Helicobacter pylori biofilm: a protective environment for bacterial recombination.

Aims: The aim of this work was to investigate the interaction between two Helicobacter pylori strains in promoting genetic transfer, when grown in the biofilm mode. Methods and Results: Biofilms produced by H. pylori 9/10 (A), H. pylori 15/4 (B) and their mixture (C) were studied for biomass production and cell viability. The genetic heterogeneity of 45 clones, coming from mature biofilm of co-cultured H. pylori strains was studied by both RAPD and cagA (EPIYA motifs)/vacA virulence genes analysis. Helicobacter pylori A, B and C developed a well-structured biofilm without significant differences in viability. No significant differences were recorded between A and B biomass measurement, whereas C biofilm expressed a significant (P < 0·001) higher adhesive capability when compared with A and B biofilms. C-clones DNAfingerprintings showed an high genetic heterogeneity (mean similarity value = 0·528). The 60% of C-clones displayed vacA allelic combination s1i1m1m2 associated with cagA EPIYA motif pattern P1P2P3P3P3. Conclusions: Biofilms developed by multiple H. pylori strains are more complex than those associated with single strains. Such condition might promote the genetic exchange favouring the generation of more virulent strains. Significance and Impact of the Study: The ‘biofilm niche’ represents a successful strategy and a suitable environment for promoting bacterial population persistence by recombination events.