Haemophilus Influenzae Type B Infections

Key Features

Essentials of Diagnosis

• Purulent meningitis in children younger than age 4 years with direct smears of CSF showing gram-negative pleomorphic rods

• Acute epiglottitis: high fever, drooling, dysphagia, aphonia, and stridor

• Septic arthritis: fever, local redness, swelling, heat, and pain with active or passive motion of the involved joint in a child 4 months to 4 years of age

• Cellulitis: sudden onset of fever and distinctive cellulitis in an infant, often involving the cheek or periorbital area

• In all cases, a positive culture from the blood, CSF, or aspirated pus confirms the diagnosis

General Considerations

• H influenzae type b (Hib) has become uncommon because of widespread immunization in early infancy

• The 99% reduction in incidence seen in many parts of the United States is due to high rates of vaccine coverage and reduced nasopharyngeal carriage after vaccination

• Hib may cause meningitis, bacteremia, epiglottitis (supraglottic croup), septic arthritis, periorbital and facial cellulitis, pneumonia, and pericarditis

• Non–type b encapsulated strains may cause meningitis, bacteremia and other disease similar to Hib

Clinical Findings

• Meningitis

  • Fever

  • Irritability

  • Lethargy

  • Poor feeding with or without vomiting

  • High-pitched cry

• Acute epiglottitis

  • Evidence of dysphagia, characterized by a refusal to eat or swallow saliva and by drooling

  • High fever

  • Stridor is a late sign

• Septic arthritis

  • Child is febrile and refuses to move the involved joint and limb because of pain

  • Examination reveals swelling, warmth, redness, tenderness on palpation, and severe pain on attempted movement of the joint

• Cellulitis

  • Uncommon as a result of immunization

  • Cheek or periorbital (preseptal) area is often involved

Diagnosis

Laboratory Findings

• The WBC count in Hib infections may be high or normal with a shift to the left

• A positive culture of blood, CSF, aspirated pus or fluid from the involved site proves the diagnosis

• In untreated meningitis, CSF smear may show the characteristic pleomorphic gram-negative rods

Imaging

• A lateral radiographic view of the neck may suggest the diagnosis in suspected acute epiglottitis, but misinter pretation is common

• Intubation should not be delayed to obtain radiographs

Treatment

• All patients with bacteremic or potentially bacteremic H influenzae diseases require hospitalization for treatment

• Drugs of choice in hospitalized patients are a third-generation cephalosporin (cefotaxime or ceftriaxone) until the sensitivity of the organism is known

• Meropenem is an alternative choice

• Ampicillin is adequate for culture-proved susceptible strains

• Persons with invasive Hib disease should be in droplet isolation for 24 hours after initiation of parenteral antibiotic therapy

• Empiric intravenous therapy recommended for meningitis (until organism identified) is vancomycin in combination with either cefotaxime or ceftriaxone

• Duration of therapy is 10 days for uncomplicated meningitis; longer treatment is reserved for children who respond slowly or have complications

• Dexamethasone given immediately after diagnosis and continued for 4 days ...