Antibiotic Resistance Genes and Associated Microbial Community Conditions in Aging Landfill Systems

Abstract

Landfills receive about 350 million tons of municipal solid wastes (MSWs) per year globally, including antibiotics and other coselecting agents that impact antimicrobial resistance (AMR). However, little is known about AMR in landfills, especially as a function of landfill ages. Here we quantified antibiotics, heavy metals, and AMR genes (ARGs) in refuse and leachates from landfills of different age (<3, 10, and >20 years). Antibiotics levels were consistently lower in refuse and leachates from older landfills, whereas ARG levels in leachates significantly increased with landfill age (One-way ANOVA, F = 10.8, P < 0.01). Heavy metals whose contents increased as landfills age (one-way ANOVA, F = 12.3, P < 0.01) were significantly correlated with elevated levels of ARGs (Mantel test, R = 0.66, P < 0.01) in leachates, which implies greater AMR exposure risks around older landfills. To further explain ARGs distributional mechanisms with age, microbial communities, mobile genetic elements (MGEs) and environmental factors were contrasted between refuse and leachate samples. Microbial communities in the refuse were closely correlated with ARG contents (Procrustes test; M = 0.37, R = 0.86, P < 0.001), whereas ARG in leachates were more associated with MGEs.

Satellite tracking of gulls and genomic characterization of faecal bacteria reveals environmentally mediated acquisition and dispersal of antimicrobial‐resistant Escherichia coli on the Kenai Peninsula, Alaska

“…We infer that many of the gulls inhabiting this breeding colony utilize the Soldotna landfill for forage, providing a source by which gulls may acquire AMR E. coli and/or AMR genes (Ahlstrom et al, ; Atterby et al, ). This is supported by (a) our findings that the majority of observed gull transitions occurred between the lower Kenai River and Soldotna landfill throughout the study period, and the diurnal pattern of gull attendance at the Soldotna landfill appeared to be correlated with landfill operating hours; (b) our regular observations of gulls feeding at the landfill over the course of this study; and (c) the fact that digested sludge from regional wastewater treatment facilities, in addition to commercial and household waste material, is disposed of at the Soldotna landfill, all of which may be reservoirs of AMR (Rizzo et al, ; Wu, Huang, Sun, Graham, & Xie, ). Thus, it is probable that gulls acquire and maintain AMR E. coli for at least short periods of time and disperse them to other areas they regularly occupy such as the lower Kenai River breeding colony.…”

Horizontal gene transfer and shifts in linked bacterial community composition are associated with maintenance of antibiotic resistance genes during food waste composting

“…Composting properties also had direct positive effects on bacterial community composition and alpha-diversity, and indirect positive effects on MGE abundances via bacterial community composition. MGEs have recently been proposed to have a more important role in the spread of ARGs than the microbial community composition or microbial diversity (Ma et al, 2017;Wu et al, 2017). One possible reason may be that MGEs are very successful at mobilizing ARGs in environmental microbial communities via horizontal gene transfer (Wang et al, 2017a).…”

“…If ARGs enter humans via the food chain, the efficiency of antibiotics could be reduced. While the diversity and abundance of ARGs and MGEs has been studied largely in the process of manure and sewage sludge composting (Ma et al, 2015;Su et al, 2017b;Wu et al, 2017), there are no studies investigating ARG and MGE dynamics during FW composting. Even though most food products do not normally contain antibiotics, the emergence of abundant ARGs have been found in some food products such as meat and dairy products (Wang et al, 2012).…”

Metagenomic analysis reveals the shared and distinct features of the soil resistome across tundra, temperate prairie and tropical ecosystems

“…Further studies demonstrate that some anthropogenic activities signi cantly enrich the abundance of indigenous ARGs in soils [9][10][11]. Understanding soil resistomes at a broad geographic scale and across various ecosystems, especially in native soils which haven't been exposed to anthropogenic activities, can help better de ne the background levels and types of ARGs, which is essential for assessing the impact and potential risk of new human activities.…”