Updated: 6/1/2018

Diphtheria

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Snapshot
  • A 23-year-old man presents to a travel clinic in preparation for his trip to Yemen. He reports that his last Tdap vaccine was at age 11 and he has not received any vaccinations since then. Noting especially that diphtheria outbreaks have been documented in Yemen, his physician recommends the Td booster, which is supposed to be given at 10-year intervals.
Introduction
  • Classification
    • Corynebacterium diphtheriae
      • aerobic gram + rod
      • produces diphtheria toxin
    • transmission
      • respiratory droplets
  • Epidemiology 
    • demographics
      • rare in the US
      • more common in developing countries
  • Pathogenesis 
    • diphtheria exotoxin inactivates elongation factor (EF-2) via ADP-ribosylation 
      • inhibits protein synthesis, causing necrosis in respiratory, cardiac and central nervous system tissue
      • affects mucous membranes, especially the respiratory tract
    • exotoxin is encoded by β-prophage
  • Associated conditions
    • diphtheria
    • cutaneous diphtheria
      • ulcerative lesions or cellulitis can occur independently of respiratory diphtheria
  • Prevention
    • DTap vaccine
      • vaccine against diphtheria, tetanus, and pertussis
      • 5 doses before school-age, completed by 4-6 years of age
    • Tdap vaccine
      • booster vaccine at 11-12 years of age
      • should also be given to pregnant mothers and those around them
    • Td vaccine
      • tetanus and diphtheria toxoid vaccine at 10-year intervals
  • Prognosis
    • symptoms are insidious
    • mortality is higher in young children, but generally good with prompt treatment
Presentation
  • Symptoms
    • fever
    • sore throat
    • malaise
    • may have a croup-like cough
  • Physical exam 
    • pseudomembranous pharyngitis
      • gray or bluish white membrane seen on soft palate, tonsils, or back of the throat
      • bleeds easily if irritated
      • develops 2-3 days after symptoms
    • severe cervical lymphadenopathy
      • “bull neck”
    • myocarditis 
    • arrhythmias
Studies
  • Bacterial culture
    • gram + rods with blue and red granules (metachromically) seen on culture 
      • cysteine-tellurite agar (appears as black colonies)
      • Löffler medium
    • positive Elek test for diphtheria toxin
  • Making the diagnosis
    • most cases are clinically diagnosed and confirmed with a culture
Differential
  • Streptococcal pharyngitis
    • distinguishing factor
      • no pseudomembrane on mucous membranes
Treatment
  • Medical
    • diphtheria antitoxin
      • indication
        • all patients
    • antibiotics
      • indications
        • all patients
      • drugs
        • erythromycin
        • penicillin G
Complications
  • Airway compromise from soft tissue swelling
  • Heart failure from myocarditis
  • Secondary bacterial infection (i.e., pneumonia)
 

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