As antibiotics are restricted or even banned in animal production, more disinfectants are being used to maintain adequate sanitation to prevent bacterial diseases. The use of disinfectant is more than that of antibiotics, especially during the flu pandemic. Widely used quaternary ammonium disinfectants have exacerbated the problem of antimicrobial resistance due to co- and cross-resistances, but the changes of disinfectant-induced antibiotic resistance in the soil environment are unclear.
In a study published in Agriculture, Ecosystems and EnvironmentA research group led by Prof. Yao Huaiying and Prof. Su Jianqiang of the Institute of Urban Environment of the Chinese Academy of Sciences has made progress in understanding the gradient concentrations of exposure to quaternary ammonium disinfectants caused by the co-selection of antibiotic resistance in the bottom.
“The right concentration of disinfectant is one of the most important factors in the selection of resistant bacteria. Especially concentrations at environmental level require special attention,” says Prof. Yao.
A short-term soil microcosm was established to investigate the profile dynamics of the antibiotic resistance gene (ARG) in agricultural soils modified with sulfamethazine (SMZ, 10 mg kg-1) and gradient concentrations of benzalkonium chloride (0, 1, 10, 100 mg kg-1BC(C12), a commonly used class of quaternary ammonium disinfectants).
A unique concentration effect was found on changes in ARG profiles in agricultural soils exposed to different concentrations of BC. With the increase in BC concentration, the number of ARGs detected in the soil increased, while the total ARG abundance decreased.
The highest number of ARGs was observed when exposed to high BC concentrations. Won’t a high concentration of disinfectant directly damage bacteria? Researchers speculated that this phenomenon is related to the adsorption and storage of BC in the soil.
Quaternary ammonium disinfectants are cationic surfactants and their high adsorption affinity for soil particles will decrease their bioavailability, reducing mineralization and their acute toxicity. However, the adsorption and isolation of soil increases the persistence of BC, and the gradual release of BC causes the emergence of more antibiotic resistance.
“Co-selection for antimicrobial resistance only occurs when the concentrations of bioavailable disinfectants are lower than the critical biocide concentration,” says Prof. Yao. “The complexity of the soil environment and the concentration effect of the fumigant have contributed to the development of soil ARG profiles.”
SMZ was added by the researchers to investigate whether SMZ and BC would synergistically promote soil ARG co-selection against the background of combined pollution. Unexpectedly, SMZ and BC had no apparent interaction in shaping the ARG profile in soils. Compared to that of broad-spectrum fungicide BC, the specificity of SMZ had a significant impact on the microbial community. SMZ mainly affected vertical gene transfer of ARGs by altering bacterial host abundance.
This work contributes to future assessments of the public health risks associated with quaternary ammonium disinfectant-induced antibiotic resistance. Disinfectants end up in surface water or soil via sewage pipes and fertilizers. Dilution and degradation result in environmental levels much lower than those used at the time of application. “Future research has yet to focus on the lower BC concentration range,” says Prof. Su.
Single-cell tools provide insight into active antibiotic resistance in soils
Haiyang Yu et al, A meta-analysis of ecological functions and economic benefits of co-culture models in rice fields, Agriculture, Ecosystems and Environment (2022). DOI: 10.116/j.agee.2022.108195
Quote: Exposure to Quaternary Ammonium Disinfectant Promotes Bacterial Antibiotic Resistance in Soils (2022, Oct 17) retrieved Oct 17, 2022 at https://phys.org/news/2022-10-quaternary-ammonium-disinfectant-exposure-bacterial.html
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