About
- Rarely seen. Check vaccination history
Characteristics
- Gram positive, club-shaped, non-motile rods growing at angles forming V,L,W shapes "Chinese letter shapes"
- Grows best with oxygen at 37 degrees
- Exotoxin only produced by those with the relevant phage
- Exotoxin has two components A and B as described below
Source
- Human reservoirs - respiratory tract
Virulence
- Those bacteria infected with the corynephage beta produces an A-B toxin
- The A component is an ADP ribosyl transferase that binds to eukaryotic elongation factor 2 blocking protein synthesis
- The B component directs the toxin to the oropharynx, heart and nerve cells
Pathogenicity
- Pharyngitis - grey dirty pseudomembrane is visibly composed of fibrin and dead cells and there is associated lymphadenopathy producing a "bull neck"
- Myocarditis and cardiac dysfunction - bradycardia, chest pain
- Laryngeal nerve palsy - hoarseness
Investigations
- Grows on Hoyle's media (Blood tellurite) producing black colonies reducing tellurite to tellurium. An alternative is the Tinsdales medium with added horse serum.
- There are 3 types - gravis (worst), intermedius, mitis (best) which suggest the severity of disease caused and can be separated by haemolysis and appearance
- Biochemical testing for catalase, urease, nitrate, pyranzinamidase, cystinase
- Test for toxin production using Elek test using antitoxin
- Serotyping and bacteriophage typing
Vaccination
- Prevention with vaccination with diphtheria toxoid
Sensitivities
- Penicillin or Erythromycin
Toxin
- Give antitoxin
Management
- Penicillin or Erythromycin
- Antitoxin
- Contacts given Erythromycin as prophylaxis
- Diphtheria immunisation