Corynebacterium diphtheriae
One-Sentence Definition
Corynebacterium diphtheriae is a Gram-positive rod whose toxigenic strains produce diphtheria toxin (via lysogenic phage), causing pseudomembranous pharyngitis and systemic toxicity — prevented by toxoid vaccination.
Taxonomy & Morphology
- Club-shaped Gram-positive bacillus; metachromatic granules
- Non-spore-forming; tellurite selective media (historical ID)
Virulence Highlights
- Diphtheria toxin — ADP-ribosylates EF-2 → protein synthesis arrest
- Toxin gene carried by β-phage (Transduction)
- Non-toxigenic strains cause milder colonization/infection
Clinical Syndromes
- Respiratory diphtheria — pseudomembrane, airway obstruction
- Cutaneous diphtheria (tropical/travel)
- Systemic toxin: myocarditis, neuropathy
Diagnosis
- Culture from throat/lesion; toxin PCR/Elek test for toxigenicity
- Do not delay antitoxin on culture if clinical suspicion high
Treatment / Prevention
- Diphtheria antitoxin + antibiotics (penicillin/macrolide)
- DTaP/Tdap toxoid vaccine (Vaccination)
- Close contact monitoring and prophylaxis per public health
Related Notes
- Bordetella pertussis (other vaccine-preventable toxin disease) · HEENT Infections
- MOCs: MOC - Bacteriology · MOC - Public Health & Epidemiology
Active Recall
- What converts a non-toxigenic strain to toxigenic?
- Toxin molecular target?
- Why give antitoxin before culture returns?