Turbid CSF After a Six-Hour Journey: Presumptive Meningococcal Meningitis
A 19-year-old hostel student is brought to a district hospital at midnight with fever 39.5°C, severe headache, vomiting, photophobia, neck stiffness and a petechial rash. Lumbar puncture yields turbid CSF in three sterile containers; the first container clots before it reaches the laboratory. The samples arrive at 07:30, six hours after collection, having been kept at room temperature. Gram stain shows numerous neutrophils and Gram-negative diplococci. CSF glucose is 1.8 mmol/L with a paired blood glucose of 6.0 mmol/L; protein is 1.9 g/L. Ceftriaxone was started at 02:00. The laboratory has chocolate agar, blood agar, MacConkey agar and a candle jar, but no PCR or latex agglutination. The district health office asks whether the patient's hostel contacts need prophylaxis.
1. What is your immediate interpretation, what critical result would you telephone, and how would you set up the culture?
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Interpretation. Turbid CSF with a neutrophil predominance, a CSF:blood glucose ratio of 1.8/6.0 = 0.30, and protein 1.9 g/L is bacterial meningitis until proven otherwise. Gram-negative diplococci in CSF are presumptive Neisseria meningitidis; other Gram-negative diplococci are possible but much less likely in this age group. Culture is still needed for confirmation and susceptibility, but treatment must not wait for it.
Telephone immediately: the clinician, the infection-control nurse and the district public health office. The critical message is: 'Gram-negative diplococci seen on CSF Gram stain; presumptive meningococcal meningitis.' Document the time, recipient and advice.
Culture set-up: plate on chocolate agar and blood agar; incubate at 35–37°C in 5% CO2 using a candle jar. Do not rely on MacConkey agar, on which Neisseria does not grow. Set up a blood culture and save CSF for PCR or latex agglutination if it becomes available. Reject the clotted container for cell counting and use an unclotted aliquot; if all aliquots had clotted, request a repeat lumbar puncture only if it is safe and clinically necessary.
2. How does the six-hour delay at room temperature affect the CSF results, and what should the final report say?
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Delay at room temperature causes leucocyte lysis, so the white-cell count may be falsely low; continued glycolysis lowers glucose; lactate rises; protein is relatively stable. The clotted specimen is unsuitable for cell counting because the clot traps cells unevenly, so a count on it would be falsely low and non-representative. The Gram stain remains valid and is the most useful urgent test.
The final report should state the receipt time and specimen condition, note that the clotted aliquot was unsuitable for cell count, give the results from the unclotted aliquot, and report the Gram-stain finding as a presumptive diagnosis with culture pending. Do not present the glucose or cell count as if the sample had been processed immediately. If the only available aliquot had clotted, the correct report would be 'sample unsuitable for cell count; repeat required', while still telephoning the Gram-stain result.
3. What public health actions are indicated for the patient's hostel contacts?
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Meningococcal disease is notifiable. Public health should identify close contacts: household members, dormitory roommates, and anyone with direct exposure to oral secretions (kissing, sharing toothbrushes or cups). Offer chemoprophylaxis within 24 hours of diagnosis: rifampicin 600 mg twice daily for 2 days, ciprofloxacin 500 mg as a single dose (avoid in pregnancy), or ceftriaxone 250 mg IM as a single dose. Casual classroom contacts do not usually need prophylaxis. Provide vaccination if an outbreak is confirmed or the strain is vaccine-preventable, and give advice on early symptoms. The laboratory should save the isolate for typing and report it to the national surveillance system.