Metagenomic analysis of antibiotic resistance genes (ARGs) during refuse decomposition

Landfill is important reservoirs of residual antibiotics and antibiotic resistance genes (ARGs), but themechanism of landfill application influence on antibiotic resistance remains unclear. Although refuse decomposition plays a crucial role in landfill stabilization, its impact on the antibiotic resistance has not been well characterized. To better understand the impact, we studied the dynamics of ARGs and the bacterial community composition during refuse decomposition in a bench-scale bioreactor after long term operation (265 d) based onmetagenomics analysis. The total abundances of ARGs increased from431.0 ppmin the initial aerobic phase (AP) to 643.9 ppmin the latermethanogenic phase (MP) during refuse decomposition, suggesting that application of landfill formunicipal solid waste (MSW) treatment may elevate the level of ARGs. A shift from drug-specific (bacitracin, tetracycline and sulfonamide) resistance to multidrug resistance was observed during the refuse decomposition and was driven by a shift of potential bacteria hosts. The elevated abundance of Pseudomonas mainly contributed to the increasing abundance of multidrug ARGs (mexF and mexW). Accordingly, the percentage of ARGs encoding an efflux pump increased during refuse decomposition, suggesting that potential bacteria hosts developed this mechanism to adapt to the carbon and energy shortage when biodegradable substances were depleted. Overall, our findings indicate that the use of landfill forMSW treatment increased antibiotic resistance, and demonstrate the need for a comprehensive investigation of antibiotic resistance in landfill. (C) 2018 Elsevier B.V. All rights reserved.