Vibrio cholerae O139 ('Bengal') strain was first identified in 1992. In contrast to O1 biotypes, O139 is characterised by:
- A Absence of cholera toxin (ctx) gene
- B Resistance to tetracycline
- C Production of a polysaccharide capsule, causing bacteraemia more frequently ✓
- D Non-motility on flagellar H antigen testing
Correct answer: C. Production of a polysaccharide capsule, causing bacteraemia more frequently
Explanation
V. cholerae O139 (Bengal serogroup) carries the same cholera toxin (ctx) gene as O1 El Tor but additionally produces a polysaccharide capsule, which protects it from serum killing and is associated with a higher rate of bacteraemia compared to O1 strains. It caused epidemic cholera in South and Southeast Asia in 1992–93. O1 strains are non-encapsulated. O139 is not inherently tetracycline-resistant; both O1 and O139 can acquire resistance. Both are motile.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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