Antimicrobial potential of probiotic lactic acid bacteria.

Antibacterial activity is an important characteristic of probiotics. A possible way to achieve this antibacterial activity is through the production of bacteriocins. This study shows that the commercial probiotic strains Lactobacillus johnsonii LA1 and Lactobacillus casei YIT 9029 produce bacteriocins. The nature of the antimicrobial compound could be derived from its behaviour: a narrow inhibitory spectrum (only active against closely related strains), loss of activity when treated with proteinases, and rather small molecular masses (around 6000 Da or less). Further, three bacteriocins produced by Lb. johnsonii LA1, Lb. casei YIT 9029 and Lactobacillus amylovorus DCE 471 showed inhibitory activity against the human gastric pathogen Helicobacter pylori. However, a fourth bacteriocin produced by Lactobacillus acidophilus IBB 801 was not able to inhibit H. pylori. This indicates that some bacteriocins produced by specific probiotic strains can fulfil a role in the inhibition of this common pathogen.