Summary
Highlights
The video introduces Corynebacterium Diphtheriae, highlighting its association with pseudomembranous pharyngitis, skin infections, myocarditis, and peripheral neuritis. It describes the bacterium as a gram-positive, non-spore-forming, aerobic, immotile rod that is catalase-positive and a carbohydrate fermenter.
Corynebacterium Diphtheriae exhibits a club-shaped, pleomorphic morphology with metachromatic granules that cause a beaded appearance, resembling Chinese letters under the microscope. It can cause small zones of hemolysis and grows on tellurite agar.
The diphtheria exotoxin works by ADP-ribosylating and inhibiting elongation Factor 2, which is crucial for protein synthesis. This inhibition stops the cell from making essential proteins, leading to cell dysfunction. High iron concentrations can inhibit the toxin's production by activating a repressor.
The tox protein requires two cleavages to become active; first to remove the leader sequence, then to separate it into active A and binding B subunits, connected by a disulfide bond. The B subunit binds to the host cell receptor, Heparin-binding epidermal growth factor receptor, and facilitates the entry of the catalytic A subunit into the cell.
The diphtheria toxin causes myocarditis and neuritis because the Heparin-binding epidermal growth factor receptor, its target, is present on neurons and myocardial cells, making these tissues particularly susceptible to the toxin's damaging effects. Treatment for diphtheria can include erythromycin.
The diphtheria toxin is an exotoxin, a protein released from the bacterial cell. It is an A-B toxin, where the A subunit is active with enzymatic activity, and the B subunit is for binding to host cell receptors. The gene for this toxin is introduced into the bacterium via a beta prophage.