Dep. of Civil and Environmental Engineering, Univ. of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
Dep. of Biological Systems Engineering, Univ. of Nebraska-Lincoln, Lincoln, NE, 68583, USA.
J Environ Qual. 2020 May;49(3):745-753. doi: 10.1002/jeq2.20017. Epub 2020 Mar 18.
Manure is commonly used as a fertilizer or soil conditioner; however, land application of untreated manure may introduce pathogens and antibiotic-resistant bacteria (ARB) into the soil, with harmful implications for public health. Composting is a manure management practice wherein a carbon-rich bulking agent, such as corn (Zea mays L.) stalk residue, is added to manure to achieve desirable carbon/nitrogen ratios to facilitate microbial activities and generate enough heat to inactivate pathogens, including antibiotic-resistant pathogens. However, when comparing compost piles and stockpiles for ARB reduction, we noticed that bulking agents added ARB to composting piles and compromised the performance of composting in reducing ARB. We hypothesized that ARB could be prevalent in corn stalk residues, a commonly used bulking agent for composting. To test this hypothesis, corn stalk residue samples throughout Nebraska were surveyed for the presence of ARB. Of the samples tested, 54% were positive for antibiotic-resistant Escherichia coli or enterococci using direct plating or after enrichment. Although not statistically significant, there was a trend wherein the use of pesticides tended to result in a greater prevalence of some ARB. Results from this study suggest that bulking agents can be a source of ARB in manure composting piles and highlight the importance of screening bulking agents for effective ARB reduction in livestock manure during composting.
粪便通常被用作肥料或土壤改良剂；然而，未经处理的粪便施用于土地可能会将病原体和抗生素耐药菌（ARB）引入土壤，对公共健康造成有害影响。堆肥是一种粪便管理实践，其中添加富含碳的膨松剂，如玉米（Zea mays L.）秸秆残体，以达到理想的碳/氮比，促进微生物活动并产生足够的热量来灭活病原体，包括抗生素耐药病原体。然而，在比较堆肥堆和堆肥库存以减少 ARB 时，我们注意到膨松剂会向堆肥堆中添加 ARB，并影响堆肥减少 ARB 的性能。我们假设 ARB 可能在玉米秸秆残体中普遍存在，玉米秸秆残体是堆肥中常用的膨松剂。为了验证这一假设，对内布拉斯加州各地的玉米秸秆残体样本进行了抗生素耐药大肠杆菌或肠球菌的存在情况调查。在测试的样本中，直接平板或富集后，有 54%的样本对抗生素耐药大肠杆菌或肠球菌呈阳性。虽然没有统计学意义，但有一个趋势表明，使用农药往往会导致某些 ARB 的流行程度增加。这项研究的结果表明，膨松剂可能是粪便堆肥堆中 ARB 的来源，并强调了在堆肥过程中筛选膨松剂以有效减少牲畜粪便中 ARB 的重要性。
