Diphtheria

A36.9

*Notifiable condition

• Description
• Diagnostic criteria
• General and supportive measures
• Medicine treatment
• Referral

DESCRIPTION

Diphtheria is an acute, communicable infection of the upper respiratory tract, caused by Corynebacterium diphtheriae. Disease is unlikely if the patient shows documented evidence of complete immunisation. Cutaneous diphtheria can also occur. Incubation period is between 2 and 7 days.

Complications include:

• In the first 2 weeks of the disease:
  • Cervical lymphadenopathy with peri-adenitis and with swelling of the neck (bull neck).
  • Upper airway obstruction by membranes.
  • Myocarditis.
• Usually after 3 weeks:
  • Neuritis resulting in paresis/paralysis of the soft palate and bulbar, eye, respiratory and limb muscles.

DIAGNOSTIC CRITERIA

Clinical

Any person presenting with: pharyngitis, nasopharyngitis, tonsillitis, laryngitis, tracheitis (or any combination of these), where fever is absent or low-grade.
AND
One or more of the following:

• Adherent pseudomembrane which bleeds if manipulated or dislodged.
• Features suggestive of severe diphtheria, including: stridor, bull-neck, cardiac complications (myocarditis, acute cardiac failure and circulatory collapse), acute renal failure.
• Link to a confirmed case.

Investigations

• Nasal or pharyngeal swab: Microscopy and culture.
• Culture of membrane.
• Important: Inform the laboratory that specimen is from a patient with suspected diphtheria.

GENERAL AND SUPPORTIVE MEASURES

• Staff in direct contact with patient should wear protective mask (N-95).
• Isolate patient in high or intensive care unit until 3 successive nose and throat cultures at 24-hour intervals are negative.
• Usually non-communicable within 4 days of antibiotics.
• Nutritional support.
• If respiratory failure develops, provide ventilatory support.
• Tracheostomy if life-threatening upper airway obstruction.
• Bed rest for 14 days.

MEDICINE TREATMENT

Note: Do not withhold treatment pending culture results.

Antibiotic therapy (must be given for a total of 14 days)

Parenteral treatment for patients unable to swallow: Switch to oral as soon as patient able to swallow:

• Benzylpenicillin, IV, 50 000units/kg/dose 12 hourly.

Oral treatment for patients able to swallow:

• Phenoxymethylpenicillin, oral, 15mg/kg/dose 6 hourly.
• Maximum: 500 mg per dose.

In severe penicillin allergy:

Parenteral treatment for patients unable to swallow: Switch to oral as soon as patient able to swallow:

• Azithromycin, IV, 10 mg/kg daily.

Oral treatment for patients able to swallow:

• Azithromycin, oral, 10 mg/kg daily.

Diphtheria antitoxin treatment (DAT):

DAT should be given to all probable classic respiratory diphtheria cases without waiting for laboratory confirmation. DAT neutralises circulating unbound diphtheria toxin and prevents progression of disease; delaying administration increases mortality. The dosing of DAT is product-specific; refer to package insert.

Close contacts (household and regular visitors):

Regardless of immunisation status, isolate contact and swab throat for culture. Keep under surveillance for 7 days. Give antibiotic prophylaxis as follows:

Prophylactic treatment for contacts:

In severe penicillin allergy:

All close contacts:

If 1ˢᵗ culture was positive, follow up throat culture after 2 weeks and treat again.

REFERRAL

• All.