Klebsiella pneumoniae is frequently mucoid on culture due to the presence of which feature?

• A. Flagella
• B. Pili
• C. Capsule
• D. Endospores

Answer: (C)

Klebsiella pneumoniae often looks mucoid on culture because it has a very large polysaccharide capsule that surrounds each cell, creating a slimy, protective layer that is released into the surrounding medium. This capsule gives colonies their distinctive shiny, mucoid appearance. The capsule is also a major virulence factor, helping the organism resist phagocytosis and persist in the host. Flagella would mainly confer movement, not a mucoid colony; pili aid in attachment but don’t cause the slimy look; endospores are not produced by Klebsiella (spore formation is typical of Bacillus and Clostridium). So the capsule best explains the mucoid appearance.