Diphtheria
Definition
An acute toxin-mediated disease
Caused by Corynebacterium diphtheriae.
Nontoxigenic strains also cause disease - mostly cutaneous and usually mild.
Three biotypes (ie, mitis, gravis, intermedius), each capable of causing diphtheria
Epidemiology
Spreads via contact with airborne respiratory droplets
Contact with exudate from infected skin lesions.
Asymptomatic respiratory carriers +
Age
When diphtheria was endemic, it primarily affected children younger than 15 years;
recently, the epidemiology has shifted to adults
Pathogenesis
Induces local inflammatory reaction.
Produces exotoxin, which inhibits protein synthesis and causes local tissue necrosis.
Diphtheria is endemic in many parts of the world
Clinical Features
Severity of disease due to C diphtheriae depends on :-
The site of infection
The immunization status of the patient
Dissemination of toxin
Initial infection usually is localized and is categorized by the site of involvement.
Tonsils and pharynx: - most common sites
Symptoms
Sore throat
Absence of systemic complaints.
Fever, if it occurs, is usually lower than 102°F
Malaise
Dysphagia
Headache
Membrane formation begins after the 2-day to 5-day incubation period
Grows to involve the pharyngeal walls, tonsils, uvula, and soft palate.
Extend to the larynx and trachea, causing airway obstruction and eventual suffocation.
Throat and neck becomes edematous - bull-neck appearance
Lymphadenopathy develops.
The patient throws the head back to relieve pressure on the throat and larynx.
Swallowing may be made difficult by unilateral or bilateral paralysis of the muscles of the palate.
Circulatory collapse, respiratory failure, stupor, coma, and death.
Larynx: Initial hoarseness may progress to loss of voice and severe respiratory tract obstruction. Nasal diphtheria may present as a common viral upper respiratory tract infection. A foul odor may develop - common in infants.
Skin: Cutaneous diphtheria may occur at one or more sites
Other Problems to be Considered
Vincent angina
Exudative pharyngitis due to Streptococcus pyogenes and Epstein-Barr virus
Lab Studies
Iisolation of C diphtheriae on cultures with toxigenicity testing.
Obtain specimens from the membrane as well as from the nose and throat.
Clinical samples (swabs, pieces of membrane, biopsy tissue) can be transported with cold packs in a sterile empty container
Medical Care
Mechanical ventilation may be inevitable
Specific antitoxin is the mainstay of therapy and should be administered on the basis of clinical diagnosis because it neutralizes free toxin only. Efficacy diminishes with elapsing time after the onset of mucocutaneous symptoms.
Individuals are placed in strict isolation (respiratory tract colonization) or contact isolation (cutaneous colonization only) until at least 2 subsequent cultures taken 24 hours apart after cessation of therapy demonstrate negative results.
Repeat cultures are performed at a minimum of 2 weeks after completion of therapy in patients and carriers; if results are positive, an additional 10-day course of oral erythromycin should be administered and follow-up cultures performed.
Cardiology:
ECG: -
a prolonged PR interval
changes in the ST-T wave
cardiac dysrhythmias : first-degree, second-degree, and third-degree heart block, atrioventricular dissociation, and ventricular tachycardia.
Toxic cardiomyopathy
Myocarditis
Neurology:
Weakness of the posterior pharyngeal, laryngeal, and facial nerves ; difficulty in swallowing, and risk of death from aspiration.
Oculomotor and ciliary paralysis, which manifest as strabismus, blurred vision, or difficulty with accommodation.
Drugs:-
Penicillin
erythromycin
clindamycin
rifampin
tetracycline.
Immunization Protocol: Diphtheria toxoid is almost always given to children together with tetanus toxoid and pertussis vaccine in a shot called DTaP - Triple antigen
DPT - Diphtheria, pertussis, Tetanus vaccine ( pertussis = whooping cough_
Three Doses - at 1½ months, 2½ months, 3½ months
First Booster - at 1½ years
Second Booster - 4 years
Complications
Demyelination of nervous tissue is seen in all fatal cases of diphtheria; paralysis
Prognosis
Depends on
The virulence of the organism (with the gravis strain usually accounting for the most severe disease)
The age and immunization status of the patient
The site of involvement
The speed with which antitoxin is administered. For patients in whom disease is recognized on day 1 and therapy is promptly initiated, the mortality rate is approximately 1%. If appropriate treatment is withheld until day 4, the mortality rate rises to 20%.
