In vitro selection criteria for probiotic bacteria of human origin: correlation with in vivo findings

Abstract

The enteric flora comprises approximately 95% of the total number of cells in the human body and can elicit immune responses while protecting against microbial pathogens. However, the resident bacterial flora of the gastrointestinal tract may also be implicated in the pathogenesis of diseases such as inflammatory bowel disease (ulcerative colitis and Crohn disease). The objectives of the Probiotic Research Group based at University College Cork were to isolate and identify lactic acid bacteria exhibiting beneficial probiotic traits, such as bile tolerance in the absence of deconjugation activity, acid resistance, adherence to host epithelial tissue, and in vitro antagonism of pathogenic microorganisms or those suspected of promoting inflammation. To isolate potentially effective probiotic bacteria, we screened the microbial population adhering to surgically resected segments of the gastrointestinal tract (the environment in which they may subsequently be reintroduced and required to function). In total, 1500 bacterial strains from resected human terminal ilea were assessed. From among these organisms, Lactobacillus salivarius subsp. salivarius strain UCC118 was selected for further study. In mouse feeding trials, milk-borne L. salivarius strain UCC118 could successfully colonize the murine gastrointestinal tract. A human feeding study conducted in 80 healthy volunteers showed that yogurt can be used as a vehicle for delivery of strain UCC118 to the human gastrointestinal tract with considerable efficacy in influencing gut flora and colonization. In summary, we developed criteria for in vitro selection of probiotic bacteria that may reflect certain in vivo effects on the host such as modulation of gastrointestinal tract microflora.

Curd Lactobacilli with Probiotic Potentiality

“…Probiotic lactobacilli are required to pass through the highly acidic gastric condition of the stomach in order to reach the intestine for residence and functioning, and hence such strains must be tolerant to low-pH conditions of the stomach and resistant to intestinal bile salts for their survival in the digestive system, because viability and activity are important considerations of microorganisms to be the probiotics [22]. The physiological concentration of human bile salts ranges 0.3-0.5% [23,24]. Considering bile tolerance an important characteristic of probiotic microorganisms, it has been reported that 0.3% oxgall closely appropriates the bile level of the human gastrointestinal tract, and the concentration of 0.3% bile salts has been considered crucial for screening and selection of human probiotics [25,26].…”

Identification and characterization of Bacillus subtilis from grass carp (Ctenopharynodon idellus) for use as probiotic additives in aquatic feed

“…Adhesions to intestinal epithelial cells and mucus are frequently estimated to select and assess probiotic bacteria [28]. In this study, the adhesions of the vegetative cells and spores of the B. subtilis isolates to Caco-2 cells and intestinal mucus were examined by SEM observation and adhesive capacity analyses (Fig.…”

A Randomised Controlled Trial of a Probiotic Lactobacillus Strain in Healthy Adults: Assessment of its Delivery, Transit and Influence on Microbial Flora and Enteric Immunity

“…These approaches resulted in the isolation of Lactobacillus strains from healthy human adults (20,21) and their subsequent assessment in murine models (22). In this study, our objective was to further characterise the probiotic Lactobacillus salivarius strain U CC118 and to focus speci cally upon: (i) effective delivery of the probiotic micro-organism to the human gut using fermented and non-fermented delivery vehicles; (ii) evaluation of the ability of the strain to survive transit through (and persist within) the human intestinal tract; (iii) accepting the complexity of the hostile intestinal and faecal environments, assessment of a method of enumerating the introduced bacterial strain using conventional microbiological techniques; (iv) determining the effect of probiotic consumption on the numbers of faecal-borne selected indigenous bacteria; and (v) evaluation of immune recognition of the consumed probiotic bacteria.…”