Usage, residue, and human health risk of antibiotics in Chinese aquaculture: A review.

As the human population increases there is an increasing reliance on aquaculture to supply a safe, reliable, and economic supply of food Although food production is essential for a healthy population, an increasing threat to global human health is antimicrobial resistance Extensive antibiotic resistant strains are now being detected; the spread of these strains could greatly reduce medical treatment options available and increase deaths from previously curable infections Antibiotic resistance is widespread due in part to clinical overuse and misuse; however, the natural processes of horizontal gene transfer and mutation events that allow genetic exchange within microbial populations have been ongoing since ancient times By their nature, aquaculture systems contain high numbers of diverse bacteria, which exist in combination with the current and past use of antibiotics, probiotics, prebiotics, and other treatment regimens—singularly or in combination These systems have been designated as “genetic hotspots” for gene transfer As our reliance on aquaculture grows, it is essential that we identify the sources and sinks of antimicrobial resistance, and monitor and analyse the transfer of antimicrobial resistance between the microbial community, the environment, and the farmed product, in order to better understand the implications to human and environmental health

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The Rising Tide of Antimicrobial Resistance in Aquaculture: Sources, Sinks and Solutions.

Antibiotics bioremediation: Perspectives on its ecotoxicity and resistance.

The greater abundances of antibiotic resistance genes (ARGs) in point-of-use tap and reclaimed water than that in freshly treated water raise the question whether residual disinfectants in distribution systems facilitate the spread of ARGs. This study investigated three widely used disinfectants (free chlorine, chloramine, and hydrogen peroxide) on promoting ARGs transfer within Escherichia coli strains and across genera from Escherichia coli to Salmonella typhimurium. The results demonstrated that subinhibitory concentrations (lower than minimum inhibitory concentrations [MICs]) of these disinfectants, namely 0.1–1 mg/L Cl2 for free chlorine, 0.1–1 mg/L Cl2 for chloramine, and 0.24–3 mg/L H2O2, led to concentration-dependent increases in intragenera conjugative transfer by 3.4–6.4, 1.9–7.5, and 1.4–5.4 folds compared with controls, respectively. By comparison, the intergenera conjugative frequencies were slightly increased by approximately 1.4–2.3 folds compared with controls. However, exposure to disinf...

Subinhibitory Concentrations of Disinfectants Promote the Horizontal Transfer of Multidrug Resistance Genes within and across Genera

Impacts of addition of natural zeolite or a nitrification inhibitor on antibiotic resistance genes during sludge composting.

Environmental antibiotic resistance has drawn increasing attention due to its great threat to human health. In this study, we investigated concentrations of antibiotics (tetracyclines, sulfonamides and (fluoro)quinolones) and abundances of antibiotic resistance genes (ARGs), including tetracycline resistance genes, sulfonamide resistance genes, and plasmid-mediated quinolone resistance genes, and analyzed bacterial community composition in aquaculture environment in Guangdong, China. The concentrations of sulfametoxydiazine, sulfamethazine, sulfamethoxazole, oxytetracycline, chlorotetracycline, doxycycline, ciprofloxacin, norfloxacin, and enrofloxacin were as high as 446 μg kg−1 and 98.6 ng L−1 in sediment and water samples, respectively. The relative abundances (ARG copies/16S ribosomal RNA (rRNA) gene copies) of ARGs (sul1, sul2, sul3, tetM, tetO, tetW, tetS, tetQ, tetX, tetB/P, qepA, oqxA, oqxB, aac(6′)-Ib, and qnrS) were as high as 2.8 × 10−2. The dominant phyla were Proteobacteria, Bacteroidetes, and Firmicutes in sediment samples and Proteobacteria, Actinobacteria and Bacteroidetes in water samples. The genera associated with pathogens were also observed, such as Acinetobacter, Arcobacter, and Clostridium. This study comprehensively investigated antibiotics, ARGs, and bacterial community composition in aquaculture environment in China. The results indicated that fish ponds are reservoirs of ARGs and the presence of potential resistant and pathogen-associated taxonomic groups in fish ponds might imply the potential risk to human health.

Antibiotics, Antibiotic Resistance Genes, and Bacterial Community Composition in Fresh Water Aquaculture Environment in China

The aim of this study was to explore the prevalence of blaCTX-M and elucidate the characteristics of transferable blaCTX-M-55 plasmids.Escherichia coli were isolated from 10 large-scale duck farms from nine counties and cities in Guizhou Province. They were identified, subjected to antimicrobial susceptibility testing and screened for antibiotic resistance genes. blaCTX-M-positive strains were subtyped, and blaCTX-M-55-containing strains were further analysed by multilocus sequence typing, conjugation experiments and polymerase chain reaction-based replicon typing. Three transferable plasmids were selected for whole genome sequencing sequencing and further analysis of genetic context.In total, 128 E. coli strains were identified, and 23 were blaCTX-M-positive. Subtype analysis of blaCTX-M-positive strains revealed that 23 were blaCTX-M-55 and one of the strains contained both blaCTX-M-65 and blaCTX-M-55. They were divided into 12 multilocus sequence typing types, and 6 were undetermined. blaCTX-M-55-bearing plasmids in seven were transferred to E. coli C600 at frequencies between 10-6 and 10-9, and blaCTX-M-55 was found to be located on IncN, IncFⅡ and IncFII-N fusion type plasmids. Three plasmids (IncFⅡ plasmids pEC99_Plas3 and pS1_Plas2 and IncFII-N plasmid pD2_plas2) shared a homologous region of IS26-ARGs-IS26-blaTEM-orf477-blaCTX-M-55-ISEcp1△-IS26.Our study demonstrates the environmental presence of blaCTX-M-55 harbouring E. coli in Guizhou. Analysis of the genetic context of blaCTX-M-55 aids in understanding possible dissemination routes of ESBL genes and controlling widespread antibiotic resistance. 

Yafei Li

Papers

Antibiotics, Antibiotic Resistance Genes, and Bacterial Community Composition in Fresh Water Aquaculture Environment in China

Genetic Context Diversity of Plasmid-Borne blaCTX-M-55 in Escherichia coli Isolated from Waterfowl.

The emergence and molecular study of methicillin-resistant Staphylococcus aureus ST239, ST59, ST9, and ST630 in food animals, Chongqing, China.