In suspected meningitis, which diagnostic test helps identify the causative organism?

• A. Lumbar puncture with CSF analysis
• B. MRI brain
• C. Abdominal ultrasound
• D. ECG

Answer: (A)

Identifying the causative organism in suspected meningitis hinges on obtaining cerebrospinal fluid for direct analysis. A lumbar puncture provides CSF that can be examined with Gram stain and cultured (and tested by PCR) to detect bacteria, viruses, or fungi responsible for meningitis. This direct microbiologic testing can pinpoint the pathogen and guide targeted therapy, whereas imaging like MRI, or tests such as abdominal ultrasound or ECG, do not identify the CNS organism. CSF analysis also helps distinguish bacterial from viral meningitis through cell counts, glucose, and protein, but the key factor for organism identification is the CSF microbiologic workup.