LETTER Influence of probiotic administration on the fecal microbiota in diarrhea-predominant irritable bowel syndrome C. Subramanyam 1 & Nitesh Pratap 1 & Prasad Gandham 1 & Rupjyothi Talukdar 1 & M. Sasikala 1 & H. V. V. Murthy 1 & D. Nageshwar Reddy 1 # Indian Society of Gastroenterology 2015 There is a growing interest in the role of altered gastro- intestinal (GI) microbiota in the pathogenesis of irritable bowel syndrome (IBS) [1]. Qualitative and quantitative changes in GI microbiota contributing to increased pro- duction of proinflammatory cytokines, organic acids, and gases (H 2 , CH 4 and CO 2 ) have earlier been reported to alter water and electrolyte balance in the GI tract causing diarrhea-related symptoms in IBS [ 2 , 3 ]. Recent reports on the beneficial effects of probiotic ad- ministration in IBS, by suppressing formation of proin- flammatory cytokines and protecting the integrity of in- testinal barrier functions, indicate that normalizing GI microbiota can be a useful strategy in the management of IBS [4]. In order to examine alterations in GI micro- biota in diarrhea-predominant IBS (IBS-D) and to eval- uate the beneficial effect of probiotic administration in such cases, we analyzed and compared fecal microbiota in Indian patients with IBS-D (n =10) and healthy con- trols (n =10), apart from examining changes in fecal microbiota in IBS-D patients after administration of a multistrain probiotic (VSL#3). Following an 8-week washout period without antibiotics, anti-inflammatory drugs, and probiotics, IBS-D patients were given one capsule of VSL#3 containing 112.5 billion CFU of ly- ophilized bacteria (four strains of Lactobacillus [ Lactobacillus paracasei DSM 24733, Lactobacillus plantarum DSM 24730, Lactobacillus acidophilus DSM 24735, and Lactobacillus delbrueckii subsp. bulgaricus DSM 24734], three strains of Bifidobacterium [Bifidobacterium longum DSM 24736, Bifidobacterium infantis DSM 24737, and Bifidobacterium breve DSM 24732], and one strain of Streptococcus [ Streptococcus thermophilus DSM 24731]) twice a day for 8 weeks. DNA was isolated from fresh fecal samples collected from IBS-D patients before and after 8-week consumption of the probiotic as well as from age-matched healthy controls and sub- jected to PCR amplification of the V3 region of 16S ribosomal RNA (rRNA) using forward (338F 5′ACTC CTACGGGAGGCAGCAG 3′ ) and reverse (533R 5′ TTACCGCGGCTGCTGGCAC3′) primers. Libraries of 16S rRNA genes were constructed according to the TruSeq DNA library protocol followed by sequencing on Illumina Genome Analyzer I and sequence cluster- ing into operational taxonomic units (OTUs) based on their sequence similarity. The QIIME pipeline was employed to compare microbial communities. Results depicted in Fig. 1 indicate community level dysbiosis of different bacterial groups in IBS-D. Fecal microbiota in patients with IBS-D contained higher percentage abundance (14-fold) of Fusobacteria, concomitant with marked decrease (4.0 % to 6.5 %) in probiotic genera (Lactobacillus and Bifidobacterium) in comparison to healthy controls. Such dysbiosis was mitigated to a marked extent after administration of VSL#3. It is pos- sible that the ultimate effects of Fusobacterial infection in the gut may be a consequence of the microbes with which this species aggregates. Thus, it is reasonable to assume that the community level dysbiosis of GI mi- crobiota observed in IBS-D would promote enhanced growth of potentially harmful members of this phylum. * C. Subramanyam aigres.cs@gmail.com 1 Department of Basic Sciences, Asian Institute of Gastroenterology, 6-3-661, Somajiguda, Hyderabad 500 082, India Indian J Gastroenterol DOI 10.1007/s12664-015-0545-8