A 20-year old male patient complains of severe abdominal pain and passage of bloody diarrhea. Physical examination reveals fever of 101degF. Stool examination revealed numerous pus cells and red blood cells. The patient's symptoms are associated with an epidemic of contaminated water and food. The characteristic feature of the organism responsible for the patient's symptoms includes which of the following?

The etiologic agent is Shigella species, which is responsible for invasion of colonic mucosa and causes subsequent death and necrosis. Toxins produced by Shigella inhibit protein synthesis by mucosal epithelial cells. Affected patients are feverish and complain of lower abdominal pain along with severe bloody diarrhea. Nausea and vomiting is uncommon. Stool examination gives clues to the invasive nature of the organisms (presence of many pus cells and red blood cells). There is also an association to epidemics of contaminated food and drinks. Ref: Ray C.G., Ryan K.J. (2010). Chapter 33. Enterobacteriaceae. In C.G. Ray, K.J. Ryan (Eds), Sherris Medical Microbiology, 5e.