A 3-year-old presented with fever, meningeal signs, and CSF; Gram stain shows gram-negative diplococci. The most likely etiologic agent is?

A 3-year-old presented with fever, meningeal signs, and CSF; Gram stain shows gram-negative diplococci. The most likely etiologic agent is?

• A. Haemophilus influenzae
• B. Neisseria meningitidis
• C. Moraxella catarrhalis
• D. Listeria monocytogenes

Answer: (B)

Grams stain showing gram-negative diplococci in CSF points to Neisseria meningitidis. This organism typically appears as Gram-negative diplococci and is a leading cause of acute meningitis in young children, including preschoolers. The diplococcal morphology in the CSF is a characteristic clue that distinguishes it from other meningitis pathogens. Haemophilus influenzae would more often appear as small gram-negative coccobacilli; Listeria monocytogenes is a gram-positive rod; Moraxella catarrhalis can look like gram-negative diplococci but is a less common meningitis cause in this age group. Thus the presentation most strongly supports Neisseria meningitidis.

Grams stain showing gram-negative diplococci in CSF points to Neisseria meningitidis. This organism typically appears as Gram-negative diplococci and is a leading cause of acute meningitis in young children, including preschoolers. The diplococcal morphology in the CSF is a characteristic clue that distinguishes it from other meningitis pathogens. Haemophilus influenzae would more often appear as small gram-negative coccobacilli; Listeria monocytogenes is a gram-positive rod; Moraxella catarrhalis can look like gram-negative diplococci but is a less common meningitis cause in this age group. Thus the presentation most strongly supports Neisseria meningitidis.