addition to characterize the dominant microbiota in infancy, we looked forward to anunderstanding of the relationships between the intestinal microbiota and disease develop-ment. By enrolling twin pairs (n=14) in our study, we found a difference in bacterial familiesof intestinal microbiota composition (0-12 months) existed in dizygotic twins although theylived in the same environment. Among infants from twin (n=14) or singleton (n=7) pregnancy,the initial colonizer was restricted to bacteria from Proteobacteria (Escherichia/Shigella orSphingopyxis) and Firmicutes (Bacillus or Staphylococcus). During the study period, 52.4%of these subjects developed allergic symptoms, mainly nasal and skin manifestations. Mostimportantly, we found a distinctive feature of gut microbiota pattern in allergic infants (n=11) as compared with the healthy babies (n=10). The former harbored relative abundanceof Firmicutes bacteria, particularly those from families Clostridiaceae and Lachnospiraceaeof Firmicutes. Increasing Clostridiaceae in allergic subjects (72.7%) was observed from 1stto 6th month after birth, and thereafter declined gradually to an undetectable level at 12thmonth ; whereas the presence of Clostridiaceae in healthy babies was maintained in lowfrequency from 1st to 12th months (p<0.01). On the other hand, rapid growth of Lachnospira-ceae bacteria in allergic infants (63.6%) started from 6th month to 12th month, while thispattern was rarely found in healthy control subjects (10%; p<0.01). In addition, reducedcolonization of Bifidobacteriaceae was found apparently in allergic subjects, as comparedwith that of controls (p<0.05). In conclusion, our observation confirmed the link betweengut micorbiota patterns and the risk of allergy development. This link may provide somehints for future therapeutic strategies. (Grant Taiwan NSC102-2628-B-002 -027 -MY3 )

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Decreased Diversity of the Fecal Microbiome in Pediatric Carriage ofClostridium difficileSuchitra Hourigan, Zoya Grigoryan, SuBin Kim, Sankar Chirumamilla, ShervinRabizadeh, Jonathan Golub, Shehzad A. Saeed, Charles O. Elson, Maria Oliva-Hemker,Cynthia L. Sears, Martin Blaser, Lea Ann Chen

Background: Certain populations have increased rates of asymptomatic carriage of Clostridiumdifficile (C. difficile), such as patients with inflammatory bowel disease and young children.There is decreased diversity and compositional changes of the fecal microbiome in patientswith recurrent C. difficile disease. However the diversity of the fecal microbiome in thosewith asymptomatic carriage has not previously been investigated. Methods: Stool sampleswere tested from a previously collected fecal bank from pediatric gastroenterology patients(mean age 12.5 ± 4.3 yrs, range 4-21yrs) at two large academic medical centers. Many ofthese patients were being evaluated or treated for IBD, a risk factor for C. difficile; no patienthad exposure to concurrent antibiotics. Toxigenic C. difficile testing was performed on stoolsamples by selective anaerobic culture and cytotoxic assay. All C. difficile testing was performedfor non-clinical indications. The v4 hypervariable region of the 16S rRNA gene was sequencedusing the Illumina MiSeq platform. 2x250 bp paired end reads were generated. De-multi-plexed sequences were filtered for quality and clustered into operational taxonomical units(OTUs) using QIIME 1.7.0 software and the May 2013 Greengenes 16S reference. Alphararefaction and taxa plots were generated using QIIME software. Results: At all sequencingdepths, patients without C. difficile carriage had significantly increased bacterial diversitycompared to C. difficile positive patients. This relationship is consistent for rarefaction curvesusing both observed species and Chao1 metrics for estimating alpha diversity. Taxa plotsdemonstrate an increase in the relative abundance of the phylum Proteobacteria in C. difficilenegative patients (6.1% vs. 0.3%), which consists largely of bacteria from the Enterobacterialesorder. Interestingly, the C. difficile positive patients carry relatively fewer bacteria from theClostridiales order. Genus level data further reflect the decreased bacterial diversity seen inC. difficile positive patients. Clostridium spp and similarly related organisms contributed aminute fraction of the overall bacterial composition of both C. difficile positive and negativepatients. Conclusions: Pediatric patients with C. difficile carriage have decreased bacterialdiversity compared to C. difficile negative patients. These data suggest that C. difficile coloniza-tion is sufficient to reduce microbiota diversity and that reduced diversity is not necessarilya hallmark of disease. Although the microbiota of C. difficile positive and negative patientsare largely similar on higher taxonomic (phylum) levels, genus level data are more reflectiveof the microbiome differences between these two groups.

