Partially treated bacterial meningitis with a negative culture
A 3-year-old boy is brought with 6 days of fever and 2 days of lethargy and vomiting. He was seen on day 2 and prescribed oral amoxicillin 250 mg three times daily for 5 days for presumed otitis media; he has taken it irregularly. He is now drowsy, with a temperature of 38.9°C, neck stiffness, and photophobia. There are no petechiae. A lumbar puncture is performed after a normal CT scan: opening pressure 28 cm CSF, white cells 380/microlitre (65% neutrophils), red cells 5/microlitre, protein 1.3 g/L, glucose 1.9 mmol/L with a simultaneous blood glucose of 5.4 mmol/L. Gram stain and culture are negative. CRP is 148 mg/L. He has no seizures and no focal deficit. Immunisations are up to date except he missed the 12-month booster.
1. How do you interpret the CSF findings and what is your working diagnosis?
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The CSF shows a neutrophilic pleocytosis (380 white cells/microlitre, 65% neutrophils), raised protein (1.3 g/L) and low glucose (1.9 mmol/L with a blood glucose of 5.4 mmol/L, ratio 0.35). This is a bacterial profile. The negative Gram stain and culture are explained by 5 days of oral amoxicillin, which can sterilise the CSF and reduce culture yield while the inflammatory response persists. The normal CT does not exclude meningitis; it was done to exclude raised intracranial pressure before lumbar puncture.
The working diagnosis is probable bacterial meningitis, partially treated. The main organisms in a 3-year-old are Streptococcus pneumoniae and Neisseria meningitidis; Haemophilus influenzae type b is less likely because he is immunised, although he missed the 12-month booster. I would not dismiss the diagnosis because the culture is negative. I would review the immunisation record, ask about sick contacts, and examine for petechiae, otitis media and sinusitis. Blood cultures, polymerase chain reaction on CSF for pneumococcus and meningococcus, and meningococcal polymerase chain reaction on blood may improve pathogen detection.
2. What antibiotic and adjunctive treatment would you start, and for how long?
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Start empirical intravenous ceftriaxone 100 mg/kg/day in one or two doses (maximum 4 g/day), or cefotaxime 200 mg/kg/day divided every 6 hours. Add vancomycin 15 mg/kg every 6 hours if there is concern about penicillin-resistant pneumococcus, guided by local epidemiology, and monitor levels. Give dexamethasone 0.15 mg/kg every 6 hours for 2 days, ideally before or with the first antibiotic dose; if antibiotics have already been given, it may still reduce hearing loss, particularly in pneumococcal meningitis, but the benefit is less certain.
Duration depends on the pathogen. If pneumococcus is confirmed, 10-14 days; meningococcus, 7 days; Haemophilus influenzae type b, 7-10 days; Listeria, 21 days. With a negative culture, I would treat for 10-14 days, guided by clinical response and inflammatory markers. Supportive care includes fluid and electrolyte management, monitoring for seizures and raised intracranial pressure, and avoiding hypotonic fluids. Repeat lumbar puncture is not routinely needed if the child improves, but it is indicated if there is no improvement or deterioration.
3. What public health and follow-up actions are required?
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Notify public health immediately because bacterial meningitis is notifiable. Chemoprophylaxis is indicated for household and close contacts only if the pathogen is meningococcus or Haemophilus influenzae type b. With a negative culture, the decision is uncertain; public health will advise. If meningococcal disease is suspected, give ciprofloxacin or rifampicin to household contacts. If Haemophilus influenzae type b is confirmed, give rifampicin to household contacts and review immunisation status. There is no need for prophylaxis for pneumococcus.
Follow-up: audiology testing for all children after bacterial meningitis, because sensorineural hearing loss is a common sequela, especially with pneumococcus. Arrange a developmental and neurological review, and advise parents to return if there is fever, lethargy, poor feeding, seizures or behavioural change. Check that the child's immunisations are up to date and catch up on the missed 12-month booster. Document the partially treated episode and communicate with the general practitioner. If there is any concern about immune deficiency, consider an immunological assessment, but recurrent meningitis is more suggestive than a single episode.