Diphtheria

Question 1

Diphtheria - organism

Answer 1

Corynebacterium diphtheriae
Aerobic gram positive rod with pleomorphic, metachromatic polar granules

Question 2

Diphtheria - types of infection

Answer 2

Upper respiratory tract infection
Cutaneous infection

Question 3

Diphtheria - transmission

Answer 3

Droplets, secretion and fomites

Question 4

Diphtheria - incubation period

Answer 4

IP 2-5 days

Question 5

Diphtheria - infectious period

Answer 5

Without antibiotics = communicable for 2-6 weeks
With antibiotics = 48hrs

Question 6

Diphtheria = pathophysiology

Answer 6

Primarily exotoxin mediated disease:
-Death of mucosal epithelial cells - release grey fibrinous pseudo-membrane which bleeds on contact
-Adjacent tissue becomes inflamed - gross lymphadenopathy
-Respiratory failure due to airway obstruction or aspiration of pseudo-membrane

Lymphatic and haematogenous toxin spread:
-Myocarditis [2-7 weeks]
-Neuropathy and paralysis [1-3 months]
-Renal failure
-Disseminated disease - shock - MOF

Question 7

Diphtheria - case definition

Answer 7

Illness characterised by laryngitis or pharyngitis or tonsillitis
AND
adherent membrane of tonsils, pharynx and/or nose or gross lymphadenopathy

Question 8

Diphtheria - clinical course

Answer 8

Catarrhal:
-Erythema of pharynx
-No membrane

Follicular
-Patches of exudates over pharynx and tonsils

Spreading
-Membrane is formed covering the tonsil and posterior pharynx

Combined
-More than one anatomical site involved

Question 9

Diphtheria - pseudo-membrane appearance

Answer 9

Confluent sharply demarcated, tightly adherent and dark grey
-Initially isolated spots of grey or white exudate in tonsillar and pharyngeal area
-Spots coalesce within a day to form pseudo-membrane that becomes progressively thicker
-Extends beyond margins of tonsils [streptococcal infection are white membrane limited to tonsillar area]

Five possible areas = tonsils x2, uvula, nasopharynx, oropharynx
-Simple = one area only
-Extensive = two or more areas

Question 10

Diphtheria - management

Answer 10

Isolation - standard droplet and contact precautions

Diphtheria antitoxin [DAT]
-Equine serum product
-Dose by disease severity not site of patient [20,000 - 80,000 units]
-Risks = anaphylaxis, febrile reaction, serum sickness
-Sensitisation testing [Besredka method]

Antibiotics following DAT:
-Penicillin or erythromycin

Supportive therapy for complications

Vaccination