Bacterial Infections and Aseptic Meningitis
Acute Purulent Meningitis
Progression for hours. Polymorphonuclear pleocytosis usually present in CSF.
General Considerations
Routes of meningeal infection: (a) blood (septicemia or spread from distant sites, e.g., heart, lung); (b) direct extension from local septic focus (e.g., sinusitis, brain abscess); (c) openings in skull (e.g., compound fractures, neurosurgery).
Signs of meningeal irritation: stiff neck; Kernig sign (pain in back or neck as either leg is passively flexed at hip and extended at knee); Brudzinski sign (flexion of legs at hip in response to passive neck flexion). Often absent in newborn, elderly, or comatose patients.
Symptoms and clinical course similar regardless of organism.
Most common organisms differ by age.
Adults: Streptococcus pneumoniae, then Neisseria meningitidis, then cryptogenic (organism not identified).
Children: Hemophilus influenzae in past; now very rare due to HIB vaccination.
Evaluation: acute meningeal syndrome mandates emergency lumbar puncture and emergent empiric intravenous antibiotic therapy.
Initial antibiotic therapy: third generation cephalosporin and vancomycin; add ampicillin if Listeria monocytogenes is considered. Definitive therapy dictated by organism and identified source of infection.
Mortality of acute bacterial meningitis: 3–21% (depending on organism), mostly in first 48 hours.
Meningococcal Meningitis
Epidemiology
25% of all bacterial meningitis in United States. Children and young adults predominantly affected. Spread by carriers or infected individuals. Vaccine available against some serogroups.
Symptoms and Signs
Chills and fever, headache, nausea and vomiting, back pain, stiff neck, prostration. Herpes labialis, conjunctivitis, and petechial or hemorrhagic rash common. Characteristic sharp shrill cry in children (meningeal cry). Fever (101–103° F; temperature may be normal with older age, diabetes), tachycardia, tachypnea.
Delirium, stupor, coma. Convulsive seizures frequent. Cranial nerve palsies, focal neurologic signs uncommon early in course.
Laboratory Data
Increased white blood cell (WBC) count; organism may be cultured from nasopharynx, blood, or skin lesions.
CSF: high pressure, cloudy, high WBC count (mostly neutrophils), high protein, low glucose. Gram stain: gram-negative diplococci intra- and extracellular. Culture positive in 90% of untreated cases.
Diagnosis
Diagnosis likely in patient with headache, vomiting, chills and fever, stiff neck, petechial rash. Confirmed by CSF Gram stain and culture. (Rapid bacterial antigen detection in CSF possible, but less sensitive and specific).
Treatment
Initial antibiotics for bacterial meningitis: third-generation cephalosporin (ceftriaxone, cefotaxime) and vancomycin (for cephalosporin-resistant streptococcus). Start no later than 1 to 2 hours after obtaining history and examination consistent with diagnosis.
May change antibiotics to penicillin (chloramphenicol if allergic) after Gram stain or culture confirm organism and sensitivity.
Reexamine CSF after 24 to 48 hours if no dramatic improvement.
Intravenous fluids for dehydration (common), heparin for disseminated intravascular coagulation, anticonvulsants for seizures.
Consider corticosteroids (see below). Prophylactic rifampin for people in intimate contact with patient.
Prognosis
Overall mortality rate about 10%.
Complications and Sequelae
Neurologic: convulsions, cranial nerve palsies (including deafness), focal cerebral lesions, damage to spinal cord or nerve roots, hydrocephalus.
Systemic (if other body sites infected): panophthalmitis, arthritis, purpura, pericarditis, endocarditis, myocarditis, pleurisy, orchitis, epididymitis, albuminuria or hematuria, adrenal hemorrhage, disseminated intravascular coagulation.
Hemophilus Influenzae Meningitis
Rare in United States and other countries with vaccination. More frequent in adults in these countries; infancy, early childhood elsewhere.
Pathology, symptoms, signs, and CSF and other laboratory abnormalities: as in other acute purulent meningitis.
Risk factors: acute sinusitis, otitis media, skull fracture, autumn or spring season. Associated with immunodeficiency, diabetes, and alcoholism.
Diagnosis: CSF culture or detection of capsular antigens in CSF (more rapid but less sensitive and specific).
Treatment: initially as in other acute purulent meningitides; add ampicillin to cover Listeria in neonates and others at risk (see below). Continue antibiotics for 12 to 15 days. Corticosteroids (given in first 2 to 4 days) reduce frequency of sequelae in children with H. influenzae or streptococcal meningitis. Role in adults not established.
Course and prognosis: Duration 10 to 20 days; occasionally fulminant. Mortality >90% in untreated infants, 10% with treatment. Sequelae: mental retardation, seizures, blindness, ocular palsies, deafness, hemiplegia. Suspect subdural effusion (most common with H. influenzae) in children with persistent vomiting, bulging fontanelles, convulsions, focal neurologic signs, persistent fever. Treat effusion by needle aspiration.
Pneumococcal Meningitis
Organism: Streptococcus pneumoniae.
Sources: otitis media, sinusitis, skull fracture, upper respiratory infection, lung infection.
Risk factors: alcoholism, asplenism, sickle-cell disease, age (<1 year or >50 years).
Treatment: as for H. influenzae meningitis. Eradicate primary infection, surgically if necessary. Close persistent CSF fistula by suturing dura.
Prognosis: mortality 20% to 30%. Good prognostic factors: meningitis after skull fracture or with no known infection. Poor prognostic factors: pneumonia, empyema, lung abscess, endocarditis.
Meningitis Due to Other Streptococci
Less than 5% of all meningitis. Always secondary to septic focus elsewhere.
Clinical manifestations, laboratory findings, and treatment: similar to pneumococcal meningitis.
Group B streptococcus most common cause of meningitis in neonates (see below).
Staphylococcal Meningitis
Relatively infrequent.
Sources: furuncles on face, cavernous sinus thrombosis, epidural or subdural abscess, intraventricular shunts, endocarditis.
Clinical features: as in other acute meningitis.
Treatment: initially as described above. When staphylococcal species identified, change to penicillinase-resistant penicillin; add vancomycin if resistance is likely (e.g., if nosocomial). Treat for 2 to 4 weeks. Eradicate source of infection.
Acute Meningitis Caused by Other Bacteria
Gram-Negative Bacilli
E. coli is second most common cause of meningitis in neonates (after Group B strep). Often accompanies septicemia. Clinical syndrome: irritability, lethargy, bulging fontanelle.
Also occurs in adults with immunosuppression, chronic illness, diabetes, penetrating head injury, neurosurgery.
Treatment: third-generation cephalosporin (ceftazidime if Pseudomonas aeruginosa suspected) and aminoglycoside. Mortality 40–70%.
Listeria Monocytogenes
At risk: neonates; adults with chronic disease. Diagnosis: “diphtheroids” in CSF Gram stain. May cause prominent brainstem signs (rhomboencephalitis).Related posts:
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