Acute Bacterial Meningitis

Acute bacterial meningitis is purulent infection of the leptomeninges, a medical emergency with high mortality and neurological sequelae. Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae type b are leading causes beyond the neonatal period; group B streptococci, Escherichia coli and Listeria dominate in neonates.

• Kenya lies in the African meningitis belt periphery with epidemic meningococcal disease risk in the dry season.
• Risk factors: age under 5 or over 60 years, HIV, asplenia, sickle cell disease, skull fracture, CSF leak, otitis media, sinusitis, pneumonia, cochlear implant, immunosuppression.

Fever, severe headache, neck stiffness, photophobia, vomiting, altered consciousness, seizures; petechial or purpuric rash in meningococcaemia.

• Infants: fever, irritability, poor feeding, bulging fontanelle, high pitched cry, seizures; classic neck stiffness may be absent.
• Signs: Kernig and Brudzinski signs, papilloedema (late), cranial nerve palsies, focal deficits.
• Differential diagnosis: viral meningitis, tuberculous meningitis, cryptococcal meningitis, cerebral malaria, encephalitis, brain abscess, subarachnoid haemorrhage, sepsis, typhoid, leptospirosis, neurosyphilis, meningism from pneumonia or pharyngitis.
• Complications: seizures, cerebral oedema and herniation, hydrocephalus, subdural effusion or empyema, deafness, cranial nerve palsy, cerebral infarction, cognitive deficits, septic shock, disseminated intravascular coagulation, death.

Do not delay antibiotics for investigations.

• Blood cultures before antibiotics; glucose, full blood count, CRP, clotting, urea and electrolytes, lactate; malaria test.
• Lumbar puncture unless contraindicated (focal neurological signs, papilloedema, Glasgow Coma Scale under 10, ongoing seizures, severe shock, coagulopathy, immunosuppression with focal signs): CT head first when in doubt. CSF: opening pressure, neutrophils over 100/mm3, protein over 1 g/L, glucose under 40 percent of blood glucose, Gram stain, culture, latex agglutination, PCR; India ink and cryptococcal antigen in HIV.
• HIV test and CD4.

Give antibiotics and dexamethasone within one hour of presentation.

• Supportive: admission to high dependency care, airway and oxygen, IV fluids with careful volume (avoid overload; correct shock with 10 to 20 mL/kg boluses), glucose control, treat seizures, head up 30 degrees, treat fever with paracetamol 1 g (15 mg/kg), droplet isolation for 24 hours for meningococcal disease.
• Pharmacological: ceftriaxone 2 g IV every 12 hours (children 100 mg/kg/day in 1 or 2 doses, maximum 4 g/day); add vancomycin 15 to 20 mg/kg IV every 8 to 12 hours (children 15 mg/kg every 6 hours) where penicillin resistant pneumococci are suspected; add ampicillin 2 g IV every 4 hours for those over 50 years, pregnant, or immunocompromised (Listeria). Neonates: ampicillin 100 mg/kg every 8 hours plus gentamicin 5 mg/kg daily (or cefotaxime 50 mg/kg every 8 hours). Dexamethasone 0.15 mg/kg (usual 10 mg) IV every 6 hours for 4 days, started before or with the first antibiotic dose (stop if not pneumococcal or Hib). Durations: meningococcus 7 days, Hib 7 to 10 days, pneumococcus 10 to 14 days, group B streptococcus 14 to 21 days, Listeria 21 days, gram negatives 21 days. Seizures: diazepam 10 mg IV (0.3 mg/kg rectal in children), then phenytoin 15 to 20 mg/kg. Contact prophylaxis for meningococcus: ciprofloxacin 500 mg single dose (adults), rifampicin 600 mg twice daily for 2 days (children 10 mg/kg), or ceftriaxone 250 mg IM single dose (125 mg for under 15 years).
• Procedures: lumbar puncture, CT head, intracranial pressure monitoring for coma, shunt for hydrocephalus, surgical drainage of empyema or abscess.
• Special groups: pregnancy, ceftriaxone with ampicillin; neonates, ampicillin with gentamicin or cefotaxime by weight; HIV, ceftriaxone plus a search for cryptococcus and tuberculosis; penicillin allergy, chloramphenicol 25 mg/kg IV every 6 hours (maximum 1 g) with vancomycin.
• Red flags: purpuric rash, shock, Glasgow Coma Scale falling, seizures, bulging fontanelle, focal deficit, pupil changes, hypoglycaemia.
• Follow-up: audiology within 4 weeks; neurodevelopmental review at 3 and 12 months in children; vaccination (conjugate pneumococcal, Hib, meningococcal) as appropriate; notify public health authorities.