All about Bacterial Infections Caused by Gram-Positive Corynebacterium diphtheriae with diagnosis Treatment Signs and symptoms

Diphtheria (from the Greek word for leather which refers to the tough pharyngeal membrane that is the clinical hallmark of infection) is an acute, communicable disease caused by the gram-positive bacillus Corynebacterium diphtheriae. The membrane is created by a thick, inflammatory exudate. A rare bacterial infectious disease marked by the formation of a membrane over the tonsils, uvula, soft palate, and posterior pharynx and occasionally on the skin.

Clinical features:DIPHTHERIA


  • it is caused by Corynebacterium diphtheriae.It may be anterior nasal, faucial, laryngeal. Skin and conjunctiva may also be involved.
  • The bacteria produces an exotoxin which forms a grey membrane over the tonsils, pharynx, larynx. There is congestion, edema, local tissue destruction, and en largement of regional lymph nodes.
  • There are features of toxaemia.
  • The exotoxin can cause myocarditis and nerve dam age leading to paralysis.
  • Mortality is 10%.
  • The bacteria may be gravis, mitis, intermedius. The gravis bacteria produces severe infections. Source of infection is a case with running nose.


  • Symptomatic diphtherial infection results from two factors: Local noninvasive inflammation of the respiratory tract or skin Local and systemic effects of a potent diphtheria exotoxin

Period of infectivity:

  • 14 – 28 days from onset of disease.

  • 1-5 years
  • Immunity is high in the population Incubation period 2 – 6 days.

Clinical features:DIPHTHERIA

  • It is common to base a presumptive diagnosis upon initial clinical features of the illness.
  • There is a membrane on the tonsils and pharynx.
  • The earliest pharyngeal finding is generally mild erythema.
  • Diphtheria should be considered in patients with pharyngitis, low-grade fever and/or cervical adenopathy.
  • This typically progresses to areas of white exudate, which coalesce to form an adherent gray pseudomembrane that bleeds with scraping.
  • Both culture of C. diphtheriae and a positive toxin-production assay are required for confirmation of the diagnosis.
  • Affects the tonsils, pharynx, larynx, nasal passages. There is sore throat, difficulty in swallowing, low grade fever.
  • There is hoarseness and shrill cough.
vSchick test
Schick test DIPHTHERIA


Schick test DIPHTHERIA

  • Definitive diagnosis of diphtheria requires isolation of C. diphtheriae from respiratory tract secretions or cutaneous lesions.
  • This is an intradermal test for antitoxin and hyper sensitivity.
  • An intradermal Schick test toxin is injected into the forearm and inactivated toxin is injected into the other arm as control.
  • A negative reaction is seen in immune persons.
  • A positive reaction is a red flush of 1-5 cm. in one or two days in the test arm.
  • A pseudopositive reaction is a red flush in both the arms.
Clinical features:DIPHTHERIA of skin


Treatment of Diphtheria :

  • The treatment of respiratory diphtheria combines administration of diphtheria antitoxin with antibiotic therapy
  • Diphtheria antitoxin 50,000 unit 1M / IV
  • Penicillin 2.5 lakhs unit 6 hrly or erythromycin 250 mg 6 hrly for 5 days
  • Carriers are given erythromycin for 10 days. Diphtheria antitoxin in horse serum 10,000 – 1,00,000 units intramuscular in 2 doses.
Vaccination of Diphtheria, DPT


Vaccination of Diphtheria:
  • DPT – Diphtheria, Pertussis, Tetanus is given as-l  doses at 4-week intervals and booster at 2 years given
  • Fever may occur after vaccination.
  • Supportive measures including electrocardiographic monitoring and careful airway management are also important due to the risk of myocarditis and airway obstruction.


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