Abundance and Diversity of Tetracycline Resistance Genes in Soils Adjacent to Representative Swine Feedlots in China

Abstract

Tetracyclines are commonly used antibiotics in the swine industry for disease treatment and growth promotion. Tetracycline resistance was determined in soils sampled from farmlands in the vicinity of nine swine farms located in three cities in China. Totally, 15 tetracycline resistance (tet) genes were commonly detected in soil samples, including seven efflux pump genes (tetA, tetC, tetE, tetG, tetK, tetL, tetA/P), seven ribosomal protection proteins (RPPs) genes (tetM, tetO, tetQ, tetS, tetT, tetW, tetB/ P), and one enzymatic modification gene (tetX). The quantitative real-time PCR was further used to quantify five RPPs genes (tetM, tetO, tetQ, tetW, tetT) and 16S rRNA gene abundances. The concentrations of total tetracyclines (5 typical tetracyclines and 10 of their degradation products) in these soils were measured using liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) and were found to range from 5.4 to 377.8 µg · kg -1 dry soil. Bivariate correlation analysis confirmed that absolute tet gene copies (sum of tetM, tetO, tetQ, tetW genes) were strongly correlated with the concentrations of tetracycline residues (r 2 ) 0.45, P < 0.05), ambient bacterial 16S-rRNA gene copies in each soil sample (r 2 ) 0.65, P < 0.01), and organic matter in soil (r 2 ) 0.46, P < 0.05), respectively. Finally, the phylogenetic analysis on tetM combined with cultureindependent molecular techniques revealed at least five genotypes of tetM in nine soil samples.

Antibiotic resistance genes in manure-amended soil and vegetables at harvest

“…In addition, no significant correlation was found between antibiotics and ARGs, except tetracycline and tetL. It was still inconclusive regarding the relationship between antibiotics and ARGs [34,43]. Previous study had confirmed that quinolone could stimulate the SOS response (e.g, 0.05 mg ml −1 CIP was strong SOS inducer in E.coli [44]), and thus the increased SOS response could promote dissemination of ARGs in environment [45].…”

“…As stated above, not only antibiotics but also considerable numbers of antibioticresistant bacteria, ARGs and associated MGEs are introduced to soil via manure application [8]. Tet genes have been commonly detected in soil adjacent to representative swine feedlots in China [34]. Su et al found that ARGs with manure application account for approximately 70% of the total ARGs in soil, which indicated that manure amendment may increase the diversity and abundance of ARGs in soil [35].…”

Impact of reclaimed water irrigation on antibiotic resistance in public parks, Beijing, China

“…The range of 0.17e 5.07 mg L À1 and 0.10e9.87 mg L À1 for CFX and OFX, respectively, were reported in the effluents of WWTPs in Hong Kong (Leung et al, 2012). In contrast to the wastewater directly irrigated soil (Shi et al, 2012) or the farmlands applied with swine manures (Wu et al, 2010), the concentrations of antibiotics in public park soil were much lower. However, a previous study demonstrated that low concentrations of antibiotics could also induce ARGs and/ or stimulates horizontal gene transfer of ARGs (Storteboom et al, 2010).…”

Long-term field application of sewage sludge increases the abundance of antibiotic resistance genes in soil

“…Manure disposal may transfer ARGs into the environment through a variety of pathways connected with common practice -land application (Joy et al, 2013;Wu et al, 2010). As a common practice, manure application introduces not only nutrients and organic matter for crop growth, but also antimicrobial agents into arable soil (Xiong et al, 2015;Cheng et al, 2013).…”