鸡粪肥还田过程中的大肠杆菌耐药性与传播风险

Antibiotic Resistance and Transmission Risk of Escherichia coli during the Application of Chicken Manure Fertilizers to Cropland

粪肥还田是一种被广泛采用的养殖粪污资源化利用方式。为探讨不同形式的鸡粪肥对农田土壤中菌株耐药性的影响,以及可能的耐药性传播风险,选取露天大田模拟粪肥还田过程,分离新鲜鸡粪和有机肥样品以及施用两种粪肥的土壤样品中的大肠杆菌,利用微量肉汤稀释法检测分离株的耐药性,利用PCR法鉴定分离菌的MLST分型。结果显示:从采集的220份不同样品中共分离鉴定到57株大肠杆菌,鲜鸡粪组大肠杆菌总分离率为49.5%,有机肥组为4.8%。在21株菌株药敏试验中,分离菌株对9类14种抗菌药均有不同程度的耐药性,多重耐药率高达95.2%,大肠杆菌耐药率在土壤中随时间推移总体呈下降趋势。在大肠杆菌中鉴定到33种ST分型,其中ST10为相对优势基因型(9/56),ST10、ST8774、ST8900和ST533为多种样品共有ST型。结果表明,鲜鸡粪组大肠杆菌污染风险高于有机肥组,粪肥中的大肠杆菌及其耐药基因可传播至土壤中,但耐药率会随时间推移而降低。建议对粪肥处理后还田,以降低大肠杆菌污染及耐药性传播风险。

Application of manure fertilizers to cropland is commonly used to recover manure from farms.In order to investigate the influence of chicken manure fertilizers in different forms on antibiotic resistance of bacterial strains in farmland soil as well as possible risk of resistance transmission,open land for growing field crops was selected to simulate the process of application of manure to cropland,and Escherichia coli(E.coli)was isolated from farmland soil applied with fresh chicken manure and organic fertilizer samples as well as with the two types of manure,and the isolates were tested for drug resistance using broth microdilution methods and identified by PCR for ML ST typing.The results showed that 57 strains were isolated and identified from 220 samples,with a total isolation rate of 49.5% in the fresh manure group and 4.8% in the organic manure group.In the drug sensitivity test for 21 strains,the isolates were resistant to 14 antimicrobial drugs under 9 categories to different extent,with a multi-drug resistance rate of 95.2%,and the drug resistance rate of E.coli tended to decrease generally in soil over time.33 ST subtypes were identified,including ST10 as a relatively dominant genotype(9/56),and ST10,ST8774,ST8900 and ST533 subtypes were common.In conclusion,the risk of E.coli contamination was higher in the fresh manure group than that in the organic manure group,E.coli and its resistance genes contained in manure could be transmitted to soil,but their resistance rate decreased over time.It was recommended to process manure prior to its application to cropland to reduce possible risk of E.coli contamination and resistance transmission.