Streptococcus pneumoniae is typically identified as what form on Gram stain and culture?

• A. Gram-positive cocci in clusters
• B. Gram-positive lancet-shaped diplococci
• C. Gram-negative diplococci
• D. Gram-positive bacilli

Answer: (B)

Streptococcus pneumoniae is identified by its Gram stain and colony morphology as Gram-positive lancet-shaped diplococci.

On Gram stain, it appears as cocci in pairs with a slightly elongated, lancet-like shape, rather than in clusters. This paired, lancet appearance helps distinguish it from organisms that appear as Gram-positive cocci in clusters (such as Staphylococcus species) or Gram-positive bacilli (rods like Bacillus or Listeria), and from Gram-negative diplococci (like Neisseria).

In culture, it forms small, alpha-hemolytic colonies on blood agar and is optochin sensitive and bile soluble, features that further support its identification beyond the smear appearance.