Shigella spp Isolation and Serotyping

Shigella spp Shigella is a group of bacteria that has four different species that cause gastrointestinal illness. Group A - Shigella dysenteriae Group B - Shigella flexneri Group C - Shigella boydii Group D - Shigella sonnei

Shigella spp Isolation Shigella organisms may be very difficult to distinguish biochemically from Escherichia coli. Shigella species are Gram-negative, facultatively anaerobic, nonsporulating, nonmotile rods in the family Enterobacteriaceae. They do not decarboxylate lysine or ferment lactose within 2 days. NON-LACTOSE FERMENTERS: COLOURLESS COLONIES MacConkey Agar LACTOSE FERMENTERS: RED/PINK COLONIES

Identification bacterial pathogens in stool by biochemical testing Non-lactose fermenting, morphologically different, and well-isolated Colony from SS and/ or Mac. 1. Inoculate the Kliger’s Iron Agar (KIA) agar tube by touching the top of a colony using sterilized inculcation needle and stabbing to the bottom of the KIA. After stabbing, immediately streak the slanted surface of the agar. 2. Inoculate the Motility-Indole-Ornithine (MIO) tube by stabbing, in a single up-and-down needle. 3. Inoculate the Lysine-Iron agar (LIA) by stabbing the butt to the bottom once and streaking the slant. 4. Inoculate the urea broth tube by placing the needle in the tube and shaking the needle. 5. Incubate all tubes overnight at 35-37 Co   Conventional biochemical screening sets

Serogroups and Serotypes Each serologic group contains specific or major Somatic Antigen (O Ag) Characteristic of this group Each serologic group is subdivided on the basis of antigenic structure into Serotypes  Serotypes is further subdivided into subserotypes on the basis of antigenic structure   Serogroup Serotypes Subserotypes

Serogroups and Serotypes are determined by visual inspection of slide agglutination assays, with commercial antisera used as described by the manufacture.