Aperce C C, Amachawadi R, Van Bibber-Krueger C L, Nagaraja T G, Scott H M, Vinasco-Torre J, Drouillard J S
Departments of Animal Sciences and Industry, Kansas State University, Manhattan, Kansas, United States of America.
Diagnostic Medicine and Pathobiology, Kansas State University, Manhattan, Kansas, United States of America.
PLoS One. 2016 Dec 28;11(12):e0168983. doi: 10.1371/journal.pone.0168983. eCollection 2016.
The pool of antimicrobial resistance determinants in the environment and in the gut flora of cattle is a serious public health concern. In addition to being a source of human exposure, these bacteria can transfer antibiotic resistance determinants to pathogenic bacteria and endanger the future of antimicrobial therapy. The occurrence of antimicrobial resistance genes on mobile genetic elements, such as plasmids, facilitates spread of resistance. Recent work has shown in vitro anti-plasmid activity of menthol, a plant-based compound with the potential to be used as a feed additive to beneficially alter ruminal fermentation. The present study aimed to determine if menthol supplementation in diets of feedlot cattle decreases the prevalence of multidrug-resistant bacteria in feces. Menthol was included in diets of steers at 0.3% of diet dry matter. Fecal samples were collected weekly for 4 weeks and analyzed for total coliforms counts, antimicrobial susceptibilities, and the prevalence of tet genes in E. coli isolates. Results revealed no effect of menthol supplementation on total coliforms counts or prevalence of E. coli resistant to amoxicillin, ampicillin, azithromycin, cefoxitin, ceftiofur, ceftriaxone, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, sulfisoxazole, and sulfamethoxazole; however, 30 days of menthol addition to steer diets increased the prevalence of tetracycline-resistant E. coli (P < 0.02). Although the mechanism by which menthol exerts its effects remains unclear, results of our study suggest that menthol may have an impact on antimicrobial resistance in gut bacteria.
环境及牛肠道菌群中的抗微生物耐药性决定因素库是一个严重的公共卫生问题。这些细菌除了是人类接触抗微生物药物的来源外，还可将抗生素耐药性决定因素转移至病原菌，危及抗微生物治疗的未来。存在于质粒等可移动遗传元件上的抗微生物耐药基因促进了耐药性的传播。最近的研究表明，薄荷醇具有体外抗质粒活性，这种植物性化合物有潜力用作饲料添加剂，有益地改变瘤胃发酵。本研究旨在确定育肥牛日粮中添加薄荷醇是否会降低粪便中多重耐药菌的流行率。将薄荷醇按日粮干物质的0.3%添加到阉牛日粮中。每周采集粪便样本，持续4周，分析总大肠菌群计数、抗微生物敏感性以及大肠杆菌分离株中tet基因的流行率。结果显示，添加薄荷醇对总大肠菌群计数或对阿莫西林、氨苄西林、阿奇霉素、头孢西丁、头孢噻呋、头孢曲松、氯霉素、环丙沙星、庆大霉素、卡那霉素、萘啶酸、链霉素、磺胺异恶唑和磺胺甲恶唑耐药的大肠杆菌流行率没有影响；然而，在阉牛日粮中添加30天薄荷醇会增加四环素耐药大肠杆菌的流行率（P<0.02）。虽然薄荷醇发挥作用的机制尚不清楚，但我们的研究结果表明，薄荷醇可能会对肠道细菌的抗微生物耐药性产生影响。
