Strongyloides stercoralis is unique among intestinal nematodes in its ability to cause hyperinfection syndrome in immunocompromised hosts. What is the key mechanism enabling this autoinfection?

• A Filariform (L3) larvae develop from rhabditiform larvae within the intestine and re-penetrate the gut mucosa ✓
• B Eggs are directly infectious when passed in feces
• C Free-living adult worms in soil re-infect through contaminated water
• D Microfilariae circulate in blood and invade the intestinal wall

Explanation

In Strongyloides stercoralis, rhabditiform (L1/L2) larvae normally pass in stool, but in autoinfection the rhabditiform larvae transform into infective filariform (L3) larvae within the intestinal lumen or on perianal skin, penetrate the mucosa or skin, and complete the life cycle without leaving the host. In immunocompromised patients this leads to hyperinfection syndrome and disseminated strongyloidiasis where larvae carry gut bacteria into systemic circulation causing gram-negative bacteremia. No other gut nematode has this capacity.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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