8. Microbiology
        8.2. Gram-positive bacilli/rod
            8.2.1. Corynebacteria
8.2.1.1. Corynebacterium diphtheriae

Corynebacteria Diphtheriae

Causes diphtheria

Characteristics/Epidemiology

Found in throat and nasopharynx of carriers and patients.

 

 

Pathogenesis/Transmission

Spready by respiratory droplets, less commonly by direct contact or contaminated fomite.

Exotoxin

Clinical significance

1. Upper respiratory tract infection

Infection produces thick, grayish, adherent exudate (pseudomembrane) in the throat.

2. Cutaneous diphtheria

Colonisation and exotoxin production may (but rarely) cause tissue degneneration and death.

Laboratory identification

Corynebacterium can be isolated with selective medium (e.g. Tinsdale's agar - contains potassium tellurite)

Diagnosis is clinical. No fast, reliable lab test is available.

Definitive diagnosis requires culture and tested for virulence.

Treatment

Prompt neutralisation of toxin, then eradication of organism.

First treat with horse serum antitoxin first, then antibiotics.

First line: Erythromycin

Second line: Penicillin G

Prevention/immunity

Formalin treatment of the toxin produces a toxoid - same antigenicity but not toxicity -> thus used to immunisation

Prevention - by immunisation (usually with tetanus toxoid and pertussis antigen i.e. DTPa)

Booster injection - every 10 years.

 


Things to revise/add later:

Bibliography: LWW microbiology


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