The Effect of bft2 and bft3 Toxins which have Been Extracted and Refined from Clinical Isolates of Enterotoxigenic Bacteroides fragilis on Mice

Abstract

This study involves isolating Enterotoxigenic Bacteroides fragilis from 94 stool samples collected from multiple hospitals in Baghdad city from March 2020 to April 2021. Stool samples were streaked onto BBE media under anaerobic conditions for 48 hours. Bacteroides fragilis was identified by analyzing its morphological characteristics on BBE media, which included the presence of gray convex tiny rounded colonies surrounded by a black zone. A molecular method was also employed, specifically targeting genes such as 16S rRNA, bft gene, bft-1, bft-2, and bft-3. A total of 34 isolates of B.fragilis tested positive for the 16S rRNA gene. Among these, 5 isolates of B.fragilis were positive for the bft gene, indicating their classification as Enterotoxigenic B.fragilis (ETBF). Furthermore, 3 isolates of ETBF were found to be positive for both bft-2 and bft-3 genes, whereas 2 isolates of ETBF were negative for all three genes (bft-1, bft-2, and bft-3). Two isolates of Enterotoxigenic Bacteroides fragilis (ETBF), which tested positive for the bft-2 and bft-3 genes, were purified using the Van Tassel technique. A total of 40 male mice were divided into four groups, with 10 mice in each group. The first group served as the control, while the second group received daily administration of 2% dextran sulfate sodium for 30 days via a stomach tube, serving as the positive control. The third group of mice also received administration via a stomach tube. After being treated with 2%DSS for 10 days, the mice were then given 20 μg of bft2 toxin through a stomach tube for 30 days. In the fourth group, the mice were also supplied through a stomach tube. The mice were treated with a 2% dextran sulfate sodium (DSS) solution for 10 days. After this period, the animals were given 20 μg of bft3 toxin through a stomach tube for 30 days. After the trial, all groups of mice were euthanized by ethical guidelines. Based on the histological abnormalities observed, it can be concluded that the combination of DSS and bft2 toxin had the most significant impact on the liver, spleen, and intestine of mice in the third group.