Meningitis and encephalitis — CSF, Listeria cover and aciclovir

CSF interpretation. Neutrophilic pleocytosis, high protein and a low CSF:serum glucose ratio is bacterial meningitis until proven otherwise. The Dutch adult cohort medians in proven bacterial meningitis were WCC 2400/mm3, protein 3.90 g/L and glucose 0.50 mmol/L — this table sits in the same neighbourhood. Measure blood glucose with the LP (NICE).^[9][2]

Antibiotics vs imaging vs LP. Bloods then antibiotics within 1 hour of arrival. LP before antibiotics only if safe and not delay-causing. Hasbun: abnormal consciousness, age 60 or over, immunocompromise, known CNS disease, and seizure within a week are associated with an abnormal CT (NPV 97 per cent when none present). NICE imaging-before-LP stops include new focal neurology (seizures or posturing), abnormal pupils, and GCS 9 or less. GCS 12 is not yet 9, but abnormal consciousness is still a Hasbun feature — antimicrobials first, then image if those stops apply, then LP. Imaging never delays the first antibiotic.^[2][6]

Empiric regimen for this 68-year-old.

• Ceftriaxone at the highest BNF/BNFC dose within 1 hour
• Dexamethasone 10 mg IV with or before the first antibiotic, then 6-hourly for 4 days (de Gans); still give if delayed less than 12 hours
• IV amoxicillin in addition, because NICE adds it when Listeria risk factors are present; Dutch Listeria cases were immunocompromised in 66 per cent and had 32 per cent mortality. Confirmed Listeria: amoxicillin or ampicillin for 21 days
• Do not routinely add aciclovir unless HSV encephalitis is strongly suspected (this CSF is neutrophilic with low glucose — bacterial until proven otherwise)^[2][5][9]

Evidence anchors. NICE NG240 for sequence, durations and Listeria add-on; de Gans 2002 for dexamethasone 10 mg; Hasbun 2001 for CT-associated features; Drost 2026 for contemporary epidemiology and Listeria mortality.^[2][5][6][9]