Haemophilus influenzae

• A 6-year-old boy is brought to the pediatric emergency department after developing difficulty with breathing. Per his mother, his symptoms began approximately 3 hours ago and have progressively worsened. She endorses that he had an upper respiratory infection 1 week prior. His temperature is 102°F (38.9°C), blood pressure is 100/65 mmHg, pulse is 105/min, and respirations are 28/min. Physical examination is notable for him appearing distressed with inspiration and leaning forward with his neck hyperextended and chin thrust forward. Laryngoscopy demonstrated an erythematous and edematous epiglottis. (Epiglottitis)

Introduction

• Classification
  • gram-negative rod
• Epidemiology
  • incidence
    • nontypeable bacteria most commonly cause otitis media
• Transmission
  • respiratory
• Microbiology
  • oxidase positive
  • facultatively anaerobic
  • nonmotile
  • polysaccharide capsule
    • there are 6 types of capsules; however, type b is commonly associated with invasive disease
    • organisms without a capsule are said to be nontypeable
  • IgA protease
• Associated conditions
  • encapsulated (type b) strains
    • meningitis
    • epiglottitis
    • septic arthritis
  • nonencapsulated strains
    • otitis media
    • pulmonary disease in patients with preexisting lung disease (e.g., chronic bronchitis and viral influenza infection)
• Prognosis
  • haemophilus influenzae type b conjugate vaccine
• provides active immunization, which is important in preventing Hib infection

Studies

• Chocolate agar 
  • requires factors V (NAD+) and X (hematin) for growth 
• Grows near S. aureus on blood agar
  • S. aureus supplies factor

Presentation