Following a request from the European Commission, the Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to provide a scientific opinion on health claims pursuant to Article 13 of Regulation (EC) No 1924/2006 in the framework of further assessment. This opinion addresses the scientific substantiation of health claims related to microorganisms for which the Panel considered in previous opinions that the data provided were not sufficient to characterise the microorganisms in question. The criteria used by the Panel for the characterisation of food constituents that are bacteria and combinations thereof, which are the subject of health claims, are: species identification by DNA-DNA hybridisation or 16S rRNA gene sequence analysis and/or sequence analysis of other relevant genetic markers; strain identification by DNA macrorestriction followed by pulsed-field gel electrophoresis, randomly amplified polymorphic DNA analysis, or other internationally accepted genetic typing molecular methods. Only when these two criteria are fulfilled is the bacterium considered to be sufficiently characterised. In the case of combinations of several bacteria, the Panel considers that if one microorganism used in the combination is not sufficiently characterised, the combination proposed is not sufficiently characterised. The Panel considers that the food constituents which are the subject of this opinion are not sufficiently characterised. On the basis of the data presented, the Panel concludes that a cause and effect relationship cannot be established between the consumption of the food constituents which are the subject of this opinion and the claimed effects.