The El Tor biotype of Vibrio cholerae O1 causing pandemic cholera differs from the Classical biotype in that El Tor:
- A Produces a more potent cholera toxin and causes more severe clinical disease
- B Is Voges-Proskauer positive, haemolyses sheep erythrocytes, and is resistant to polymyxin B ✓
- C Has replaced Classical biotype in all current outbreaks and does not produce cholera toxin
- D Is serogrouped as O139 Bengal, requiring additional vaccine formulation
Explanation
El Tor biotype (responsible for 7th pandemic) differs from Classical biotype in several phenotypic characteristics: El Tor is Voges-Proskauer (VP) positive (acetoin production), haemolyses sheep and goat erythrocytes (El Tor haemolysin), is resistant to polymyxin B (50 µg), and agglutinates chicken erythrocytes (Greig test). Classical biotype is VP negative, non-haemolytic, and polymyxin B-sensitive. Both biotypes belong to O1 serogroup (Ogawa and Inaba subtypes) and produce identical cholera toxin; both cause indistinguishable clinical disease. O139 Bengal is a different serogroup causing epidemics in Asia.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.