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Diphtheria

Diphtheria is a disease caused by infection with the organism corynbacterium diphtheriae. This organism produces disease by producing a toxin which inhibits ribosomal protein production.

Infection is usually transmitted by droplet infection (aerosol spread).

Clinical manifestations

The incubation period is about a week.

4 types of clinical presentation:

  1. Nasal diphtheria: manifests by unilateral nasal discharge.
  2. Pharyngeal diphtheria: this manifests by marked tonsillar and pharyngeal inflammation and the formation of a tough grey-white pseudomembrane which is firmly adherent to the underlying tissues. The membrane is formed by debris resulting from the inflammatory process and contains fibrin, pus cells, epithelial cells, bacteria among other things. Regional lymphadenopathy may result in the "bull's neck" appearance.
  3. Laryngeal diphtheria: is a dangerous development and results from the extension of the membrane from the pharynx onto the larynx. This leads to the development of a husky voice, brassy cough and may result in fatal dyspnea and cyanosis due to respiratory obstruction.
  4. Cutaneous diphtheria: This presents as a punched out ulcer with undermined edges which is covered by a grey-white adherent membrane. Cutaneous diphtheria appears mainly in association with burns and in individuals that lack personal hygiene.

The exotoxin leads to myocarditis, and neurolgical complications (paralysis from the palate downwards).

Diagnosis

The diagnosis is confirmed by taking a stained smear from throat swabs and a bacterial culture. The results should be waited for and antitoxin therapy started immediately as soon as the diagnosis of diphtheria is in question.

Treatment

Antitoxin therapy is the only specific treatment available and must be administered as soon as possible.

Procaine penicillin is given for 7 days to eliminate the organisms and thereby prevent more toxin production.

Prevention and immunization

Active immunization is usually given in childhood in the form of diphtheria toxoid. It is usually given with tetanus and pertussis vaccines (the so called DPT vaccine). DPT is started at the age of 3 to 4 months and is given in 3 doses a month apart. A booster dose (DT) is given on school entry.

Contacts of infected individuals should have a throat swab examined. Those with positive results should be treated with penicillin or erythromycin and be given a booster dose of the toxoid. 

Case classification

Probable: a clinically compatible case that is not laboratory confirmed and is not epidemiologically linked to a laboratory-confirmed case

Confirmed: a clinically compatible case that is either laboratory confirmed or epidemiologically linked to a laboratory-confirmed case

From the CDC guidelines: Cutaneous diphtheria should not be reported. Respiratory disease caused by nontoxigenic C. diphtheriae should be reported as diphtheria. All diphtheria isolates, regardless of association with disease, should be sent to the Diphtheria Laboratory, National Center for Infectious Diseases, CDC.

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