The bacterial genus Bacteroides inhabits the human gastrointestinal tract in greater numbers than E. coli. Feces can contain 109–1010 Bacteroides cells per gram compared with 106–108 E. coli cells per gram. Enterotoxigenic Bacteroides fragilis (ETBF), described in 1984, can cause lamb diarrheal disease, and in 1987, was associated with human diarrheal disease. ETBF is consistently identified in association with acute diarrheal illnesses in young children (age, 1–5 years) in both developed and low-resource countries. Experimental infection in rabbits and gnotobiotic piglets suggests that ETBF induces colonic inflammation. Because of the increasing threat and overall spread of antibiotic resistance, phage therapy is recognized as an antibiotic alternative. Phage therapy has been widely used in the former Soviet and Eastern European countries especially for treatment and prophylaxis of diarrheal diseases.
The aim of our study is to isolate B. fragilis from clinical samples and new bacteriophages against ETBF. The therapeutic and prophylactic potential of these phages against ETBF will be. Thirty strains of B. fragilis from patients in Belgium and Georgia were isolated from faces and other clinical materials. In vitro tests on colonic epithelial tissue culture HCT116, was used to detect enteropathogenic effect. One ETBF strains was identified from 30 isolates. Two phages were isolated from sewage water samples using B. fragilis strains as hosts. TEM studies placed these phages in the Siphoviridae family, possessing structures similar to well-known B. fragilis phages HSP40 and RYC2056 (commonly used as markers for water pollution). The collected clinical strains were screened for susceptibility to these newly isolated phages. The initial activity of both phages was about 20%, however the host ranges appeared to be different.
Studies are still ongoing to isolate and select ETBF strains, genetically analyse newly isolated bacteriophages and evaluate their therapeutic potential using colon tissue culture and/or animal models.