Shigella

Characteristics/Epidemiology

4 groups (A, B, C, D) classified based on polysaccharide O antigens.

 

Pathogenesis/Transmission

Transmitted by food or faecal-oral route

Low infectious dose

Shigellae invades colonic mucosal cell by endocytosis

   -> Escapes from endocytosis

   -> Multiply inside the cell and protected from macrophages

   -> Invades neighbouring cells

   -> Cells die -> mucosal abscess

   -> Diarrhoea with blood and mucus, and abdo cramp.

Exotoxin (Shiga toxin) contributes to the changes.

 

Clinical significance

Shigellosis (Bacillary dysentry)

• Diarrhoea with blood and mucus
• Severe abdominal cramping

Onset > 16 hours after ingestion

Laboratory identification

Nonmotile

Unencapsulated

Lac-

Fermentation of glucose does not produce gas

Cultured using selective Hektoen agar

Treatment

First line: Azithromycin, ciprofloxacin

Antibiotic resistance widespread

Prevention/immunity

Vaccine experimental

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Things to revise/add later:

Bibliography:

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