Singh Harshita, Bagra Kenyum, Dixit Sourabh, Singh Awanish Kumar, Singh Gargi
Department of Civil Engineering, Indian Institute of Technology, Roorkee 247667, India.
College of Veterinary and Animal Science, G.B. Pant University of Agriculture and Technology, Pantnagar, Udham Singh Nagar 263145, India.
Prev Vet Med. 2025 Jun;239:106497. doi: 10.1016/j.prevetmed.2025.106497. Epub 2025 Mar 4.
The dairy industry in developing countries is often associated with inappropriate use of antibiotics and the subsequent contamination of the environment with co-selectors of antibiotic resistance. However, the specific factors in dairy farm environments that influence antibiotic resistance levels and the subsequent exposure risks to farm workers are unknown. We examined the link between the infrastructure and operations of the dairy farm and the antibiotic resistance potential in India, which is the highest producer and consumer of dairy products globally. We sampled sixteen dairy farms in the Dehradun district, India, that varied in their herd size, infrastructure, and operational features during winter, summer, and monsoon. We collected samples of dung, manure, wastewater, manure-amended, and control soil from these farms. We quantified six antibiotic resistance genes (ARGs) (sul1, sul2, parC, mcr5, ermF, and tetW), an integron integrase gene cassette (intI1), and 16S rRNA gene copies as an indicator for total bacterial count. We observed that the infrastructure and the operations of the dairy farms were significantly associated with antibiotic resistance potential in the dairy environment. For example, with increased ventilation and exposure to external weather, the levels of sul2 (x͂=10) and parC (x͂=10) in manure increased. When farmers administered antibiotics without veterinary consultation, the relative levels of intI1 (x͂=10), sul2 (x͂=10), and tetW (x͂=10) in manure were lower than the cases where professional advice was sought. Small-scale farms had lower relative ARG levels than medium- and large-scale farms, except for mcr5 (x͂=10) in wastewater. In different sample types, the relative ARG levels trended as manure-amended soil (x͂=10) > wastewater (x͂=10)> manure (x͂=10)> dung (x͂=10). ARGs correlated with the marker for horizontal gene transfer, intI1, which exacerbates overall antibiotic resistance levels. Exposure assessment showed that the agriculture farm workers working in manure-amended agriculture farms are exposed to higher antibiotic resistance potential than dairy farm workers, who manually handle dung. Our study showed that the link between the dairy infrastructure (ventilation and floor type) and operations (scale of operation and veterinary consultation) and the antibiotic resistance potential in the dairy farm environment was statistically significant. This knowledge paves the way for designing interventions that can minimize the antibiotic resistance potential on dairy farms and in affected environments and thus reduce the public health burden of antibiotic-resistant infections in the dairy industry and dairy workers in India.
发展中国家的乳制品行业常与抗生素的不当使用以及随后环境被抗生素耐药性共选因子污染有关。然而，奶牛场环境中影响抗生素耐药水平以及农场工人后续接触风险的具体因素尚不清楚。我们研究了印度奶牛场的基础设施和运营与抗生素耐药潜力之间的联系，印度是全球最大的乳制品生产国和消费国。我们在印度德拉敦地区对16个奶牛场进行了采样，这些奶牛场在冬季、夏季和季风季节的畜群规模、基础设施和运营特征各不相同。我们从这些农场采集了粪便、粪肥、废水、施粪肥土壤和对照土壤样本。我们对6种抗生素抗性基因（ARGs）（sul1、sul2、parC、mcr5、ermF和tetW）、一个整合子整合酶基因盒（intI1）以及16S rRNA基因拷贝数进行了定量，作为总细菌数的指标。我们观察到，奶牛场的基础设施和运营与奶牛场环境中的抗生素耐药潜力显著相关。例如，随着通风增加和外部天气暴露，粪肥中sul2（x̅=10）和parC（x̅=10）的水平升高。当农民在没有兽医咨询的情况下使用抗生素时，粪肥中intI1（x̅=10）、sul2（x̅=10）和tetW（x̅=10）的相对水平低于寻求专业建议的情况。除了废水中的mcr5（x̅=10）外，小规模农场的相对ARG水平低于中型和大型农场。在不同的样本类型中，相对ARG水平的趋势为：施粪肥土壤（x̅=10）>废水（x̅=10）>粪肥（x̅=10）>粪便（x̅=10）。ARGs与水平基因转移标记intI1相关，这加剧了整体抗生素耐药水平。暴露评估表明，在施粪肥农场工作的农业农场工人比手动处理粪便的奶牛场工人面临更高的抗生素耐药潜力。我们的研究表明，奶牛场基础设施（通风和地面类型）和运营（运营规模和兽医咨询）与奶牛场环境中的抗生素耐药潜力之间的联系具有统计学意义。这一知识为设计干预措施铺平了道路，这些干预措施可以将奶牛场及受影响环境中的抗生素耐药潜力降至最低，从而减轻印度乳制品行业和乳制品工人中抗生素耐药感染的公共卫生负担。
