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Diphtheria – Respiratory tract infection

Diphtheria is a respiratory tract infection.

Agent of infection

Corynebacterium diphtheriae

Organism features

Special features

Virulence factors

Diphtheria toxin (DT)

Mechanism of action

↓ Fragment B binds to host cell receptors

↓ Helps in internalization of fragment A

↓ Fragment A causes ADP ribosylation of elongation factor 2 (EF-2)

↓ EF-2 inhibited

↓ inhibiton of translation (protein sysnthesis)


Bacilli are non-invasive; toxin is resposible for the pathogenesis

1. Respiratory diphtheria

2. Cutaneous diphtheria

3. Systemic complications

Lab diagnosis


Direct smear microscopy

Gram staining:

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