Corynebacterium diptheriae
| Categorization | |
|---|---|
| Cell Wall: Gram Positive | Shape: Rod, Non-sporulating |
| Metabolism: Facultative Anaerobe | |
| Culture and Detection |
|---|
- Organism grows on Tellurite agar selective media, allowing detection from a nasopharyngeal swab.
| Virulence Factors |
|---|
- Diptheria Toxin
- Diptheria Toxin is an exotoxin that synthesized only by C. diptheriae that have undergone lysogenic transduction with a phage that contains the toxin gene. Diptheria Toxin is similar to a classic A-B Toxin.
- The B Subunit binds to host cells and induces internalization of the toxin
- The A Subunit is the toxic subunit and binds a ribosomal Elongation Factor, thus inhibiting protien translation, eventually leading to cell death.
| Transmission |
|---|
- Is transmitted in aerosolized droplets between humans which are its only hosts.
| Clinical Consequences |
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- Pharyngeal Infection
- C. diptheriae first colonizes and infects the pharynx causing necrosis of mucosal epithelial cells. This can be observed as an ulceration covered by a greyish/blackish "Pseudomembrane" composed of dead epithelial cells, dead neutrophils, and fibrin.
- Complications
- Toxin produced by pharyngeal C. diptheriae can then enter the blood stream, be spread systemically, and damage a variety of organs. Damage to the heart can result in a myocarditis while damage to peripheral nerves can cause peripheral neuropathy.
| Incidence |
|---|
- Historically, Diptheria was mostly observed in children.
| Prevention |
|---|
- DPT vaccine: One component of this vaccine (DPT) is the inactivated, formalin-fixed Diptheria Toxin which results in humoral immunity and thus inactivating antibodies to the toxin.
| Treatment |
|---|
- Antitoxin: An antibody which binds Diptheria Toxin and is very effective
- Antibiotics: Mostly used to prevent transmission and are not useful for preventing symptomology once it has arisen. Penicillin G or erythromycin are commonly used.