University:
Eastern Kentucky University
Course:
BIO 273 | Clinical Microbiology
Academic year:

2022
Views:

126

Pages:

2
Author:

Alexa Livingston

Corynebacterium Diphtheriae (+) Features: 1. Club-shaped (V or Y formation) 2. Contains metachromatic granules a. These dye red with aniline dye b. Rest of the cell stays blue Transmission: 1. Respiratory droplets Pathogenesis: 1. Diphtheria toxin has two components a. A subunit is active b. B subunit is binding 2. Toxin causes ADP ribosylation of elongation factor 2 (EF-2) a. This leads to inhibition of ribosomal function and hence, inhibition of protein synthesis b. Also, it leads to production of dirty gray exudate which forms a pseudomembrane on oropharynx mucosa Diseases: 1. Diphtheria has following characteristics a. Pseudomembrane i. May spread to larynx and trachea and cause airway obstruction ii. May also cause lymphadenopathy (Bull’s neck) 2. Cardiotoxicity a. Myocarditis b. Arrhythmia c. Heart block 3. Local Paralysis: a. Starts in posterior pharynx (Myelin damage) b. May lead to other cranial nerve deficits c. Mechanism involves attack of toxin on myelin sheath of nerve fibres Lab Diagnosis: 1. Swab pseudomembrane on following: a. Tellurite agar b. Loeffler’s medium 2. Elek’s test a. To differentiate between toxic and non-toxic strains i. In vitro assay on filter paper that has anti-toxin ii. If toxin binds, there is a reaction and the test is positive i.e. the strain is toxic Prevention: 1. Toxoid vaccine a. Inactivated exotoxin conjugated with protein to increase immune response b. Powerful IgG response c. Often given with vaccines of Clostridium tetani and acellular pertussis (DTaP) Treatment: 1. Passive immunity (Antitoxin)