R. Francavilla, C. Fontana & F. Cristofori Department of Pediatrics, University of Bari Aldo Moro, Bari, Italy. E-mail: rfrancavilla@me.com doi:10.1111/j.1365-2036.2012.05010.x Letter: identication of probiotics by specific strain name SIRS, We read with interest the paper by Vandenplas on the efficacy of probiotics vs. placebo for acute gastroenteritis in children. 1 However, more precise informa- tion is needed regarding the strains used. The joint FAO/WHO Expert Consultation 2 recommended that strains be named according to the International Code of Nomenclature, and be deposited in an internationally recognised culture collection to correctly identify the specific strain that is responsible for a given clinical finding. Indeed, it is a well-established fact that the biological effects of probiotics are strain specific, and that the success of a strain cannot be extrapolated to another strain even within the same species. 3 We believe that is important to stress in scientific publications that probiotics should be defined not only by their genus and species, but also and most impor- tantly by the specific strain name. The fact that a bacterium belongs to a specific genus and species (i.e. Lactobacilli rhamnosus) does not alone confer the same properties of a specific strain (L. GG), which may be of critical importance when studying the biological and clinical effects of probiotic bacteria. The authors state that the symbiotic product tested contains several microor- ganisms, for which there is evidence of efficacy in reducing the severity and dura- tion of acute diarrhoea in children such as, L. rhamnosus (formerly LGG). However, it remains unclear if the rhamnosus used in the study is the well- known and characterised LGG, or instead a less titled strain. A simple access to the StrainInfo database (http://www.straininfo.net) shows how numerous are the strains that fall in the genus and species reported in Table 3. 1 It is widely acknowledged that properties from one bacterial strain do not nec- essarily apply to a close relative as strains can differ considerably in genotype and phenotype. 4–6 This is even more important in the case of LGG. Kankainen et al. sequenced and compared the genomes of LGG and a different L. rhamnosus and found that there is a 98% average identity (the same between man and a monkey), however, in the 2% of diversity resides a set of genes (spaCBA) encod- ing three pilin proteins and another gene responsible for the assembly of pilus structures important for colonisation and host interaction. 7 ACKNOWLEDGEMENT Declaration of personal and funding interests: None. REFERENCES 1. Vandenplas Y, De Hert SG; PROBIOTICAL-study group. Randomised clinical trial: the synbiotic food supplement Probiotical vs. placebo for acute gastroenteritis in children. Aliment Pharmacol Ther 2011; 34: 862–7. 2. FAO/WHO (Food and Agriculture Organization/World Health Organisation). Joint FAO/WHO Expert Consultation on Evaluation of Health and Nutritional Properties of Probiotics in Food Including Powder Milk with Live Lactic Acid Bacteria. Cordoba, Argentina, 2001. 3. Azaıïs-Braesco V, Bresson JL, Guarner F, Corthier G. Not all lactic acid bacteria are probiotics, .... but some are. Br J Nutr 2010; 103: 1079–81. 4. Klaenhammer TR, Altermann E, Pfeiler E, et al. Functional genomics of probiotic lactobacilli. J Clin Gastroenterol 2008; 42 (Suppl. 3): S160–2. 5. Coudeyras S, Marchandin H, Fajon C, Forestier C. Taxonomic and strain-specific identification of the probiotic strain Lactobacillus rhamnosus 35 within the Aliment Pharmacol Ther 2012; 35: 852-859 859 ª 2012 Blackwell Publishing Ltd Letters to the Editors