El Tor biotype of Vibrio cholerae O1 differs from the classical biotype primarily because El Tor:

• A Produces more severe clinical disease with higher case fatality ratio
• B Is Voges-Proskauer positive and haemagglutinates chicken RBCs ✓
• C Is susceptible to Group IV (Mukerjee) phage but resistant to Group V phage
• D Does not produce cholera toxin and hence causes milder disease

Explanation

El Tor biotype is distinguished from classical biotype by: being Voges-Proskauer (VP) positive, haemagglutinating chicken red blood cells, producing haemolysin (Greig test positive), and being resistant to polymyxin B (50 IU). El Tor is actually more environmentally persistent and causes milder disease individually but more carrier states. Both biotypes produce cholera toxin. El Tor is susceptible to Group V phage and resistant to Group IV (Mukerjee) phage — the reverse of option C.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.