To compare the efficacy of a whole-cell vaccine prepared out of Escherichia coli O157:H7 strain and a toxoid vaccine prepared from modified gene of shiga-like toxin of Escherichia coli O157:H7, for having lost its pathogenicity, using rats as animal models. Samples such as ground beef, chicken intestine, raw milk and pasteurized milk was collected and analysed for the isolation and identification of Escherichia coli strain by standard microbiological techniques including antimicrobial resistance profiles. Conventional PCR amplification confirmed the presence of five selected virulence genes. A protein was produced out of stx1 gene variant from an isolate strain of Escherichia coli O157:H7 and used as a toxoid vaccine. Prepared vaccine was subjected to its efficacy test using rat models after obtaining proper ethical clearance. After challenging with ATCC and isolates, screening methods emphasised on studying the histopathology effects in liver and kidney on test rats as well as on control rats. Normal histology was seen in liver and kidney specimens of vaccinated and challenged rat groups as well as control un-inoculated unvaccinated rat groups with very few exceptional lesions. However, severe toxic evidences were observed in liver as well as kidneys of rat groups which were unvaccinated and challenged with pathogenic strains. Vaccine is believed to have lost its pathogenicity to a greater extent as validated by animal studies. When comparison was made between whole cell vaccine and toxoid, whole cell vaccine had greater extent of efficiency than toxoid.
Escherichia coli O157:H7, Toxoid Vaccine, Whole-cell vaccine, Haemolytic Uremic Syndrome
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