摘要

    通过对不同温度和pH处理下的有机肥中抗生素和抗生素耐药基因（ARG）的定量分析有助于指导开发具有成本效益的有机肥处理方法，最大限度地减少有机肥施用后抗生素抗性的传播。本研究旨在探讨不同温度和初始pH值对牛粪浆中头孢菌素类抗生素和抗生素耐药基因（ARG）存在性的影响。以5头健康奶牛为研究对象，在干燥条件下用头孢匹林（cephapirin，头孢菌素类抗生素）进行肌肉注射，收集粪便和尿液，与无菌水混合制成粪浆。在28天的孵育研究中，牛粪浆或者连续暴露在3种温度（10、35和55°C）中的1种，或者接受各种初始pH值（5、7、9和12）的刺激。在所有处理后的初始样品中和第一天都检测到了头孢匹灵，但此后检测不到。这表明，无论温度和pH值如何，头孢匹林都能迅速降解。然而，与低温环境（10°C）相比，在中温（35°C）和高温（55°C）环境下，头孢匹林第一天的降解更大。在初始碱性调整（pH 9和12）后的第一天，头孢匹林的浓度低于中性和酸性调整（pH 7和5）后的浓度，因此pH值超过中性也会加速头孢匹林降解。温度和初始pH值对β-内酰胺类ARG、cfxA和四环素类ARG、tet（W）的丰度没有显著影响，说明编码cfxA或tet（W）基因的细菌对牛粪中的温度和pH值不敏感。然而，大环内酯类ARG、mefA的丰度在嗜冷和嗜热环境中以及暴露于强碱性刺激（pH 12）后均降低。我们的研究结果表明，在牛粪浆储存过程中提高温度或pH值，可以与其他适合于减少有机肥施用后ARG从肥料转移到环境中的农场做法一起使用。

     Quantifying antibiotics and antibiotic resistance genes (ARG) in manure exposed to various temperature and pH treatments could guide the development of cost-effective manure handling methods to minimize the spread of antibiotic resistance following land application of manure. This study aimed to investigate the effect of various temperatures and initial pH shocks on the persistence of a cephalosporin antibiotic and ARG in dairy manure slurries. Feces and urine were collected from 5 healthy dairy cows administered with cephapirin (cephalosporin antibiotic) at dry-off via intramammary infusion and were mixed with sterile water to generate manure slurries. In a 28-d incubation study, dairy manure slurries either were continuously exposed to 1 of 3 temperatures (10, 35, and 55°C) or received various initial pH (5, 7, 9, and 12) shocks. Cephapirin was detected in the initial samples and on d 1 following all treatments, but it was undetectable thereafter. This indicates that cephapirin can be rapidly degraded irrespective of temperature and pH treatments. However, degradation was greater on d 1 with the mesophilic (35°C) and thermophilic (55°C) environments compared with the psychrophilic environment (10°C). Increasing pH beyond neutral also accelerated degradation as cephapirin concentrations were lower on d 1 after initial alkaline adjustments (pH 9 and 12) than after neutral and acidic adjustments (pH 7 and 5). No significant effect of temperature or initial pH was observed on abundances of a β-lactam ARG, cfxA, and a tetracycline ARG, tet(W), implying that bacteria that encoded cfxA or tet(W) genes were not sensitive to temperature or pH in dairy manure slurries. However, abundances of a macrolide ARG, mefA, were decreased in the psychrophilic and thermophilic environments and also following exposure to a strong alkaline shock (pH 12). Our results suggest that increasing temperature or pH during storage of dairy manure slurries could be used together with other on-farm practices that are tailored to reduce the transfer of ARG from manure to the environment following land application.

     https://www.sciencedirect.com/science/article/pii/S0022030220300357