Helicobacter pylori inhibition by probiotic lactobacilli has been observed in vitro and in vivo. Carefully selected probiotic Lactobacillus strains could therefore play an important role in the treatment of H. pylori infection and eradication. However, the underlying mechanism for this inhibition is not clear. The aim of this study was to examine if peptide extracts, containing bacteriocins or other antibacterial peptides, from six Lactobacillus cultures (Lactobacillus acidophilus La1, Lactobacillus amylovorus DCE 471, Lactobacillus casei YIT 9029, Lactobacillus gasseri K7, Lactobacillus johnsonii La1, and Lactobacillus rhamnosus GG) contribute to the inhibition of H. pylori. Peptide extracts from cultures of Lact. amylovorus DCE 471 and Lact. johnsonii La1 were most active, reducing the viability of H. pylori ATCC 43504 with more than 2 log units within 4 h of incubation (P < 0.001). The four other extracts were less or not active. When six clinical isolates of H. pylori were tested for their susceptibility towards five inhibitory peptide extracts, similar observations were made. Again, the peptide extracts from Lact. amylovorus DCE 471 and Lact. johnsonii La1 were the most inhibitory, while the three other extracts resulted in a much lower inhibition of H. pylori. Protease-treated extracts were inactive towards H. pylori, confirming the proteinaceous nature of the inhibitory substance.

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