The aim of this study was to elucidate the anti-pathogenic mechanisms of probiotic bacteria isolated from a commercial preparation which included Lactobacillus gasseri PA 16/8, Bifidobacterium longum SP 07/3 and Bifidobacterium bifidum MF 20/5. The direct anti-pathogenic activity of the probiotics was measured using agar diffusion assays. The ability of the probiotics to produce extra cellular inhibitory factors was also determined by applying fermentation supenatants to indicator lawns in well and disc diffusion assays. Of the eight pathogens and five lactobacilli used as screening organisms there was a low rate of pathogen inhibition. However L gasseri PA 16/8 displayed potential for inhibitory protein production through production of positive amplicons within polymerase chain reaction (PCR) using acido primers.