Low nitrogen in biogas slurry application mitigates antibiotic resistance genes in soil

Varying characteristics and driving mechanisms of antibiotic resistance genes in farmland soil amended with high-density polyethylene microplastics

Distribution of antibiotic resistance genes in soil amended using Azolla imbricata and its driving mechanisms.

Factors that affect the occurrence and distribution of antibiotic resistance genes in soils from livestock and poultry farms

Large quantities of livestock manure not only occupy farmland but also serve as the primary source of antibiotics and antibiotic resistance genes (ARGs) in agricultural soil. To enhance the resource utilization of animal manure and mitigate ecological risks associated with antibiotics in agroecosystems, chicken manure was used as a raw material for biochar production. The manure derived biochar (MB) was modified with an alkali–acid two‐step modification process. The results showed that the total pore volume and surface area of alkali–acid modified MB (AMMB) was significantly increased about three and five times, respectively after modification. The SEM images showed that the surface of AMMB had a more regular and clearer structure with fewer impurities. The improvement of surface properties of AMMB significantly increased its adsorbing capacity of tetracycline in the soil. The adsorption kinetics of tetracycline by AMMB were better fitted by the pseudo‐second‐order kinetic model, suggesting that the adsorption of tetracycline on biochar followed the process of chemisorption. The adsorption mechanisms mainly involved the pore filling, hydrophobic effect, and π–π EDA interaction. Moreover, after a 60 days amendment of AMMB, the total relative abundances (RAs) of tested tetracycline resistance genes (TRGs) in soil decreased significantly, which suggested that AMMB can be a potential material to reduce risks of antibiotics and its resistance genes.

Fertilizing drug resistance: Dissemination of antibiotic resistance genes in soil and plant bacteria under bovine and swine slurry fertilization

Functional metagenomic characterization of antibiotic resistance genes in agricultural soils from China

Reducing antibiotic resistance genes in soil: The role of organic materials in reductive soil disinfestation.

Uncovering the prevalence and drivers of antibiotic resistance genes in soils across different land-use types

Soil is an important environmental reservoir of antibiotic resistance genes (ARGs), which are increasingly recognized as environmental contaminants. Methods to assess the risks associated with the acquisition or transfer of resistance mechanisms are still underdeveloped. Quantification of background levels of antibiotic resistance genes and what alters those is a first step in understanding our environmental resistome. Toward this goal, 62 samples were collected over 3 years from soils near the 30-year old Gondwana Research Station and for 4 years before and during development of the new Jang Bogo Research Station, both at Terra Nova Bay in Antarctica. These sites reflect limited and more extensive human impact, respectively. A qPCR array with 384 primer sets targeting antibiotic resistance genes and mobile genetic elements (MGEs) was used to detect and quantify these genes. A total of 73 ARGs and MGEs encompassing eight major antibiotic resistance gene categories were detected, but most at very low levels. Antarctic soil appeared to be a common reservoir for seven ARGs since they were present in most samples (42%-88%). If the seven widespread genes were removed, there was a correlation between the relative abundance of MGEs and ARGs, more typical of contaminated sites. There was a relationship between ARG content and distance from both research stations, with a significant effect at the Jang Bogo Station especially when excluding the seven widespread genes; however, the relative abundance of ARGs did not increase over the 4 year period. Silt, clay, total organic carbon, and SiO2 were the top edaphic factors that correlated with ARG abundance. Overall, this study identifies that human activity and certain soil characteristics correlate with antibiotic resistance genes in these oligotrophic Antarctic soils and provides a baseline of ARGs and MGEs for future comparisons.

Effects of reductive soil disinfestation on potential pathogens and antibiotic resistance genes in soil

The increasing antibiotic resistance genes (ARGs) in fertilizer-amended soils can potentially enter food chains through their transfer in a soil–vegetable system, thus, posing threats to human health. As nitrogen is an essential nutrient in agricultural production, the effect of nitrogen (in the forms NH4+-N and NO3−-N) on the distribution of ARGs (blaTEM-1, sul1, cmlA, str, and tetO) and a mobile genetic element (MGE; tnpA-4) in a soil–Chinese cabbage system was investigated. Not all the tested genes could transfer from soil to vegetable. For transferable ones (blaTEM-1, sul1, and tnpA-4), nitrogen application influenced their abundances in soil and vegetable but did not impact their distribution patterns (i.e., preference to either leaf or root tissues). For ARGs in soil, effects of nitrogen on their abundances varied over time, and the positive effect of NH4+-N was more significant than that of NO3−-N. The ARG accumulation to vegetables was affected by nitrogen application, and the nitrogen form was no longer a key influencing factor. In most cases, ARGs were found to prefer being enriched in roots, and nitrogen application may slightly affect their migration from root to leaf. The calculated estimated human intake values indicated that both children and adults could intake 106–107 copies of ARGs per day from Chinese cabbage consumption, and nitrogen application affected ARG intake to varying degrees. These results provided a new understanding of ARG distribution in vegetables under the agronomic measures such as nitrogen application, which may offer knowledge for healthy vegetable cultivation in future.

Pyroligneous acid mitigated dissemination of antibiotic resistance genes in soil

Antibiotic resistance genes (ARGs) in soil pose a major challenge to global environment and health. The development of effective technologies to reduce their negative effects has implications for maintaining soil health and human health. Biochar would be a suitable control material due to its characteristics of high carbon content, large surface area, excellent adsorption capacity, and economic advantages. There are three mechanisms underlying its negative effects on the abundance of ARGs: 1) adsorption of certain pollutants (e.g., antibiotics and heavy metals) to reduce the co-selective pressure of ARGs; 2) alteration of microbial composition through altering soil physico-chemical properties, and thereby limiting the ability of bacteria to undergo horizontal transfer of ARGs; 3) direct impairment of horizontal gene transfer by the adsorption of horizontal transfer vectors such as plasmids, transposons, and integrons. However, the negative effect of biochar depends on the source of material, pyrolysis process, and its amount added. Furthermore, field aging of biochar may reduce its ability to block ARGs. Endogenous contaminants of biochar, such as polycyclic aromatic hydrocarbons and heavy metals, may cause the enrichment of specific antibiotic-resistant bacteria in the environment or induce horizontal gene transfer. In further studies, suitable biochar should be selected according to soil environments, and biochar aging control measures should be taken to improve its retarding effect on ARGs.

Removal of chlortetracycline and antibiotic resistance genes in soil by earthworms (epigeic Eisenia fetida and endogeic Metaphire guillelmi)

Composting increased persistence of manure-borne antibiotic resistance genes in soils with different fertilization history