A probiotic containing the bacterium Lactobacillus acidophilus with potential antimicrobial and immunomodulatory activities. As a dietary supplement, Lactobacillus acidophilus (L. acidophilus), a naturally-occurring bacteria, may improve digestion and help maintain adequate colonization of the gastrointestinal (GI) tract by modulating the composition of the normal microflora. Because it produces lactic acid and hydrogen peroxide and other substances during fermentation, this bacterium creates an acidic environment unfavorable to pathogens such as Candida albicans. In addition, during colonization of the GI tract, L. acidophilus may form a protective barrier, preventing attachment of pathogens. Dietary supplementation with this bacterium has been shown to enhance natural and acquired immunity in mice.