(II) Gram Negative Rods - (6) Shigella spp.

Question 1

Name 3 ways you can distinguish Shigella from Salmonella

Answer 1

Shigella Salmonella
Green on Hektoen Black on Hektoen
Immotile Motile
Acid stable Acid labile

Question 2

Describe how Shigella infects cells

Answer 2

(1) Induces phagocytosis by M-cells
(2) Uses actin filaments to escape

(Once escaped, it’s phagocytosed by MΦs, and then induces apoptosis and subsequent Inflammation.)

Question 3

What type of diarrhea does Shigella cause?

Answer 3

(1) Inflammatory
(2) ⇒ Bloody

Question 4

What population gets HUS from Shigella?

Answer 4

Children <10 years old

(Due to Shigella DYSENTERIAE. Also associated with Reitter’s syndrome.)

Question 5

MOA: Shiga toxin

Answer 5

Inhibits 60s ribosome

Question 6

Name 3 enteric bacteria with Type III secretion systems

Answer 6

(1) Shigella
(2) Salmonella
(3) Y. enterocolitica

Question 7

Clinical presentation of Shigella:

(Depends on which strand)
1. Sh. dysenteriae: […]
2. Sh. sonnei: […]

Answer 7

Clinical presentation of Shigella:

(Depends on which strand)
1. Sh. dysenteriae: Dysentry (frequent passage of blood-stained mucopurulent stools, may be complicated by Hemolytic-uremic syndrome from Shiga toxin)
2. Sh. sonnei: common cause of mild diarrhoeal disease (outbreaks in institutions)

Question 8

Shigella is one of the leading bacterial causes of […] worldwide, causing an estimated 80–165 million cases
It is closely related to E.coli.

Transmission:
[…]

Answer 8

Shigella is one of the leading bacterial causes of diarrhea worldwide, causing an estimated 80–165 million cases
It is closely related to E.coli.

Transmission:
Faecal-oral, flies (most infections are transmitted from person to person. Very low dose is required for infection)