Dissection of the key intestinal microbiota in residents of Pemba Island in Tanzania and use of Bifidobacterium breve in prevention against colitis in mice

Pemba Island is located on the eastern coast of Tanzania and is one part of the Zanzibar Islands. The climate on the island is mild, and the temperature is kept between 24°C and 28°C throughout the year. Therefore, the residents on the island plant plenty bananas and feed on them. In addition, the residents of the island consume large amounts of vegetables and fruits, mainly cassava, rice and corn as their staple food, and fish as the main source of animal food. The parasitic diseases in Africa are highly prevalent, which seriously endangers the quality of life of the African people. The prevalence of soil-borne helminthiasis on Pemba Island is relatively high. The research center Public Health Laboratory Ivo de Carneri (PHL-IdC) hosts researchers from many countries on Pemba Island to carry out scientific research. The field part of the investigation reported in this thesis was conducted with the support of the PHL-IdC. At present, there are very few studies on the dietary structure of African island residents. Most of the research are carried out on the dietary structure of Western countries, such as the Mediterranean diet and the typical Western diet. In this study, a total of 32 pairs (64) of mother and child volunteers on Pemba Island with similar diets were recruited in three different villages on the Island. First, we used the Food Frequency Questionnaire (FFQ) to analyze the dietary structure and food composition of women and their children. At the same time, we used 16S rDNA high-throughput sequencing technology to study the intestinal flora of the volunteers. Heat maps were utilized to show the correlation between gut microbiota and diet structure, gut microbiota and nutrient intake. We found that Pemba women and children’s diets were characterized by high carbohydrate and high dietary fiber intake, low protein and low fat intake. Supply ratios of carbohydrate, fat and protein were out of balance; The percentage of carbohydrates supply was too high, the percentage of fat supply was too low. There was a significant positive correlation between the abundance of Faecalibacterium and the intake of Cu, and a negative correlation between Faecalibacterium and the intake of fat in the intestine of healthy Pemba women. There was a significant positive correlation between Bacteroides and Se, and a significant negative correlation between Bacteroides and Cu in the intestine of healthy Pemba children (Chapter 2). Secondly, we used the gut microbiota of healthy Spanish women and Australian children as reference to analyze the similarities and differences in the structure and function of the core intestinal microbiota of healthy women and children from Pemba Island. We found that Firmicutes and Bacteroidetes were the dominant phyla in the gut microbiota of Pemba women and children, moreover, Prevotella was the dominant genus. The structure of the gut microbiota in healthy Pemba women was significantly different from that of Spanish women, and the structure of the gut microbiota of Pemba children was also significantly different from the Australian children; PICRUST prediction analysis revealed that the metabolic pathways "Lipid metabolism" and "Nucleotide metabolism" showed significantly higher abundance in women and children from Pemba Island, compared with Spanish women and Australian children respectively (Chapter 3). Then, based on the results of the Mini-Flotac parasitological examination, we divided all volunteers of Pemba Island into four groups, healthy women group, whipworm-infected women group, healthy children group, whipworm-infected children group, and used bioinformatics technology to analyze the association between the intestinal microbiota and whipworm infection. We found that, compared with healthy women and children, the diversity of the gut microbiota of whipworm-infected women and children were higher, especially in the microbiota of the infected women, the alpha diversity and beta diversity of infected women were significantly increased. Short-chain fatty acid-producing bacteria such as Blautia and Bacteroides showed decreased level in whipworm-infected children, and short-chain fatty acid-producing bacteria such as Prevotella 2, Prevotella 9 and Ruminococcaceae UCG-005 showed decreased level in whipworm-infected women volunteers. Opportunistic pathogens such as Enterococcus showed increased level in whipworm-infected children, and Campylobacter showed elevated level in whipworm-infected women; the abundance of Bifidobacterium exerted decreased amount in the gut of healthy women and children with respect to the infected counterpart. Notably, in the healthy women’s gut, the abundance of Bifidobacterium presented a significantly reduced level (Chapter 4). Finally, we speculated that Bifidobacterium may have the potential to regulate IBD. Therefore, in the last chapter, we used Bifidobacterium breve to intervene in the mouse IBD model to explore the potential immune regulation of B. breve. We found that low concentration of B. breve could reduce the DAI index of DSS-induced mouse colitis, reduce colon shortening and slice pathological damage, and exert preventive roles. B. breve could promote the secretion of anti-inflammatory cytokines and inhibit the expression of pro-inflammatory cytokines in serum, at the same time, it could increase the number of CD4+CD25+Foxp3+ Treg cells, and inhibit the number of CD3+CD4+ IL- 17+Tcells in mesenteric lymph nodes, to reduce intestinal injury. Low-concentration B. breve intervention could also improve the composition of the gut microbiota, reduce the loss of short-chain fatty acid-producing bacteria, reduce the production of pro- inflammatory bacteria, reshape the intestinal microecology and reduce intestinal inflammation (Chapter 5).