Question:
The polysaccharide capsule of which of the following bacteria has NO role in its infectivity?
The polysaccharide capsule of which of the following bacteria has NO role in its infectivity?
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Three are classic capsulated invaders; one relies on toxins and adhesins.
Updated On: Jun 24, 2026
- Neisseria meningitidis
- Pneumococcus
- Bordetella pertussis
- Haemophilus influenzae
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The Correct Option is C
Solution and Explanation
Step 1: A polysaccharide capsule is a major virulence factor for many bacteria because it resists phagocytosis and complement-mediated killing.
Step 2: Neisseria meningitidis has a polysaccharide capsule that is central to its virulence and forms the basis of serogrouping and vaccines.
Step 3: Streptococcus pneumoniae (pneumococcus) has a polysaccharide capsule that is its principal virulence factor and the antigen used in pneumococcal vaccines.
Step 4: Haemophilus influenzae type b owes its invasiveness to its polyribosyl ribitol phosphate (PRP) polysaccharide capsule, the target of the Hib vaccine.
Step 5: Bordetella pertussis causes disease mainly through toxins and adhesins, such as pertussis toxin, filamentous haemagglutinin, pertactin, adenylate cyclase toxin and tracheal cytotoxin. Its pathogenicity is not based on a polysaccharide capsule.
Conclusion: The capsule has no role in the infectivity of Bordetella pertussis, so the printed key (C) is correct.
Step 2: Neisseria meningitidis has a polysaccharide capsule that is central to its virulence and forms the basis of serogrouping and vaccines.
Step 3: Streptococcus pneumoniae (pneumococcus) has a polysaccharide capsule that is its principal virulence factor and the antigen used in pneumococcal vaccines.
Step 4: Haemophilus influenzae type b owes its invasiveness to its polyribosyl ribitol phosphate (PRP) polysaccharide capsule, the target of the Hib vaccine.
Step 5: Bordetella pertussis causes disease mainly through toxins and adhesins, such as pertussis toxin, filamentous haemagglutinin, pertactin, adenylate cyclase toxin and tracheal cytotoxin. Its pathogenicity is not based on a polysaccharide capsule.
Conclusion: The capsule has no role in the infectivity of Bordetella pertussis, so the printed key (C) is correct.
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