粪肥施用土壤抗生素抗性基因来源、转移及影响因素

随着新型抗生素开发速度的不断下降以及抗性基因(Antibiotic resistant genes,ARGs)的快速出现和传播,细菌抗药性和ARGs对公共健康存在威胁,被公认为当前全球亟待解决的难题。虽然土壤本底存在ARGs,但畜禽粪便施用等人类活动加速了ARGs在土壤环境中的扩散和传播。粪肥施入土壤后,其对土壤微生物的抗性选择压力及基因水平转移导致的ARGs扩散转移将持续存在。畜禽粪便中的抗性细菌所携带的ARGs、土壤中抗生素累积导致微生物产生的ARGs和粪肥刺激含有ARGs微生物的繁殖等均为土壤中ARGs的主要来源。土壤中ARGs可以向水体和农作物传移,并随着食物链向动物及人类传播。自然因素(温度、降水、时间和土壤类型)和人为因素(抗生素的含量和种类、粪便种类和处理方式、重金属含量及生物质炭添加)均会影响土壤中ARGs的持久和扩散。目前,粪肥施用土壤中ARGs污染对环境质量及健康的潜在影响并不完全清楚,建议加强模型建立、溯源、生物地理分布、从污染源向环境介质的转移规律、削减措施和机制等方面研究,以有效遏制ARGs在环境中的污染,真正做到畜禽粪便资源化、无害化利用。

Effects of Manure Application on Source and Transport of Antibiotic Resistant Genes in Soil and Their Affecting Factors

With new antibiotics slowing down in development and antibiotic resistant genes(ARGs)popping up and spreading rapidly,antibiotic resistant bacteria(ARB)and ARGs have become imminent threats to public health and a global problem urgently calling for solution.Nowadays,the industry of livestock breeding still abuses the use of veterinary antibiotics in concentrated feeding operation in an attempt to improve growth and control diseases.It is estimated that approximately 30%~50%of the administered antibiotics are excreted with waste instead of being absorbed by animals.Manure is commonly used as a substitute for inorganic N and P fertilizers for agricultural crops,especially in organic farming.In 2013,a total of 54000 tons of 36 antibiotics was excreted in China,54%into the soil and 46%into the water environment.The antibiotics involved include sulfonamides,tetracycline,fluoroquinolones,macrolides,β-lactam,etc.The ARGs contained in the ARB excreted with manure,generated in microbes as a result of accumulation of antibiotics in soil,and multiplied with the proliferation of ARGs-containing microbes stimulated by manure are the main sources of ARGs in the soil.Bacterial communities in manure and in soil vary sharply in structure.The bacteria in feces can survive in soil for weeks to months,depending on soil and environment,however,horizontal gene transfer from these bacteria to indigenous soil bacteria might rely on persistence of ARGs in soil.As one of the largest and most diverse microbial habitats on earth,soil has been the source of most discovered ARGs,supplying ARGs to water environment,crops,and animals and human through food chain.Once ARB and their corresponding suite of ARGs enter the soil,water and crops,their persistence and fate depend on nature and viability status of their host bacteria and their living environment.Both natural factors,like temperature,rainfall,time and soil type,and human factors,like content and specie of antibiotic,type and treatment of manure,content of heavy metal and biochar addition,could affect persistence and diffusion of ARGs in soil.However,the impacts of manure application contaminating the soil with ARGs on environmental quality and human health still remain unclear.It is,therefore,suggested that studies should be intensified on modelling,source tracing,biogeographical distribution,rules of ARGs transferring from sources to environmental media,measures to reduce and mechanisms of reducing the transfer,which will help to recycle animal waste safely and control pollution of ARGs in the environment effectively.