- The four most likely pathogens of bacterial meningitis in the United States are Streptococcus pneumoniae, group B Streptococcus, Neisseria meningitidis, and Haemophilus influenzae type b, although routine vaccination is having a dramatic effect on the incidence of these pathogens causing infection.
- In cases of meningitis, initial findings can include (a) presenting signs and symptoms: fever, headache, nuchal rigidity (the classic triad), Brudzinski’s or Kernig’s sign, and altered mental status; and (b) abnormal cerebrospinal fluid (CSF) chemistries: elevated white blood cell (WBC) count (>1,000 cells/mm3 [>1 × 109/L]), elevated protein (>50 mg/dL [>500 mg/L]), and decreased glucose levels (<45 mg/dL [<2.5 mmol/L).
- Two main microbiologic tests that should be obtained include a Gram stain and culture of the CSF. Molecular testing such as polymerase chain reaction, latex coagglutination, and enzyme immunoassay (EIA) tests provide for the rapid identification of several causes of meningitis.
- Three primary goals of treatment in meningitis include (a) eradication of infection, (b) amelioration of signs and symptoms, and (c) prevention of the development of neurologic sequelae, such as seizures, deafness, coma, and death.
- When selecting antibiotics, the clinician must consider the antibiotic concentration at the site of infection, as well as the spectrum of antibacterial activity. Empirical choices should be based on age, predisposing conditions, and comorbidities. (a) Ceftriaxone or cefotaxime and vancomycin are reasonable initial choices for empirical coverage of community-acquired meningitis in adult patients. (b) Listeria monocytogenes is a common pathogen in infants and elderly; therefore, ampicillin with or without gentamicin should be added empirically to antimicrobial coverage.
- Empirical coverage with an appropriate antibiotic should be started as soon as possible when clinical suspicion of meningitis exists. If there is a delay in doing a lumbar puncture (even 30 to 60 minutes), or if the patient is to undergo neuroimaging, the first dose of an antibiotic should not be withheld. Changes in the CSF after initiation of antibiotics usually take 12 to 24 hours.
- Antibiotic dosages for the treatment of meningitis should be optimized to ensure adequate CNS penetration.
- The duration of antibiotic treatment for meningitis has not been standardized; however, the duration generally is based on the causative organism and the individual case and may range from 7 to 21 days.
- Close contacts and relatives of the index case should be assessed for appropriate prophylaxis, particularly for N. meningitidis and H. influenzae meningitis.
- Steroid treatment includes dexamethasone 0.15 mg/kg per dose to be given four times daily for 4 days in infants and children older than 2 months of age with proven or strongly suspected bacterial meningitis. Steroids should be started prior to the first dose of antibiotics.
On completion of the chapter, the reader will be able to:
Define meningitis and encephalitis.
List, in order of relative incidence, the most common age-dependent bacterial causes of meningitis, and identify the fatality rate associated with each.
Analyze laboratory values of CSF components and describe the values as normal or as indicative of a ...