Shigella dysenteriae type 1 is uniquely more virulent among Shigella species primarily because it:
- A Has a larger invasion plasmid encoding more IpaB/IpaC invasion proteins
- B Produces an endotoxin with more potent lipid A structure than other Shigella
- C Produces Shiga toxin (Stx1), identical to that of STEC, in addition to the standard invasive mechanism shared by all Shigella ✓
- D Uniquely expresses a heat-stable enterotoxin (ShET1) causing profuse watery diarrhea before dysentery
Correct answer: C. Produces Shiga toxin (Stx1), identical to that of STEC, in addition to the standard invasive mechanism shared by all Shigella
Explanation
All four Shigella species (S. dysenteriae, S. flexneri, S. boydii, S. sonnei) share the 220 kb virulence plasmid encoding the type III secretion system (Mxi-Spa) and IpaB/C/D invasion proteins for intracellular pathogenesis. However, S. dysenteriae type 1 additionally produces Shiga toxin (AB5, identical to Stx1 of STEC) encoded on a chromosomal bacteriophage. Stx contributes to the severe bloody diarrhea and risk of HUS that makes epidemic S. dysenteriae 1 dysentery more deadly than other species.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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