S-13 AGA Abstracts

Taxa plot based on Clostridium difficile status

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Murine Weanling Undernutrition Reveals Sexual Dimorphisms in WeightFaltering, Small Intestinal Transcriptome, and DysbiosisSean R. Moore, Elizabeth A. Maier, Geoffrey A. Preidis, Toni-Ann Mistretta, Emily B.Hollister, Tor Savidge, Michael A. Helmrath, Ernest Fischer, Yael Haberman, Lee Denson

Background: Early weaning of infants in low- and middle-income countries to multideficientdiets leads to profound deficits in children's growth and neurodevelopment. For reasonspoorly understood, male children under 5 years of age are more likely than females to becomeunderweight and stunted in these settings. We sought to mimic this sexual dimorphism inmice and test the hypothesis that gender influences gut transcriptome and microbiomeresponses to undernutrition. Methods: C57BL/6 dams with 10-day-old pups were random-ized to ad lib access to a standard purified control diet (CD; 65% carbohydrate, 20% protein,15% fat) or an isocaloric, multideficient regional basic diet (RBD; 88% carbohydrate, 7%protein, 5% fat) we have previously shown produces features of environmental enteropathyin mice (Ueno AJP 2011). On day of life 21, suckling pups were weaned to their dams' dietand segregated by sex. Upon sacrifice at 6 weeks of age, we harvested jejunal segments forRNA-seq analysis and stool for 16s rRNA analysis. Results: Suckling male and female RBDmice exhibited significant failure to thrive (P<.0001). At weaning, we detected no sex-specific differences in weight; however, by 6 weeks of age we observed that RBD femalesachieved weight parity with CD females, while RBD males remained 25% underweightrelative to CD males (P<.0001). Interestingly, RBD males remained underweight at 12 weeksof age, even when weaned to CD. RNA-seq analysis of jejunal segments (n=3 mice pergroup) revealed 7 transcripts with ≥2-fold differential expression between male vs. femaleCD mice, 97 transcripts between RBD vs. CD males, and a remarkable 3667 transcriptsbetween RBD vs. CD females. Microbiome analysis of stool revealed a more profound(ANOVA Q<.05 for 18 vs. 14 of 96 genera) and homogenous (principle component analysis)shift in microbial communities in female vs. male RBD mice, respectively. Several notablegenera were significantly altered in stool from 6-week RBD mice compared to controls.Alistipes and E. coli/Shigella were increased in males. Alistipes was also increased in females,although E. coli/Shigella was notably not detected. Akkermansia, Clostridium XlV, Barnesiella,and Sporobacter were reduced in females, whereas Parasutterella and Allobaculum were moreabundant. Conclusions: Male mice exhibit more severe growth faltering than females inresponse to early undernutrition, thus mimicking growth patterns seen among children inlow-resource settings. Further studies are needed to determine whether a more robusttranscriptional-microbiome program in the female gut enhances energy harvest in the settingof undernutrition. Such studies, in turn, may provide novel strategies to reduce an unaccepta-bly high burden of childhood undernutrition in the developing world.

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Fecal Metabolomics Distinguishes Responders From Non-Responders to aDietary Intervention in Children With Irritable Bowel SyndromeBruno P. Chumpitazi, Emily B. Hollister, James Versalovic, Tor Savidge, Robert J. Shulman

Background: In a small pilot study we previously demonstrated that children with irritablebowel syndrome (IBS) had a decrease in GI symptom severity (e.g. abdominal pain frequency)when placed on a low fermentable substrate diet (LFSD). We also demonstrated that Respond-ers (decrease in abdominal pain frequency ≥50%) had a different microbiome compositionas compared to Non-Responders. The current study sought to determine whether fecalmetabolites also could distinguish Responders from Non-Responders to the LFSD. Methods:Children (n=8) with pediatric Rome III defined IBS completed a 7-d baseline habitual dietperiod followed by a 7-d LFSD. Stool samples from the baseline and LFSD interventionperiod had previously been analyzed for each subject for microbiome composition using16S rRNA pyrosequencing with determination of operational taxonomic units (OTUs). Inthe current study the same stool samples were used for fecal metabolite characterization.Stool samples were divided into 3 fractions: 1 for analysis by ultra-performance liquidchromatography tandem mass spectroscopy (UPLC/MS/MS2; positive mode), 1 for UPLC/MS/MS2 (negative mode), and 1 for gas chromatography mass spectroscopy (GC/MS). Rawdata were extracted, peak-identified, and processed using proprietary hardware and software.Differences in stool metabolites between Responders and Non-responders at baseline andduring the LFSD were evaluated using repeated measures ANOVA. Potential relationshipsbetween OTUs identified in our previous study and metabolites identified in this study wereevaluated using an all vs. all Spearman correlation of OTUs and metabolites, followed byBenjamin-Hochberg corrections for multiple comparisons in R. Subject -OTU-metaboliterelationships were visualized using a hive plot approach. Results: At baseline, 22 fecalmetabolites differed between Responders and Non-Responders at the P<0.05 level. Duringthe LFSD, 39 fecal metabolites, including Isovalerate, citrulline, D-urobilin, and cholate

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