Corynebacterium diphtheriae
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Bacteria - Gram Positive
- Staph aureus: Overview
- Staph aureus: Presentation
- Methicillin-Resistant Staph aureus (MRSA)
- Staph saprophyticus
- Strep pneumoniae: Overview
- Strep pneumoniae: Presentation
- Strep viridans
- Strep pyogenes: Overview
- Strep pyogenes: Presentation
- Strep agalactiae
- Strep bovis
- Enterococcus
- Bacillus anthracis
- Bacillus cereus
- Clostridium tetani
- Clostridium perfringens
- Clostridium botulinum
- Clostridium difficile
- Corynebacterium diphtheriae
- Listeria monocytogenes
- Nocardia
- Actinomyces
Corynebacterium diphtheriae
- Characteristics
- Gram + rods
- club-shaped
- Metachromatic (blue-red) granules
- intracellular polyphosphate granules visualized with methylene blue stain on Loeffler medium
- Elek test positive
- Tests for the diphtheria toxin
- Black colonies on cystine-tellurite agar
- Occur in angular arrangements
- Gram + rods
- Diphtheria toxin
- Exotoxin encoded by beta-prophage (Tox gene)
- Derived from Corynephage beta bacteriophage
- Therefore, not all strains of C. diphtheriae are pathogenic
- Also known as AB toxin, composed of 2 subunits
- B (binding) subunit allows penetration of A (active) subunit into the cell
- Inactivates EF-2 (elongation factor) via ADP-ribosylation
- Inhibits protein synthesis, leading to cell death and necrosis
- Similar to Pseudomonas exotoxin A
- Exotoxin encoded by beta-prophage (Tox gene)
- Symptoms
- Pseudomembranous pharyngitis
- grayish-white pseudomembrane
- Bleeds easily if irritated
- Myocarditis
- Can progress to a dilated cardiomyopathy (most common cause of death!) or precipitate arrhythmias
- Polyneuropathy (peripheral neuropathy)
- Lymphadenopathy (bull neck)
- Pseudomembranous pharyngitis
- Treatment
- Diphtheria antitoxin
- Passive immunization (antibodies against toxin)
- Erythromycin
- Penicillin G
- Diphtheria antitoxin