Bacteriology study of shigella species, and the effect some ecological and chemical factors.

Abstract

Shigella organisms are gram-negative rods that belongs to the family Enterobacteriace. This genus consists of four species, S. dysenteriae, S. flexneri, S. boydii and S. sonnei. These are often referred to as subgroups A, B, C and D respectively. genus was divided into four groups (designated species), on the basis of their capacity to ferment sugars and on their O-antigen serotypes. These groups are: Group A: S. dysenteriae comprised 15 serotypes. Group B: S. flexneri comprised 6 serotypes. Group C: S. boydii comprised 18 serotypes. Group D: S. sonnei comprised a single serotype. The four species can be differentiated from each other by the fermentation of sugars, sugar alcohols, production of indole, and the synthesis of ornithine decarboxylase or arginine dehydrolase. Shigella can enter into the host colonic cell, the vacuole that forms from the fusion of the cell membrane around the phagocytized Shigella and multiplication. Intra- and intercellular spread of the bacterium. The death of the host cell and ulceration of the mucosa. Resultant inflammatory response. Diarrheal are the leading worldwide cause of death among children. According to World Health Organization estimates that 5 million deaths occur annually from diarrheal diseases, and Shigella are responsible for 10% of these mortalities. The Shiga have three types of toxic activities, Neurotoxic activity; Enterotoxic and Cytotoxic activity. Shiga toxin clearly causes fluid secretion when placed in the small bowel lumen of rabbits and results in inflammatory enteritis in this model. Dysentery involves bloody diarrhea, but the passage of bloody mucoid stools is accompanied by severe abdominal and rectal pain, cramps and fever. While abdominal pain and diarrhea are experienced by nearly all patients with shigellosis, fever occurs in about one-third and gross blood occurs in about 40% of cases.