A 19-year-old patient presents with sudden high fever, severe headache, neck stiffness, nausea and confusion. There is a petechial rash on the lower limbs. A CSF sample was obtained and cultured. Gram stain shows Gram-negative cocci in kidney bean shape; Thayer-Martin yields smooth gray translucent colonies after 3 days. Which organism do you suspect?

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Multiple Choice

A 19-year-old patient presents with sudden high fever, severe headache, neck stiffness, nausea and confusion. There is a petechial rash on the lower limbs. A CSF sample was obtained and cultured. Gram stain shows Gram-negative cocci in kidney bean shape; Thayer-Martin yields smooth gray translucent colonies after 3 days. Which organism do you suspect?

This scenario points to meningococcal meningitis. The key clue is the combination of acute meningitis symptoms in a young adult plus a petechial rash, which is classic for Neisseria meningitidis in the bloodstream and CSF. The Gram stain showing Gram-negative cocci in pairs with a kidney-bean appearance is characteristic of Neisseria species. On a selective medium like Thayer-Martin, Neisseria meningitidis forms smooth, gray, translucent colonies after a few days, which helps confirm the organism. The other organisms don’t fit as neatly: Streptococcus pneumoniae would be Gram-positive diplococci, not Gram-negative cocci and not typically grown on Thayer-Martin; Listeria monocytogenes is Gram-positive rod and presents differently, often in other at-risk groups; Neisseria gonorrhoeae is also a Neisseria, but meningitis in this clinical context is far more typical for meningococcal disease rather than gonococcal infection.

This scenario points to meningococcal meningitis. The key clue is the combination of acute meningitis symptoms in a young adult plus a petechial rash, which is classic for Neisseria meningitidis in the bloodstream and CSF. The Gram stain showing Gram-negative cocci in pairs with a kidney-bean appearance is characteristic of Neisseria species. On a selective medium like Thayer-Martin, Neisseria meningitidis forms smooth, gray, translucent colonies after a few days, which helps confirm the organism.

The other organisms don’t fit as neatly: Streptococcus pneumoniae would be Gram-positive diplococci, not Gram-negative cocci and not typically grown on Thayer-Martin; Listeria monocytogenes is Gram-positive rod and presents differently, often in other at-risk groups; Neisseria gonorrhoeae is also a Neisseria, but meningitis in this clinical context is far more typical for meningococcal disease rather than gonococcal infection.

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