A patient returns from Bangladesh with profuse rice-water diarrhea and rapid dehydration. Stool dark-field microscopy shows comma-shaped organisms with darting motility. The El Tor biotype differs from the classical biotype by:
- A Inability to produce cholera toxin
- B Hemagglutination of sheep RBCs, resistance to polymyxin B, VP test positive, and production of a different haemolysin ✓
- C Non-pathogenic and does not cause pandemics
- D Presence of O139 antigen only
Correct answer: B. Hemagglutination of sheep RBCs, resistance to polymyxin B, VP test positive, and production of a different haemolysin
Explanation
El Tor biotype is distinguished from the classical biotype by: agglutination of chicken/sheep erythrocytes (Greig test), resistance to polymyxin B (50U disk), Voges-Proskauer (VP) reaction positive, and production of El Tor haemolysin (haemolysis of sheep RBCs); El Tor is responsible for the 7th pandemic. Both biotypes produce cholera toxin and belong to O1 serogroup. O139 is a separate non-O1 serogroup with capsule, distinct from El Tor.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.