4 groups (A, B, C, D) classified based on polysaccharide O antigens.
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.
Onset > 16 hours after ingestion
Nonmotile
Unencapsulated
Lac-
Fermentation of glucose does not produce gas
Cultured using selective Hektoen agar
First line: Azithromycin, ciprofloxacin
Antibiotic resistance widespread
Vaccine experimental
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