Selective pressure of antibiotics on ARGs and bacterial communities in manure-polluted freshwater-sediment microcosms.

Wenguang Xiong,Xueyao Ding,Yongxue Sun,Zhenling Zeng,Mianzhi Wang

doi:10.3389/fmicb.2015.00194

Wenguang Xiong, Xueyao Ding + Show 3 more

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https://doi.org/10.3389/fmicb.2015.00194

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Abstract

The aim of this study was to investigate selective pressure of antibiotics on antibiotic resistance genes (ARGs) and bacterial communities in manure-polluted aquatic environment. Three treatment groups were set up in freshwater-sediment microcosms: tetracyclines group, sulfonamides group and fluoroquinolones group. Sediment and water samples were collected on day 14 after treatment. Antibiotic concentrations, ARGs abundances and bacterial community composition were analyzed. Antibiotic concentrations were determined by ultra-performance liquid chromatography-electrospray tandem mass spectrometry. ARGs abundances were quantified by real time quantitative PCR. Bacterial community composition was analyzed based on amplicon sequencing. Of the three classes of antibiotics analyzed in the treatment groups, accumulation amounts were tetracyclines> fluoroquinolone> sulfonamides in the sediment samples, while they were sulfonamides> fluoroquinolone> tetracyclines in the water samples. In the treatment groups, the relative abundances of some tet resistance genes [tet(W) and tet(X)] and plasmid-mediated quinolone resistance (PMQR) genes [oqx(B) and aac(6′)-Ib] in sediment samples were significantly higher than those in the paired water samples. Tetracyclines significantly selected the bacterial classes including Gammaproteobacteria, Clostridia, and the genera including Salmonella, Escherichia/Shigella, Clostridium, Stenotrophomonas in sediment samples. The significant selection on bacterial communities posed by sulfonamides and fluoroquinolones was also observed. The results indicated that sediment may supply an ideal setting for maintenance and persistence of tet resistance genes [tet(W) and tet(X)] and PMQR genes [oqx(B) and aac(6′)-Ib] under antibiotic pollution. The results also highlighted that antibiotics significantly selected specific bacterial communities including the taxa associated with opportunistic pathogens.

Highlights

Antibiotic resistance genes (ARGs) in the environment are of great concern, since they can be acquired by human commensal bacteria and clinical pathogens
Of sediment samples analyzed in this study, the concentrations of individual tetracycline and fluoroquinolone in the treatment groups were 89–440 and 250–331 fold of those in the control group, while the concentrations of individual sulfonamide in the treatment group were 8–17 fold of those in the control group
Of water samples analyzed in this study, the concentrations of individual tetracycline and fluoroquinolone in the treatment groups were 0.6–8.1 and 5.9–38 fold of those in the control group, while the concentrations of individual sulfonamide in the sulfonamides group were 246-2630 fold of those in the control group

Summary

Introduction

Antibiotic resistance genes (ARGs) in the environment are of great concern, since they can be acquired by human commensal bacteria and clinical pathogens. Persistence and spread of Pressure on ARGs and bacteria environmental ARGs can be promoted by animal production activities (Li et al, 2012; Zhu et al, 2013). Large amounts of various antibiotics have been widely used for disease prevention, disease treatment and growth promotion in animal feedlots. The production of antibiotics used in animal feedlots was approximately 9200 tons in the USA in 2003 (Arikan et al, 2007), and about 6000 tons of veterinary antibiotics was used annually in China (Zhao et al, 2010). Antibiotics discharged from animal feedlots promote the emergence and spread of environmental ARGs (Li et al, 2012)

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