Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to provide a scientific opinion on a health claim pursuant to Article 13 of Regulation (EC) No 1924/2006 in the framework of further assessment related to a combination of Lactobacillus rhamnosus CNCM I-1720, Lactobacillus helveticus CNCM I-1722, Bifidobacterium longum subsp. longum CNCM I-3470 and Saccharomyces cerevisiae var. boulardii CNCM I-1079 and defence against pathogenic gastro-intestinal microorganisms. The food constituent that is the subject of the health claim, a combination of L. rhamnosus CNCM I-1720, L. helveticus CNCM I-1722, B. longum subsp. longum CNCM I-3470 and S. cerevisiae var. boulardii CNCM I-1079, is sufficiently characterised. The claimed effect which is proposed for further assessment, defence against pathogenic gastro-intestinal microorganisms, is a beneficial physiological effect. The proposed target population is the general population. No human intervention studies which investigated the effect of a combination of L. rhamnosus CNCM I-1720, L. helveticus CNCM I-1722, B. longum subsp. longum CNCM I-3470 and S. cerevisiae var. boulardii CNCM I-1079 were provided. On the basis of the data presented, the Panel concludes that a cause and effect relationship has not been established between the consumption of a combination of L. rhamnosus CNCM I-1720, L. helveticus CNCM I-1722, B. longum subsp. longum CNCM I-3470 and S. cerevisiae var. boulardii CNCM I-1079 and defence against pathogenic gastro-intestinal microorganisms.