AKT · Infections/Key pathogens & antimicrobials

Bacterial meningitis

Organism varies with AGE and host — meningococcus, pneumococcus, Listeria

Overview

Infection of the meninges — a medical emergency. Organism by age/host: neonates → Group B strep, E. coli, Listeria; children/adults → Neisseria meningitidis (meningococcus) & Streptococcus pneumoniae (pneumococcus); elderly/immunocompromised/pregnant → add Listeria (needs amoxicillin cover). Meningococcal disease adds a non-blanching purpuric rash (meningococcaemia). Classic triad: fever, headache, neck stiffness (± photophobia, Kernig/Brudzinski). Give antibiotics IMMEDIATELY — do not delay for imaging/LP. CSF: bacterial = ↑neutrophils, ↑protein, ↓glucose, turbid.

Recognise

Fever, severe headache, neck stiffness, photophobia; reduced consciousness/seizures if severe; non-blanching rash = meningococcal
CSF: neutrophilic pleocytosis, high protein, LOW glucose (vs viral: lymphocytes, normal glucose)
Community: benzylpenicillin (GP, pre-hospital); hospital: ceftriaxone; add amoxicillin (Listeria) if >50/immunocompromised/pregnant; dexamethasone with/before antibiotics (pneumococcal)

Red flags

Non-blanching rash / signs of shock → meningococcal sepsis: antibiotics + fluids immediately, do NOT wait for LP
Reduced GCS, focal signs, papilloedema → CT before LP, but give antibiotics FIRST

Differentials & how to tell them apart

Viral (aseptic) meningitislymphocytic CSF, normal glucose, usually self-limiting (enterovirus, HSV)

Subarachnoid haemorrhagethunderclap onset; CT/xanthochromia — not infective

Encephalitisaltered mental state/seizures dominate → aciclovir for HSV (cross-ref neurology)

Investigations

Blood cultures + give antibiotics immediately; lumbar puncture (CSF microscopy/culture/PCR, protein, glucose paired with serum) unless contraindicated (↑ICP/coagulopathy/shock — then treat first); meningococcal/pneumococcal PCR; FBC/CRP/glucose.

Management

Immediate ceftriaxone (benzylpenicillin pre-hospital) + dexamethasone; add amoxicillin for Listeria cover; notify + contact prophylaxis

1Recognise meningism/sepsis and give antibiotics IMMEDIATELY (benzylpenicillin pre-hospital, ceftriaxone in hospital) with dexamethasone; take blood cultures. Do LP if safe.Gate: Do NOT delay antibiotics for LP or CT — treat on clinical suspicion. A non-blanching rash = meningococcal sepsis: antibiotics + fluids now, notify public health.
2Add amoxicillin for Listeria in the >50/immunocompromised/pregnant; arrange contact tracing + ciprofloxacin prophylaxis; the disease is statutorily notifiable on suspicion.

Benzylpenicillin (pre-hospital) / ceftriaxone (hospital) — give IMMEDIATELY — before LP/imaging; do not delay

Add amoxicillin — cover Listeria if >50, immunocompromised or pregnant

Dexamethasone — with or just before antibiotics — reduces complications in pneumococcal meningitis

Ciprofloxacin prophylaxis for contacts — close contacts of meningococcal disease; NOTIFY public health

Key points

Organism by age: neonate → GBS/E. coli/Listeria; child/adult → meningococcus & pneumococcus; >50/immunocompromised/pregnant → add Listeria (amoxicillin). Antibiotics FIRST (benzylpenicillin pre-hospital, ceftriaxone in hospital) + dexamethasone; don't wait for LP/CT. Bacterial CSF = neutrophils, high protein, LOW glucose. Notifiable.

Monitor & prognosis

GCS/neurology, repeat inflammatory markers, complications (hearing, seizures, hydrocephalus), public-health contact tracing.

Good if treated immediately; delay increases death and sequelae (deafness, neurodisability); pneumococcal has the worst outcomes.

Source: NICE NG240 (meningitis); UKHSA; cross-ref neurology (CSF table)