Enrichment of the Antibiotic Resistance Gene tet(L) in an Alkaline Soil Fertilized With Plant Derived Organic Manure.

Shuang Peng,Xiangui Lin,Youzhi Feng,Jan Dolfing,Yiming Wang

doi:10.3389/fmicb.2018.01140

Abstract

Fifteen antibiotic resistance genes (ARGs) and intI1, a gene involved in horizontal gene transfer (HGT) of ARGs, were quantified in three different soil samples from a 22 year old field experiment that had received inorganic fertilizer (NPK), organic manure (OM; a mixture of wheat straw, soybean oil cake and cotton cake), and control fields that had received no fertilizer and manure (CK). Tet(L) was the most abundant ARG in OM, which also contained considerable levels of intI1. Molecular analysis of yearly collected archived soils over the past 22 years showed that tet(L) and intI1 were higher in OM soils than in NPK soils. The relative abundance of tet(L) was essentially constant during these years, while the level of intI1 in OM soils decreased over time. The main genotype of tet(L) was the same in archived and in fresh soil, OM, and irrigation water. Phylogenetic analysis of the 16S rRNA genes of tetracycline-resistant bacteria (TRB) isolates indicated that the Firmucutes carrying tet(L) in OM were similar to those in the OM soil, suggesting that OM transferred TRB into the OM soils where they survived. Almost all of the TRB isolated from OM carried tet(L) and belonged to the Firmicutes. Survival of bacteria from the organic manure that carried tet(L) may be the cause of the increased level of tet(L) in OM soil.

Highlights

Antibiotic resistance genes (ARGs) in the environment are posing a global threat to public health (Pruden et al, 2013)
Horizontal gene transfer (HGT) of mobile genetic elements harboring ARGs substantially increases the epidemiological risks associated with antibiotic resistance, because these elements can be readily transferred between bacteria on both an inter- and intra-species level or bi-directionally from non-pathogenic to pathogenic bacteria (Forsberg et al, 2012; Cytryn, 2013)
The distribution of 15 ARGs and two intI genes, normalized to 16S rRNA gene copies, in organic manure (OM) and irrigation water was evaluated by real-time PCR

Summary

Introduction

Antibiotic resistance genes (ARGs) in the environment are posing a global threat to public health (Pruden et al, 2013). Horizontal gene transfer (HGT) of mobile genetic elements harboring ARGs substantially increases the epidemiological risks associated with antibiotic resistance, because these elements can be readily transferred between bacteria on both an inter- and intra-species level or bi-directionally from non-pathogenic to pathogenic bacteria (Forsberg et al, 2012; Cytryn, 2013). The occurrence, abundance, and transferability of ARGs in soil especially increased tet(L) Enriched After OM Fertilized after field application of manure from antibiotic-treated animals (Jechalke et al, 2013; Kyselková et al, 2013; Zhu et al, 2013; Peng et al, 2015, 2017). It has been reported that manure from cattle that had not been treated with antibiotics can lead to increased populations of resident soil bacteria harboring β-lactam resistance genes (Udikovic-Kolic et al, 2014)

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Discussion

Conclusion