鸡粪模拟堆肥中多重耐药菌、耐药基因和整合酶基因的消减动力学解析

为掌握多重耐药菌、耐药基因和整合酶基因在鸡粪堆肥过程中的消减动力学规律，试验外源添加多重耐药菌，并以其携带的磺胺类耐药基因(sul2)、多肽类耐药基因(mcr-1)、喹诺酮类基因(oqxB)和Ⅰ类整合酶基因(intI1)作为典型污染物，开展模拟堆肥试验. 结果表明:可培养的多重耐药大肠杆菌数量在3 d的高温后得到完全灭活；堆肥10 d后，多重耐药菌总量下降了4～6个数量级. 在高温堆肥过程中耐药基因的绝对丰度随着堆肥过程的进行而逐渐降低，耐药基因aadA、sul2、mcr-1、oqxB的消减率分别为89.39%、97.99%、99.89%、99.81%，intI1基因的消减率高于80%；大多数耐药基因的相对丰度表现出先降低后略微升高的趋势. 基于基因绝对丰度的非线性回归分析表明，“独立”耐药基因(oqxB、mcr-1)的消减速率明显高于与Ⅰ类整合酶基因相连的基因(aadA)，多重耐药大肠杆菌16S rRNA基因消减速率为0.128 d?1，半消减期为5.41 d. 堆肥对耐药基因绝对丰度的消减速率高于相对丰度. 研究显示，堆肥可以有效消减鸡粪中多重耐药菌，耐药基因消减规律符合一级动力学方程，与Ⅰ类整合酶基因相连耐药基因消减速率慢于“独立”耐药基因，4种耐药基因的半消减期为1.69~5.81 d. 

Dissipation Kinetics of Multidrug-Resistant Bacteria,Antibiotic Resistance Genes and Integrase Genes during Simulated Composting of Chicken Manure

In order to evaluate the removal kinetics of multidrug-resistant bacteria, antibiotic resistance genes (ARGs) and integrase genes during composting, a laboratory-scale stimulated composting was conducted. Multidrug-resistant bacteria (E. coli 5A5) carrying several typical ARGs, specifically, sulfonamide resistance gene sul2, peptide resistance gene mcr-1, fluoroquinolone resistance gene oqxB, and class Ⅰ integron-integrase gene intI1, were added as exogenous ARGs during composting. The results showed that the cultivable multi-drug resistant E. coli was completely inactivated after 3 days of compositing at high temperature. After 10 days of composting, the total number of multi-drug resistant bacteria decreased by 4-6 lg (CFU/g). During composting, the absolute abundance of ARGs gradually decreased. The removal efficiency of aadA, sul2, mcr-1 and oqxB were 89.39%, 97.99%, 99.89% and 99.81%, respectively, and the removal efficiency of intI1 gene was higher than 80%. The relative abundance of most ARGs showed a trend of decreasing first and then increasing slightly. The non-linear regression analysis of the absolute abundance of ARGs showed that the dissipation rate of ARGs not related to integrase (oqxB, mcr-1) was significantly higher than that of ARGs related to integrase (aadA). The 16S rRNA gene dissipation rate of multidrug resistant E. coli was 0.128 d?1, and the elimination half-life was 5.41 d. The removal rate of the absolute abundance of ARGs was higher than that of the relative abundance of ARGs. The results indicate that composting can effectively reduce the multidrug-resistant bacteria in chicken manure. The dissipation of ARGs follows the first-order kinetic equation. The removal rate of integron-carried ARGs is slower than that of ARGs without integrons. The elimination half-life of the four ARGs were 1.69-5.81 d during composting.