Shigella Flashcards
Who discovered the first member of the Shigella genus?
Kiyoshi Shiga in 1886
What is the primary mode of transmission of Shigella?
Fecal-oral contamination
Which Shigella species produces the Shiga toxin?
Shigella dysenteriae serotype 1
What is the minimum infective dose of Shigella?
10-100 bacilli
What are the typical symptoms of Shigellosis?
Abdominal pain, tenesmus, dysentery (bloody diarrhea), vomiting
What are the four species of the genus Shigella?
S. dysenteriae, S. flexneri, S. boydii, S. sonnei
What environmental conditions can help spread Shigella?
Inadequate sanitation, overcrowding, and contamination via flies
What type of bacteria is Shigella (Gram stain)?
Gram-negative short rods
Which medium is the best selective media for Shigella species?
Xylose Lysine Deoxycholate (XLD) agar
What is the primary reservoir of Shigella?
Humans
What are the biochemical characteristics of Shigella species?
Oxidase negative, catalase positive (except S. dysenteriae serotype 1)
What temperature range is suitable for Shigella growth?
6-48°C, with an optimum of 37°C
How is Shigella differentiated from Escherichia coli?
Based on pathogenicity, failure to ferment lactose, and serology
What is the effect of Shiga toxin produced by S. dysenteriae?
Inhibits protein synthesis in susceptible mammalian cells
Which Shigella species is most often associated with outbreaks in developed countries?
Shigella sonnei
What are the virulence factors of Shigella species?
Invasiveness, intracellular survival, production of Shiga toxin
What type of stool sample should be collected for Shigella diagnosis?
Freshly passed stool or mucus flecks
What is the incubation period for Shigellosis?
12 hours to 4 days
What are the two stages of Shigellosis?
Early stage with watery diarrhea and second stage with dysentery