1 Department of Animal Science, The University of Tennessee , Knoxville, Tennessee.
2 Department of Food Science, The University of Tennessee , Knoxville, Tennessee.
Foodborne Pathog Dis. 2018 Jul;15(7):449-458. doi: 10.1089/fpd.2017.2362. Epub 2018 Feb 2.
Staphylococcus aureus is a frequent and major contagious mastitis bacterial pathogen. The antibiotic treatment cure rates vary considerably from 4% to 92%. Staphylococcus aureus readily becomes resistant to antibiotics, resulting in persistent noncurable intramammary infection that usually results in culling of infected animals. Because of its notorious ability to acquire resistance to the commonly used as well as last resort antimicrobials such as methicillin and vancomycin and the development of multidrug-resistant strains, antimicrobial resistance (AMR) in S. aureus is of paramount importance in human medicine. The objective of this study was to evaluate the prevalence of AMR and genetic diversity of S. aureus isolates from milk of dairy cattle. Staphylococcus aureus isolates (n = 239) from 33 dairy farms in Tennessee were tested against 10 antimicrobials by broth microdilution method using the Sensititer system. Genetic diversity of resistant isolates was evaluated by pulsed-field gel electrophoresis (PFGE). Overall, AMR of the S. aureus isolates varied from as low as 1.3% for ceftiofur to as high as 25% for sulfadimethoxine. Out of 239 S. aureus isolates, 82 (34.3%) of them were resistant to at least 1 of the 10 antimicrobials. The AMR isolates belonged to two major PFGE types, indicating the presence of dominant clonal patterns among the resistant isolates. In general, there was a variation of prevalence of AMR within and among farms over time, with an increasing trend in tetracycline resistance. Judicious use of antimicrobials in dairy cattle farms can reduce the development of antimicrobial-resistant S. aureus.
金黄色葡萄球菌是一种常见且主要的传染性乳腺炎细菌病原体。抗生素治疗的治愈率差异很大，从 4%到 92%不等。金黄色葡萄球菌很容易对抗生素产生耐药性，导致持续性无法治愈的乳腺炎感染，通常导致受感染动物被淘汰。由于其臭名昭著的获得对常用抗生素甚至最后手段抗生素（如甲氧西林和万古霉素）的耐药性的能力，以及多药耐药菌株的发展，金黄色葡萄球菌的抗生素耐药性（AMR）在人类医学中至关重要。本研究旨在评估田纳西州 33 个奶牛场的牛奶中金黄色葡萄球菌分离株的 AMR 流行率和遗传多样性。使用 Sensititer 系统通过肉汤微量稀释法对来自田纳西州 33 个奶牛场的 239 株金黄色葡萄球菌分离株进行了 10 种抗生素的测试。通过脉冲场凝胶电泳（PFGE）评估耐药分离株的遗传多样性。总体而言，金黄色葡萄球菌分离株的 AMR 从头孢噻呋的低至 1.3%到磺胺二甲氧嘧啶的高至 25%不等。在 239 株金黄色葡萄球菌分离株中，有 82 株（34.3%）至少对 10 种抗生素中的 1 种耐药。AMR 分离株属于两种主要的 PFGE 类型，表明耐药分离株中存在优势克隆模式。一般来说，AMR 的流行率在农场内部和之间随时间变化，四环素耐药性呈上升趋势。在奶牛场合理使用抗生素可以减少抗药性金黄色葡萄球菌的发展。
