Department of Dairy Science, Virginia Tech, Blacksburg, VA, USA.
Department of Animal Sciences, School of Agriculture, Policy and Development, University of Reading, Reading RG6 6AR, UK.
Sci Total Environ. 2020 Mar 25;710:136310. doi: 10.1016/j.scitotenv.2019.136310. Epub 2019 Dec 26.
Quantifying the fate of antibiotics and antibiotic resistance genes (ARGs) in response to physicochemical factors during storage of manure slurries will aid in efforts to reduce the spread of resistance when manure is land-applied. The objectives of this study were to determine the effects of temperature (10, 35, and 55 °C) and initial pH (5, 7, 9, and 12) on the removal of pirlimycin and prevalence of ARGs during storage of dairy manure slurries. We collected and homogenized feces and urine from five lactating dairy cows treated with pirlimycin and prepared slurries by mixing manure and sterile water. Aliquots (200 mL) of slurry were transferred and incubated in 400 mL glass beakers under different temperatures (10, 35, and 55 °C) or initial pH (5, 7, 9, and 12). Pirlimycin concentration and abundances of 16S rRNA, mefA, tet(W), and cfxA as indicators of total bacteria and ARGs corresponding to macrolide, tetracycline, and β-lactam resistance, respectively, were analyzed during manure incubation. The thermophilic environment (55 °C) increased the deconjugation and removal of pirlimycin, while the acidic shock at pH 5 increased deconjugation but inhibited removal of pirlimycin, suggesting that the chemical stability of pirlimycin could be affected by temperature and pH. The thermophilic environment decreased mefA relative abundance on day 7 and 28 (P = 0.02 and 0.04), which indicates that the bacteria that encoded mefA gene were not thermotolerant. Although mefA relative abundance was greater at the pH 9 shock than the rest of pH treatments on day 7 (P = 0.04), no significant pH effect was observed on day 28. The tet(W) abundance under initial pH 12 shock was less than other pH shocks on day 28 (P = 0.01), while no temperature effect was observed on day 28. There was no significant temperature and initial pH effect on cfxA abundance at any time point during incubation, implying that the bacteria that carrying cfxA gene are relatively insensitive to these environmental factors. Overall, directly raising temperature and pH can facilitate pirlimycin removal and decrease mefA and tet(W) relative abundances during storage of manure slurries.
量化抗生素和抗生素抗性基因（ARGs）在粪便泥浆储存过程中应对理化因素的命运，将有助于减少粪肥施用时抗性的传播。本研究的目的是确定温度（10、35 和 55°C）和初始 pH（5、7、9 和 12）对奶牛粪便泥浆储存过程中吡利霉素的去除和 ARGs 流行率的影响。我们收集并混合了五头接受吡利霉素治疗的泌乳奶牛的粪便和尿液，并通过混合粪便和无菌水来制备泥浆。将 200 毫升泥浆等分试样转移并在不同温度（10、35 和 55°C）或初始 pH（5、7、9 和 12）下在 400 毫升玻璃烧杯中孵育。在粪便孵育过程中分析了吡利霉素浓度和 16S rRNA、mefA、tet(W)和 cfxA 的丰度，mefA 作为大环内酯、四环素和β-内酰胺抗性的指示物，tet(W)和 cfxA 分别作为总细菌和相应抗生素抗性基因的指标。嗜热环境（55°C）增加了吡利霉素的去结合和去除，而 pH 5 的酸性冲击增加了去结合但抑制了吡利霉素的去除，这表明吡利霉素的化学稳定性可能受到温度和 pH 的影响。嗜热环境降低了第 7 天和第 28 天 mefA 的相对丰度（P=0.02 和 0.04），这表明编码 mefA 基因的细菌不耐热。尽管在第 7 天 pH9 冲击时 mefA 的相对丰度大于其余 pH 处理（P=0.04），但在第 28 天没有观察到显著的 pH 效应。在第 28 天初始 pH12 冲击下 tet(W)的丰度小于其他 pH 冲击（P=0.01），而在第 28 天没有观察到温度效应。在孵育过程中的任何时间点，cfxA 的丰度都没有受到温度和初始 pH 的显著影响，这意味着携带 cfxA 基因的细菌对这些环境因素相对不敏感。总体而言，直接升高温度和 pH 可以促进吡利霉素的去除，并降低粪便泥浆储存过程中 mefA 和 tet(W)的相对丰度。
