부산대학교 도서관

Researchers are becoming more interested in studying probiotics at present due to their benefit to human and animal health. In this study, newly isolated strains from human feces were evaluated for probiotic properties. A total of sixty isolated strains were collected from feces and six out of sixty isolated strains could inhibit the growth of Salmonella typhi and Salmonella typhimurium. The strain which gave the best inhibitory effect was selected for further characterization as a probiotic strain. The identification of this strain was analyzed on the basis of morphological and biochemical characteristics and 16S rDNA gene sequence. This strain was Gram-positive, rod shaped, and catalase and oxidase-negative, and produced acids from D-glucose, D-fructose, lactose, mannitol, sorbitol, inulin and starch. It could not hydrolyze esculin or red blood cells. Based on its 16S rDNA gene sequence, it was Lactobacillus salivarius, and so was called L. salivarius MTC 1026 in this study, and was closely related with L. salivarius DSPV 344T isolated from the calf gut. It was able to survive in gastric and small intestinal juices at pH 2.0 and 1.0% bile salt for several hours and also could grow at 45°C. Moreover, this strain showed inhibitory activity against a variety of food-borne pathogens. It was highly sensitive to piperacillin, chloramphenicl, ampicillin, erythromycin and ceftazidime. After plasmid curing, this strain was susceptible to gentamicin, amikacin, norfloxacin and ciprofloxacin. L. salivarius MTC 1026 could significantly inhibit the adhesion process of E. coli ATCC 25922 and S. typhimurium ATCC 13311 on Caco-2 monolayers in a competition assay and also reduced invasion of both pathogens (4-log cfu/ml) in an exclusion and displacement assay. Therefore, it was clearly demonstrated in this study that L. salivarius MTC 1026 has shown promising properties as a candidate for a potential probiotic for applications in humans and animals.