Lactobacillus delbrueckii subsp lactis (strain CIDCA 133) resists the antimicrobial activity triggered by molecules derived from enterocyte-like Caco-2 cells.

AIMS

The aim of the present study was to assess the ability of a potentially probiotic strain to resist, in vitro, the effect of intestinal antimicrobial molecules.

METHODS AND RESULTS

Strain CIDCA 133 of Lactobacillus delbrueckii subsp lactis was studied. Lactobacillus delbrueckii subsp bulgaricus as well as other gram-positive and gram-negative bacteria were used for comparison purposes. The effect of different antimicrobial extracts was determined by diffusion assays, viable counts and growth kinetics. Human-defensins (h beta D1 and h beta D2) were also included in the study. Two types of cellular fractions from Caco-2 cells were tested: (i) cytosolic fractions, obtained by sonication of cultured human enterocytes and (ii) cationic fraction, obtained by batch extraction of the cytosolic fraction with a weak cation exchange resin. In addition, the effect of Caco-2-secreted factors was studied. Strain CIDCA 133 was neither inhibited by Caco-2 secreted, cytosolic nor cationic fractions. Of note, human-defensins were inactive against strain CIDCA 133. In contrast, a related lactobacilli: Lactobacilli delbrueckii subsp bulgaricus (strain CIDCA 331) and other species of gram-positive or gram-negative bacteria were strongly inhibited.

CONCLUSIONS

Strain CIDCA 133 is able to survive and grow in the presence of enterocyte-derived antimicrobial molecules. This ability is not a general property of lactobacilli.

SIGNIFICANCE AND IMPACT OF THE STUDY

Results could provide a new insight into the mechanisms of the probiotic effect and encourage further studies on this field. Resistance to antimicrobial peptides can be relevant to understand the interaction of potentially probiotic strains with the host's immune system. This ability can be also relevant as a selection criterion for new probiotic strains.