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

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.

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.