Effect of the oral intake of yogurt containing Bifidobacterium longum BB536 on the cell numbers of enterotoxigenic Bacteroides fragilis in microbiota.

Enterotoxigenic Bacteroides fragilis (ETBF) strains have been suggested to be associated with acute and persistent diarrheal disease, inflammatory bowel disease and colorectal cancer, although further epidemiological studies are needed for clarification. Here, a pilot study was performed to examine the effect of the oral administration of yogurt supplemented with a probiotic strain on the cell numbers of fecal ETBF in a healthy population. Among 420 healthy adults, 38 subjects were found to be ETBF carriers, giving a prevalence of approximately 9%. Among them, 32 subjects were enrolled in an open, randomized, parallel-group study to ingest yogurt supplemented with a probiotic strain, Bifidobacterium longum BB536 (BB536Y group), for 8 weeks, with milk provided to the control group (milk group). The cell numbers of ETBF and the dominant species of the B. fragilis group were measured by a quantitative PCR method. Compared with the baseline values, there was a significant decrease in the cell number of ETBF at week 8 in the BB536Y group but not in the milk group. Linear mixed models analysis for longitudinal data revealed a significant difference in the changes of ETBF cell number between the two groups during the intervention phase. These results imply the potential of probiotic yogurt for eliminating ETBF in the microbiota, but its clinical significance needs to be evaluated in the future. This is the first report of a possible effect of probiotic intake on ETBF in the microbiota.

Distribution of different species of the Bacteroides fragilis group in individuals with Japanese cedar pollinosis.

We investigated associations of species of the Bacteroides fragilis group with Japanese cedar pollinosis (JCPsis). Cell numbers of Bacteroides fragilis and Bacteroides intestinalis were significantly higher in JCPsis subjects than in non-JCPsis subjects before the pollen season. They correlated positively with both symptom scores and JCPsis-specific immunoglobulin E levels.

Influence of Bifidobacterium longum BB536 intake on faecal microbiota in individuals with Japanese cedar pollinosis during the pollen season.

It has been reported that intake of yogurt or powder supplemented with the Bifidobacterium longum BB536 probiotic strain alleviated subjective symptoms and affected blood markers of allergy in individuals with Japanese cedar pollinosis (JCPsis) during the pollen seasons of 2004 and 2005, based on randomized, double-blind, placebo-controlled trials. Furthermore, the 2004 study found that intestinal bacteria such as the Bacteroides fragilis group significantly fluctuated during the pollen season in JCPsis individuals and intake of BB536 yogurt tended to suppress these fluctuations. The present study investigated faecal microbiota to examine whether any changes occurred during the pollen season and whether any influence was exerted by intake of BB536 powder in the 2005 pollen season, which happened to be a heavy season, to confirm the 2004 findings and to evaluate the relationship of microbiota with symptom development. In a randomized, double-blind, placebo-controlled trial, 44 JCPsis subjects received BB536 or a placebo for 13 weeks during the pollen season. Another 14 Japanese cedar pollen (JCP)-specific IgE negative healthy subjects received placebo for the same period. Faecal samples were collected before (week 0), during (weeks 4, 8 and 13) and after (week 17) intervention, and out of JCP season (week 28). Faecal microbiota were analysed using terminal-RFLP (T-RFLP) and real-time PCR methods. Principal component analysis based on T-RFLP indicated distinct patterns of microbiota between healthy subjects and JCPsis subjects in the placebo group, but an intermediate pattern in the BB536 group at week 13, the last stage of the pollen season. The coordinate of principal component 1 at week 13 correlated with composite scores of JCPsis symptoms recorded during the pollen season. Faecalibacterium prausnitzii and the Bacteroides fragilis group were identified as the main contributors to microbiotal fluctuations. Real-time PCR indicated that BB536 intake suppressed increases in the Bacteroides fragilis group compared with the placebo group (P <0.05). These results suggest that faecal microbiota in JCPsis subjects, but not healthy subjects, fluctuate at the end of the pollen season and that BB536 intake plays a role in maintaining normal microbiota.