Qi Yijian, Lu Zhiyuan, Meng Ziru, Wang Xiaozhou, Chen Huahua, Li Muzi, Qu Chaonan, Zhang Pu, Liu Yongxia, Liu Jianzhu
College of Veterinary Medicine, Shandong Agricultural University, Tai'an, Shandong, China.
Shandong Provincial Key Laboratory of Zoonoses, Shandong Agricultural University, Tai'an, China.
Front Vet Sci. 2025 Jul 23;12:1649876. doi: 10.3389/fvets.2025.1649876. eCollection 2025.
This study systematically analyzed bacterial diversity and antimicrobial resistance (AMR) profiles in bulk tank milk from five dairy farms ( = 30) in Shandong Province, China, to assess public health risks associated with microbial contamination and provide critical data for regional quality control and AMR risk assessment in dairy production systems.
Total bacterial counts were quantified, revealing significant inter-farm variation ( < 0.05) with a range of 3.94-6.68 log CFU/mL. Among 129 bacterial isolates, genus-level dominance and species prevalence were identified. Antimicrobial susceptibility testing (AST) against 10 agents was performed using integrated resistance criteria combining Clinical and Laboratory Standards Institute (CLSI) standards and epidemiological cutoff values (ECOFFs). Nine resistance genes targeting seven antibiotic classes were detected via PCR.
The highest resistance rate was observed for sulfadiazine (53.2%) and the lowest for levofloxacin (6.0%). Multidrug resistance was detected in 23% (20/87) of isolates, with 14 strains meeting ECOFFs-based resistance criteria. PCR analysis showed (70.5%) and (54.3%) as the most prevalent resistance genes, while , (B), and were absent in all isolates. Regional resistance variations correlated significantly with farm management practices.
These findings underscore the impact of historical antibiotic use on AMR dissemination. Enhanced AMR surveillance in raw milk, improved antibiotic stewardship, and targeted interventions are crucial to mitigate public health risks from microbial contamination and horizontal gene transfer of resistance determinants.
本研究系统分析了中国山东省五个奶牛场（n = 30）的散装罐奶中的细菌多样性和抗菌药物耐药性（AMR）概况，以评估与微生物污染相关的公共卫生风险，并为乳制品生产系统的区域质量控制和AMR风险评估提供关键数据。
对总细菌数进行定量，发现农场间存在显著差异（P < 0.05），范围为3.94-6.68 log CFU/mL。在129株细菌分离物中，确定了属水平的优势和物种流行情况。使用结合临床和实验室标准协会（CLSI）标准和流行病学临界值（ECOFFs）的综合耐药标准，对10种药物进行了抗菌药敏试验（AST）。通过PCR检测了针对7类抗生素的9个耐药基因。
磺胺嘧啶的耐药率最高（53.2%），左氧氟沙星的耐药率最低（6.0%）。在23%（20/87）的分离物中检测到多重耐药，其中14株符合基于ECOFFs的耐药标准。PCR分析显示blaTEM（70.5%）和blaCTX-M（54.3%）是最普遍的耐药基因，而blaSHV、mcr-1（B）和mcr-2在所有分离物中均未检出。区域耐药差异与农场管理实践显著相关。
这些发现强调了历史抗生素使用对AMR传播的影响。加强生乳中的AMR监测、改善抗生素管理以及有针对性的干预措施对于减轻微生物污染和耐药决定因素水平基因转移带来的公共卫生风险至关重要。
