A postoperative patient develops gas gangrene. Culture grows Clostridium perfringens. The alpha toxin responsible for membrane disruption is classified as a:

• A Pore-forming toxin disrupting ion gradients
• B Lecithinase (phospholipase C) that hydrolyzes phosphatidylcholine in cell membranes ✓
• C Superantigen activating T cells
• D AB5 toxin with enzymatic A subunit and pentameric binding B subunit

Explanation

C. perfringens alpha toxin is a lecithinase (phospholipase C) that specifically cleaves phosphatidylcholine and sphingomyelin in cell membranes, releasing diacylglycerol and ceramide; this disrupts erythrocytes, platelets, leukocytes, and muscle cells. Nagler reaction (opalescence on egg-yolk agar inhibited by antitoxin) tests for this lecithinase activity. Pore-forming toxins include staphylococcal alpha-toxin. Superantigens are TSST-1 and SEs. AB5 architecture describes cholera toxin and Shiga toxin.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.