Lactic acid bacteria have been shown to inhibit the growth of pathogenic or disease-causing bacteria and their production of toxins^{4,6,7,10,11,19}. Acidophilus bacteria have a superior capability of producing lactic acid as well as anti-bacteria substances, thus suppressing harmful bacteria ^4,6,7,10.  

B. bifidum particularly protect the body from harmful bacteria by adhering to the intestinal mucosae, by producing acetic acid^4,6,7,10,11, and by activating macrophages, which also produce substances that suppress harmful bacteria^4,6,11. 

L. acidophilus also activates macrophages but its effect is weaker than B. bifiidum ⁶. Yamashita et al¹² found that germ-free subjects orally given Wakunaga's B. bifidum and L. acidophilus in a combination product in conjunction with E. coli suppressed the growth of E. coli.