Experimental study on the effect of bft toxin isolated and purified from clinical isolates of Enterotoxigenic Bacteroides fragilis on the liver, spleen and intestine of mice

This study includes three parts: isolation of Enterotoxigenic Bacteroid fragilis from 94 stool samples collected from different hospitals in Baghdad city from the beginning of March/2020 to the end of April/2021. Stool samples were streaked on BBE media in an anaerobic condition for 24-48h. Identification of Fragilis was done based on morphological characteristics on BBE media: gray convex small rounded colonies surround black zone colonies and molecular method using specific genes 16S rRNA and bft gene. Results showed 34 Fragilis isolates were positive for the 16S rRNA gene and 5 Fragilis positive for the bft gene were classified as Enterotoxigenic Fragilis (ETBF). ETBF isolate which was positive for the bft gene and 16S rRNA was purified by using the Van Tassel method. 30 male mice were divided into three groups with 10 mice for each group the first group as control, the second group is positive control mice administered daily2% dextran sulfate sodium for 30 days, the third group mice administered by stomach tube 2%DSS for 10 days after 10 days mice administered with 20 µg of bft toxin by stomach tube for 30 days. At the end of the experiment, all groups of mice were killed by euthanized ethics. Tissue samples (liver, intestine, and spleen) from mice were removed. The organs were fixed in 10% neutral buffered formalin for histological techniques. Histopathological changes in the third group, in the liver section of a mouse inoculated with DSS+bft toxin, showed: necrotic hepatocytes and dilated sinusoids with hemorrhage. Histopathological changes in the intestine section of a mouse inoculated with DSS+bft toxin showed: sloughing and degenerated villi and shorten villi. Histopathological changes in the spleen section of a mouse inoculated with DSS+bft toxin showed: amyloid infiltration and all lymphoid follicles depleted with necrotic lymphocytes