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 dysenteriaeGroup B - Shigella flexneriGroup C - Shigella boydiiGroup 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.

MacConkey AgarLACTOSE FERMENTERS: RED/PINK COLONIES

NON-LACTOSE FERMENTERS: COLOURLESS

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

Conventional-Biochemical tubes.JPG

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.