Abstract
Animal manure is a reservoir of antibiotic resistance genes (ARGs), and direct application of the manure will lead to spread of ARGs in farmland. Here, we explored the impacts of chicken manure and heat-treated chicken manure on the patterns of soil resistome after 3 years’ application, with mushroom residues set as the plant-derived organic manure treatment. A total of 262 ARG subtypes were detected in chicken manure using high-throughput qPCR, and heat treatment can effectively remove 50 types of ARGs. Although ARG subtypes and abundance were both higher in chicken manure, there was no significant difference in the ARG profiles and total ARG abundance among three manure-treated soils. Soil bacteria community compositions were significantly different among manure-treated soils, but they were not significantly correlated with soil ARG profiles. Fast expectation–maximization microbial source tracking (FEAST) was used for quantifying the contributions of the potential sources to microbial taxa and ARGs in manure-fertilized soil. Results revealed that only 0.2% of the chicken manure-derived bacterial communities survived in soil, and intrinsic ARGs were the largest contributor of soil ARGs (95.8–99.7%); ARGs from chicken manure only contributed 0.4%. The total ARG abundance in the heat-treated chicken manure-amended soils was similar to that in the mushroom residue-treated soils, while it was 1.41 times higher in chicken manure-treated soils. Thus, heat treatment of chicken manure may efficiently reduce ARGs introduced into soil and decrease the risk of dissemination of ARGs.
Highlights
The increasing emergence and spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are of great concern worldwide, threatening the efficacy of modern medicines and posing risks to human health (Levy and Marshall, 2004; Su et al, 2015)
The main ARGs in Chicken manure (CM) belong to aminoglycoside, tetracycline, disinfectant, and sulfonamide, while mushroom residues (MR) was dominated by ARGs that belong to beta-lactam, multidrug/other, and phenicols (Figure 1B)
A different pattern was found for Mobile genetic elements (MGEs), with an average number of 25 MGEs detected in CM and K, while MR harbored averagely 27 MGEs
Summary
The increasing emergence and spread of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are of great concern worldwide, threatening the efficacy of modern medicines and posing risks to human health (Levy and Marshall, 2004; Su et al, 2015). Livestock manure is the main source of ARB and ARGs in the agriculture soil environment (Peng et al, 2017; Qian et al, 2017). Compost could still lead to the increased amount of ARGs in soil (Zhu et al, 2013; Peng et al, 2015; Sun et al, 2019). ARB and ARGs in composted manure can spread and promote further development of antibiotic resistance (Kang et al, 2016; Wang et al, 2020a). There is a vital need to further improve the effect of compost practice on ARGs carried by animal feces, monitor ARGs in manure-treated soils, and further examine manure application practices and impacts
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