| Summary: | 碩士 === 國立中興大學 === 獸醫學系暨研究所 === 105 === Probiotics are defined as live microorganisms which provide health benefits to the host by altering indigenous microbiota, pre¬venting infections, and stimulating the host’s immune system when ad¬ministered in adequate amounts. Currently, the most widely used probiotics include lactic acid bacteria, specifically Lactobacillus and Bifidobacterium species.
In this study, feces of four healthy Holstein dairy cows were collected from rectum and fecal bacterial microbiota were analyzed by next-generation sequencing (NGS) technology whereby three Lactobacillus strains, including Lactobacillus gasseri (L. gasseri), Lactobacillus reuteri (L. reuteri), and Lactobacillus salivarius (L. salivarius) were identified. Three targeted Lactobacillus strains in the fecal samples were primarily screened by selected medium (de Man, Rogosa and Sharpe; MRS) and gram stain. Subsequently, computer-simulated restriction fragment length polymorphism (RFLP) analysis was applied to distinguish individual strains. Combined with 16S rDNA gene sequencing, three targeted Lactobacillus strains were successfully isolated from the fecal samples and then subjected to assess their probiotic properties, such as tolerance of pH, bile, and simulated gastric and intestinal fluids. As to their antibacterial activities, all isolates supernatant exhibited antagonistic effects toward Escherichia coli O157:H7, Salmonella enteritidis, Salmonella enterica serotype Typhimurium, and Mycobacterium avium subsp. paratuberculosis K-10.
In conclusion, three Lactobacillus strains isolated from cow manure showed antimicrobial activity against four enteric pathogens of dairy cows, which may serve as potential probiotic candidates. The efficacy of probiotics treatment and prevention of gastrointestinal microbial dysbiosis can be further confirmed by the in vivo studies.
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