sul4 gene in E. coli collected from animals, whereas previously the presence of this gene was reported in environmental, municipal wastewater and human clinical isolates. These results highlighted the importance of continuous antimicrobial resistant genes monitoring in animal species, with a special care to companion animals.

Effects of corresponding and non-corresponding contaminants on the fate of sulfonamide and quinolone resistance genes in the Laizhou Bay, China.

The environmental behaviors and migration patterns of antibiotic resistance genes (ARGs) have attracted considerable research interest. However, there has been little research concerning the effects of corresponding and non-corresponding contaminants on the fate of ARGs in coastal environments. In the present study, the distribution of intI1, sul1, sul2, qnrS and aac(6')-Ib were analyzed in water and sediment samples of Laizhou Bay in the context of corresponding and non-corresponding contaminants. The abundance of intI1, sul1 and sul2 genes exhibited a clear decreasing trend extending from the inner estuary to the coastal area. Strong and positive correlations existed between sul1/sul2 and sulfonamide antibiotic residues in sediments, and between the abundances of intI1 and sul1/sul2. Statistical analyses indicated that non-corresponding contaminants were partially correlated with ARG abundances. These results suggest that non-corresponding contaminants may have direct or indirect influences on the abundances of ARGs and intI1 in the Laizhou Bay.

Persistence and risk of antibiotic residues and antibiotic resistance genes in major mariculture sites in Southeast China.

Antibiotics are widely used in mariculture industry, and this study attempts to determine the extent of water and sediment pollution by antibiotic residues in 13 major mariculture sites in China. Through chemical and molecular biology analysis, the results showed that the total concentrations of sulfonamides and tetracyclines were in the range 62.0-373.8ngL-1 and 0.2-259.1ngL-1 respectively in water samples, and in the range 0.19-1.59ngg-1 dry weight and 3.45-74.84ngg-1 dry weight respectively, in sediments samples. The occurrence of antibiotic resistance genes (ARGs) was detected in all sites. Compared with the tetracyclines resistance genes, the absolute copy number and relative abundance of the sulfonamides resistance genes were 4.3 times and 2.3 times higher in water and sediment from the mariculture sites, with the dominant resistance genes being sul2. The abundance of sul3 in the water phase was significantly correlated with the concentrations of sulfamerazine, while the abundance of sul2 in the sediment phase was significantly with sulfadiazine concentrations. The abundance of tetM in the sediment phase was significantly correlated with the concentrations of oxytetracycline. The findings demonstrate the persistence of antibiotic residues and ARGs in major mariculture sites in Southeast China.