El Tor biotype of Vibrio cholerae, which caused the 7th pandemic, differs from classical biotype in which of the following characteristics?
- A El Tor is more sensitive to polymyxin B than the classical biotype
- B El Tor has a shorter incubation period and causes more severe dehydration
- C El Tor produces hemolysis on sheep blood agar while classical does not ✓
- D El Tor is Voges-Proskauer negative while classical is VP positive
Correct answer: C. El Tor produces hemolysis on sheep blood agar while classical does not
Explanation
Distinguishing features of El Tor biotype from classical V. cholerae O1: (1) El Tor produces hemolysis on sheep blood agar (Greig's test positive), (2) El Tor is Voges-Proskauer (VP) positive while classical is VP negative, (3) El Tor is resistant to polymyxin B (50 U), (4) El Tor agglutinates chicken RBCs. El Tor actually causes milder disease with a higher ratio of asymptomatic-to-clinical cases compared to the classical biotype.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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