The initial evaluation for a patient with suspected bacterial meningitis should include at least a complete blood count, two sets of blood cultures and if available CRP and PCT. CSF evaluation is a must. When a lumbar puncture cannot be done immediately, blood cultures should be drawn and empiric antibiotics administered.

• The CSF should be sent for cell count, sugar and protein, gram stain and culture. An extra sample should be preserved for later tests that may be required. Samples should ideally be examined within 30- 60 minutes to increase positivity in CSF culture and for accurate assessment of cell counts. If the delay is expected the samples should be kept at room temperature and never refrigerated. The sensitivity of latex agglutination tests is kit dependent and variable.
• Molecular tests have enhanced sensitivity as compared to cultures and can be requested if available. Commercially available multiplex meningitis panels covering common bacterial, viral and fungal pathogens that cause community acquired meningitis (Pneumococcus, Meningococcus, H. Influenza, Group B Streptococcus, Listeria, E. coli K1, Cytomegalovirus, Enterovirus, Herpes simplex virus 1 and 2, Human herpes virus 6, Human parechovirus, Varicella zoster virus and Cryptococcus neoformans/gattii
• The empiric antibiotic regime for suspected/ probable bacterial meningitis is discussed in Table.



Etiology and empiric therapy of community acquired acute bacterial meningitis

Age	Likely pathogens	First line	Alternative
Age < 1 month	Gram negative ( Klebsiella, E coli, Pseudomonas, Acinetobacter) Staphylococcus, Enterococcus, Pneumococcus, Candida	Meropenem (Add vancomycin if risk of MRSA)	Cefotaxime and gentamicin
1month – 50 years	S. pneumoniae, Haemophilus influenzae, Meningococcus	Ceftriaxone and vancomycin	Cefotaxime and vancomycin
>50 years, alcoholism or other diseases of impaired CMI	S. pneumoniae, Meningococcus, Listeria, gram negative bacilli	Ampicillin and ceftriaxone and vancomycin	Meropenem and vancomycin

• The administration of dexamethasone 15- 20 minutes prior to giving the first dose of antibiotic has been found to be beneficial for pneumococcal meningitis in adults and Hemophilus influenza meningitis in children. The benefit of dexamethasone in childhood pneumococcal meningitis is debatable. The dose is 0.15 mg/kg every 6 hours for 48 hours -96 hours (10 mg 6 hourly in adults). A practical issue is that the turnaround time for confirmation of etiology of meningitis is at least 48 hours unless molecular tests are used. Also in most suspected meningitis, the first dose of antibiotic is given soon after drawing blood cultures/ doing the lumbar puncture even before the basic CSF reports come in. Therefore it is acceptable to at least give one dose prior to the antibiotic in suspected meningitis. Further doses can be continued depending on the CSF reports. Steroids are not recommended for meningitis in neonates.
• If an organism is identified, therapy can be modified accordingly. If the organism is cephalosporin susceptible, vancomycin can be stopped. Consider adding rifampicin if cephalosporin MIC ≥4 µg/mL, if the child’s condition worsening after 48 hours of vancomycin + ceftriaxone, if dexamethasone has been given or if repeat LP shows the presence of bacteria.
• In patients improving clinically, there is no need to repeat CSF analysis to demonstrate improvement or prior to stopping therapy. Repeat CSF should be done in cases of clinical non response at 48 hours, patients with penicillin/cephalosporin resistant strains who have received adjunctive dexamethasone, and in neonates to document sterilization of CSF. Causes of clinical non response in a case of bacterial meningitis include complications such as subdural empyema, cerebral abscess, ventriculitis etc or drug resistance.
• The duration of therapy for uncomplicated meningitis is generally 10-14 days. If a specific pathogen is identified then duration is pathogen dependent: 7 days for meningococcus and H. influenzae, 10-14 days for pneumococcus, 2-3 weeks for group B Streptococcus, 3-6 weeks for Listeria, and 3 weeks for gram negative meningitis.