Johns Hopkins ABX Guide
Corynebacterium diphtheriae (Diphtheria)
MICROBIOLOGY
- Pleomorphic Gram-positive bacillus that is club-shaped, appears like Chinese characters on Gram stain [Fig1].
- Facultative anaerobe
- Humans are the only known C. diphtheriae hosts.
- Diphtheria is caused only by exotoxin-producing strains of C. diphtheriae.
- Three Corynebacterium strains may produce diphtheria toxin:
- C. diphtheriae (epidemic diphtheria w/ person-person spread)
- C. ulcerans
- C. pseudotuberculosis
- C. ulcerans and C. pseudotuberculosis are less common and, unlike C. diphtheriae, are zoônotic, associated with farm/dairy contacts.
- Virulent C. diphtheria strains carry a bacteriophage with the diphtheria toxin gene. Without this bacteriophage, the microbe cannot cause serious disease.
- Nontoxigenic C. diphtheriae can still cause significant invasive disease (e.g., wound infection, bacteremia, endocarditis)
- Culture is best performed on tellurite-selective media, e.g., Tinsdale agar.
- The demonstration of an immunoprecipitation band confirms toxin production.
- CDC provides laboratory support for state/local health departments.
- Elek immunodiffusion assay for C. diphtheriae and C. ulcerans isolates
- CDC provides laboratory support for state/local health departments.
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Last updated: March 12, 2026
Citation
Auwaerter, Paul. "Corynebacterium Diphtheriae (Diphtheria)." Johns Hopkins ABX Guide, The Johns Hopkins University, 2026. Johns Hopkins Guides, www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540144/all/Corynebacterium_diphtheriae__Diphtheria_.
Auwaerter P. Corynebacterium diphtheriae (Diphtheria). Johns Hopkins ABX Guide. The Johns Hopkins University; 2026. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540144/all/Corynebacterium_diphtheriae__Diphtheria_. Accessed April 2, 2026.
Auwaerter, P. (2026). Corynebacterium diphtheriae (Diphtheria). In Johns Hopkins ABX Guide. The Johns Hopkins University. https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540144/all/Corynebacterium_diphtheriae__Diphtheria_
Auwaerter P. Corynebacterium Diphtheriae (Diphtheria) [Internet]. In: Johns Hopkins ABX Guide. The Johns Hopkins University; 2026. [cited 2026 April 02]. Available from: https://www.hopkinsguides.com/hopkins/view/Johns_Hopkins_ABX_Guide/540144/all/Corynebacterium_diphtheriae__Diphtheria_.
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