Department of Civil, Construction and Environmental Engineering, Marquette University, Milwaukee, WI, USA; Soil and Water Sciences Department, University of Florida, Gainesville, FL, USA.
Department of Civil, Construction and Environmental Engineering, Marquette University, Milwaukee, WI, USA; Brown & Caldwell, Charlotte, NC, USA.
Environ Pollut. 2018 Oct;241:1182-1190. doi: 10.1016/j.envpol.2018.06.048. Epub 2018 Jun 19.
Triclosan (TCS) is a broad-spectrum antimicrobial used in a variety of consumer products. While it was recently banned from hand soaps in the US, it is still a key ingredient in a top-selling toothpaste. TCS is a hydrophobic micropollutant that is recalcitrant under anaerobic digestion thereby resulting in high TCS concentrations in biosolids. The objective of this study was to determine the impact of TCS on the antibiotic resistome and potential cross-protection in lab-scale anaerobic digesters using shotgun metagenomics. It was hypothesized that metagenomics would reveal selection for antibiotic resistance genes (ARGs) not previously found in pure culture studies or mixed-culture studies using targeted qPCR. In this study, four different levels of TCS were continuously fed to triplicate lab-scale anaerobic digesters to assess the effect of TCS levels on the antibiotic resistance gene profiles (resistome). Blasting metagenomic reads against antibiotic/metal resistance gene database (BacMet) revealed that ARG diversity and abundance changed along the TCS concentration gradient. While loss of bacterial diversity and digester function were observed in the digester treated with the highest TCS concentration, FabV, which is a known TCS resistance gene, increased in this extremely high TCS environment. The abundance of several other known ARG or metal resistance genes (MRGs), including corA and arsB, also increased as the concentrations of TCS increased. Analysis of other functional genes using SEED database revealed the increase of potentially key genes for resistance including different types of transporters and transposons. These results indicate that antimicrobials can alter the abundance of multiple resistance genes in anaerobic digesters even when function (i.e. methane production) is maintained. This study also suggests that enriched ARGs could be released into environments with biosolids land application.
三氯生（TCS）是一种广谱抗菌剂，用于多种消费产品。尽管它最近已被禁止用于美国的洗手液，但它仍是一种畅销牙膏的关键成分。TCS 是一种疏水性微污染物，在厌氧消化条件下难以降解，因此导致生物固体中的 TCS 浓度很高。本研究的目的是使用高通量宏基因组学确定 TCS 对实验室规模厌氧消化器中抗生素抗性组的影响和潜在的交叉保护作用。假设宏基因组学将揭示以前在纯培养研究或使用靶向 qPCR 的混合培养研究中未发现的抗生素抗性基因（ARGs）的选择。在这项研究中，连续向 4 个不同水平的 TCS 喂养三重复实验室规模的厌氧消化器，以评估 TCS 水平对抗生素抗性基因谱（抗性组）的影响。将宏基因组读取与抗生素/金属抗性基因数据库（BacMet）进行 Blast 揭示了随着 TCS 浓度梯度的变化，ARG 多样性和丰度发生了变化。虽然在 TCS 浓度最高的处理消化器中观察到细菌多样性和消化器功能丧失，但 FabV 增加，FabV 是已知的 TCS 抗性基因。在这种极高的 TCS 环境中，几种其他已知的 ARG 或金属抗性基因（MRGs）的丰度也增加了，包括 corA 和 arsB。使用 SEED 数据库对其他功能基因进行分析表明，包括不同类型的转运蛋白和转座子在内的潜在关键抗性基因的数量增加。这些结果表明，即使功能（即甲烷产生）得以维持，抗生素也可以改变厌氧消化器中多种抗性基因的丰度。本研究还表明，富含 ARG 的物质可能会随着生物固体土地应用而释放到环境中。
