[Influence of Lactobacillus casei on biofilm formation by enteroaggregative Escherichia coli strains isolated from irritable bowel syndrome (IBS)].

Introduction: Many pathogenic bacterial species have the ability to biofilm formation. In our study we determined the influence of Lactobacillus casei on biofilm formation by enteroaggregative Escherichia coli (EAEC) strains obtained from irritable bowel syndrome patients.

Methods: The ability of EAEC isolates to biofilm formation was assessed in the presence of various concentrations of the probiotic L. casei strain in an a semi- quantitative microtitre plate assays under culture conditions, similar to those prevailing in the human intestine.

Results: Depending on the concentrations L. casei inhibited biofilm formation of the majority (> 80%) of the EAEC strains. Concentration of 4.5 x 10(7) cfu/ml of L. casei was the most effective inhibitory dose, although a few strains (approximately 18%) formed the biofilm regardless of the presence and concentration of the probiotic L. casei strain.

Conclusion: The inhibitory effect of L. casei on biofilm formation at most of studied EAEC strains suggest that L. casei may reduce the risk of developing persistent intestinal infections in humans.