A Vibrio cholerae O1 El Tor isolate is typed by the Haemagglutinin (HA) protease, sensitivity to Mukherjee's phage IV, and polymyxin B susceptibility. The isolate is sensitive to polymyxin B and sensitive to Mukherjee's phage IV. Which biotype does this represent?
- A Classical biotype ✓
- B El Tor biotype
- C O139 serogroup
- D Non-O1/Non-O139 (NAG) Vibrio
Correct answer: A. Classical biotype
Explanation
Vibrio cholerae O1 exists as two biotypes — Classical and El Tor. The Classical biotype is sensitive to polymyxin B (MIC ≤50 IU) and sensitive to Mukherjee's phage IV. The El Tor biotype is resistant to polymyxin B and resistant to Mukherjee's phage IV. Additional distinguishing features: El Tor haemolyses sheep RBCs (Greig test positive), agglutinates chicken erythrocytes (Haemagglutination positive), and gives Voges-Proskauer test positive. The 7th pandemic of cholera is caused by El Tor biotype; the Classical biotype predominated in earlier pandemics.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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