Probiotics: from myth to reality. Demonstration of functionality in animalmodels of disease and in human clinical trials

The enteric flora comprise approximately 95% of the total number of cells i n the human body and are capable of eliciting immune responses while also p rotecting against microbial pathogens. However, the resident bacterial flor a of the gastrointestinal tract (GIT) may also be implicated in the pathoge nesis of several chronic conditions such as inflammatory bowel disease (IBD ). The University College Cork-based Probiotic Research Group has successfu lly isolated and identified lactic acid bacteria (LAB) which exhibit benefi cial probiotic traits. These characteristics include the demonstration of b ile tolerance; acid resistance; adherence to host epithelial tissue; and in vitro antagonism of potentially-pathogenic micro-organisms or those which have been implicated in promoting inflammation. The primary objective of th is report is to describe the strategy adopted for the selection of potentia lly effective probiotic bacteria. The study further describes the evaluatio n of two members of the resulting panel of micro-organisms (Lactobacillus s alivarius subsp. salivarius UCC118 and Bifidobacterium longum infantis 3562 4) under in vitro conditions and throughout in vivo murine and human feedin g trials. Specifically, an initial feeding study completed in Balb/c mice f ocused upon (i) effective delivery of the probiotic micro-organisms to the GIT and evaluation of the ability of the introduced strains to survive tran sit through, and possibly colonise, the murine GIT; (ii) accepting the comp lexity of the hostile GIT and faecal environments, development of a method of enumerating the introduced bacterial strains using conventional microbio logical techniques; and (iii) assessment of the effects of administered bac terial strains on the numbers of specific recoverable indigenous bacteria i n the murine GIT and faeces. Additional research, exploiting the availabili ty of murine models of inflammatory bowel disease, demonstrated the benefic ial effects of administering probiotic combinations of Lactobacillus saliva rius UCC118 and Bifidobacterium longum infantis 35624 in prevention of illn ess-related weight loss. A further ethically-approved feeding trial, succes sfully conducted in 80 healthy volunteers, demonstrated that yoghurt can be used as a vehicle for delivery of Lactobacillus salivarius strain UCC118 t o the human GIT with considerable efficacy in influencing gut flora and col onisation.