We investigated the correlation between fecal bacteria composition in early infancy and the prevalence of allergic diseases in late infancy. The fecal microbiota in the first 2 months was profiled using the 16S rRNA V6 short-tag sequences in the community and statistically compared between two groups of subjects who did and did not show allergic symptoms in the first 2 years (n = 11 vs. 11). In the allergic group, genus Bacteroides at 1 month and genera Propionibacterium and Klebsiella at 2 months were more abundant, and genera Acinetobacter and Clostridium at 1 month were less abundant than in the nonallergic group. Allergic infants who showed high colonization of Bacteroides and/or Klebsiella showed less colonization of Clostridium perfringens/butyricum, suggesting antagonism between these bacterial groups in the gastrointestinal tract. It was also remarkable that the relative abundance of total Proteobacteria, excluding genus Klebsiella, was significantly lower in the allergic than in the nonallergic group at the age of 1 month. These results indicate that pyrosequence-based 16S rRNA gene profiling is valid to find the intestinal microbiotal disorder that correlates with allergy development in later life.

Bacterial colonization in infancy is considered crucial for the development of the immune system. Recently, there has been a drastic increase in childhood allergies in Japan. Therefore, we conducted a prospective study with 56 infants on the relationship between gut microbiota in the first year of life and the development of allergies during the first 3 years. In the lactation period, organic acid producers such as Leuconostoc, Weissella and Veillonella tended to be underrepresented in subjects who developed food allergies (FA, n = 14) within the first two years. In the weaning period, children in the FA group were highly colonized by unclassified Enterobacteriaceae and two Clostridium species closely related to Clostridium paraputrificum and C. tertium, and the whole tree phylogenetic diversity index was significantly lower in the FA group. All of these differences in the weaning period were statistically significant, even after adjusting for potential confounding factors. A higher abundance of unclassified Enterobacteriaceae was also found in the other allergic group (n = 15), whereas the two Clostridium species were highly specific to the FA group. The mode of action of these Clostridium species in childhood food allergies remains unknown, warranting further investigation.

The fecal microbiotas were investigated in 13 healthy Thai subjects using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). Among the 186 DNA bands detected on the polyacrylamide gel, 37 bands were identified as representing 11 species: Bacteroides thetaiotaomicron, Bacteroides ovatus, Bacteroides uniformis, Bacteroides vulgatus, Clostridium colicanis, Eubacterium eligenes, E. rectale, Faecalibacterium prausnitzii, Megamonas funiformis, Prevotella copri, and Roseburia intestinalis, belonging mainly to the groups of Bacteroides, Prevotella, Clostridium, and F. prausnitzii. A dendrogram of the PCR-DGGE divided the subjects; vegetarians and non-vegetarians. The fecal microbiotas were also analyzed using a quantitative real-time PCR focused on Bacteroides, Bifidobacterium, Enterobacteriaceae, Clostrium coccoides-Eubacterium rectale, C. leptum, Lactobacillus, and Prevotella. The nonvegetarian and vegetarian subjects were found to have significant differences in the high abundance of the Bacteroides and Prevotella genera, respectively. No significant differences were found in the counts of Bifidabacterium, Enterobacteriaceae, C. coccoides-E. rectale group, C. leptum group, and Lactobacillus. Therefore, these findings on the microbiota of healthy Thais consuming different diets could provide helpful data for predicting the health of South East Asians with similar diets.