Bovine enteric bacterial pathogens are a major cause of health decline in agricultural cattle populations. The identification of host-derived microbiota with probiotic characteristics is key for the development of treatments utilizing pathogen displacement and recolonization by commensal flora. In this study, intestinal microbiota in fecal samples from four Holstein dairy cows were analyzed using 16S ribosomal RNA gene next-generation sequencing, leading to the identification of three Lactobacillus isolates (Lactobacillus gasseri, Lactobacillus reuteri, and Lactobacillus salivarius). By taking advantage of the preferential growth in acidified culture media, bacterial characteristics examination, and restriction fragment length polymorphism analysis of 16S rRNA genes, the three lactic acid bacteria (LAB) strains were successfully isolated. The three LAB isolates possess the prerequisite growth tolerances for probiotic functionality, as well as exhibit effective antimicrobial potency against enteric bacterial pathogens of cattle, including Escherichia coli O157:H7, Mycobacterium avium subspecies paratuberculosis, and Salmonella species (Salmonella enteritidis, Salmonella typhimurium, and Salmonella Dublin). Moreover, the LAB isolates showed significant adhesion to cattle intestine, implying greater survivability potential due to their species specificity when administered in the same host species. The LAB isolates were sensitive to most antibiotics with notable resistances of L. gasseri to streptomycin and L. salivarius to kanamycin. Genes attributed to specific antibiotic resistances demonstrated a low risk of lateral transfer in a conjugation study. Our in vitro results demonstrate the promising probiotic characteristics of these newly identified Lactobacillus strains and their considerable potential to serve as probiotics feed supplements for cows.

中文翻译：

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从奶牛粪便中分离出的自生乳酸菌具有良好的益生菌特性和对牛食源性病原菌的体外抗菌活性。

牛肠细菌病原体是造成农业牛群健康下降的主要原因。鉴定具有益生菌特征的宿主来源的微生物群是开发利用病原体置换和共生菌群重新定殖的治疗方法的关键。在这项研究中，使用16S核糖体RNA基因下一代测序技术分析了四头荷斯坦奶牛粪便样品中的肠道菌群，从而鉴定出了三种乳酸杆菌菌株（加氏乳杆菌，路透氏乳杆菌和唾液乳杆菌）。通过利用在酸性培养基中的优先生长，细菌特征检查和16S rRNA基因的限制性片段长度多态性分析，成功分离了三种乳酸菌（LAB）菌株。这三种LAB分离株具有益生菌功能性的前提条件，并且对牛的肠细菌病原体（包括大肠杆菌O157：H7，鸟分枝杆菌亚种，结核分枝杆菌和沙门氏菌（肠炎沙门氏菌，鼠伤寒沙门氏菌和都柏林沙门氏菌）。此外，LAB分离株对牛肠表现出显着的粘附性，这意味着由于它们在相同宿主物种中给药时的物种特异性，因此具有更大的生存潜力。LAB分离株对大多数抗生素敏感，而加氏乳杆菌对链霉素和唾液乳杆菌对卡那霉素具有显着耐药性。在结合研究中，归因于特定抗生素抗性的基因显示出横向转移的低风险。