摘要

耕地上施用粪肥时，兽医用抗生素、细菌携带的位于流动遗传元件和营养物质上的抗生素抗性决定因子，通过粪肥在农业土壤上传播。然而，评估环境风险需要的粪便中抗生素浓度和抗生素抗性基因( ARGs )与环境相关的系统定量研究很少。在这个微型研究中，将砂土和壤土与以五种浓度添加了链霉素或多西环素的肥料混合。在第28天和92天提取全部菌落DNA，用qPCR方法测定16S rRNA基因中ARGs ( aadA、strA、Tet ( A )、Tet ( M )、Tet ( W )、Tet ( Q )、su1、qacE / qacesδ1 )和整合子整合酶1、2类基因( intl 1、intl 2 )的丰度。通过16S rRNA基因扩增子的变性梯度凝胶电泳评价其对细菌群落组成的影响。施用有机肥显著增加了大多数供试基因的相对丰度。抗生素引起了进一步的富集，随着时间的推移而减少，并且主要以高浓度出现。值得注意的是，沙地土壤对相关基因丰度和土壤细菌群落组成的影响更为显著。由于各种影响因素，为环境风险评估定义抗生素阈值浓度的概念仍然具有挑战性。

Veterinary antibiotics, bacteria carrying antibiotic resistance determinants located on mobile genetic elements and nutrients are spread on agricultural soil using manure as fertilizer. However, systematic quantitative studies linking antibiotic concentrations and antimicrobial resistance genes (ARGs) in manure and the environment are scarce but needed to assess environmental risks. In this microcosm study, a sandy and a loamy soil were mixed with manure spiked with streptomycin or doxycycline at five concentrations. Total-community DNA was extracted on days 28 and 92, and the abundances of ARGs (aadA, strA, tet(A), tet(M), tet(W), tet(Q), sul1, qacE/qacEΔ1) and class 1 and 2 integron integrase genes (intI1 and intI2) were determined by qPCR relative to 16S rRNA genes. Effects on the bacterial community composition were evaluated by denaturing gradient gel electrophoresis of 16S rRNA gene amplicons. Manure application to the soils strongly increased the relative abundance of most tested genes. Antibiotics caused further enrichments which decreased over time and were mostly seen at high concentrations. Strikingly, the effects on relative gene abundances and soil bacterial community composition were more pronounced in sandy soil. The concept of defining antibiotic threshold concentrations for environmental risk assessments remains challenging due to the various influencing factors.

https://academic.oup.com/femsec/article-abstract/94/2/fix145/4566514?redirectedFrom=fulltext