Corynebacterium diphtheriae (C. Diphtheriae)

Diphtheria is a bacterial infection caused by C. diphtheriae.19 C. diphtheriae is transmitted from person to person usually through respiratory droplets generated by coughing or sneezing. A person can also get infected by contact with contaminated objects. Rarely, C. diphtheriae is shed from skin lesions or contaminated clothes. The incubation period of diphtheria is 2-5 days (range: 1-10 days).

Clinical Features

C. diphtheriae commonly infects respiratory mucosa and skin. Consequently, infections may be conveniently classify as respiratory diphtheria (e.g., anterior nasal, pharyngeal, tonsillar, and laryngeal) and cutaneous diphtheria. The typical clinical features of diphtheria are caused by C. diphtheriae toxins. The “hallmark” sign of diphtheria is a thick, gray pseudomembrane (formed from dead tissue caused by the toxins) covering the throat and tonsils.

Other clinical manifestations may include a sore throat, dysphagia, hoarseness, enlarged lymph nodes, difficulty breathing, nasal discharge, fever, and chills. The toxins may be absorbed into the systemic circulation and cause inflammation of the heart muscles (myocarditis), the kidneys, and the nervous system (polyneuropathy). Diphtheria can cause airway blockage, which may lead to pneumonia and/or respiratory failure.


Diphtheria is a vaccine-preventable infection. There are four combination vaccines available to prevent diphtheria, tetanus and pertussis: DTaP, Tdap, DT, and Td. Two of these (DTaP and DT) are given to children younger than 7 years of age, and two (Tdap and Td) are given to older children and adults. Each of these vaccines prevents diphtheria and tetanus, and DTaP and Tdap vaccines also prevent pertussis. A booster dose of Td is recommended every 10 years.

Medical Management

Diphtheria is treated with antibacterial agents (erythromycin or procaine penicillin G) and the administration of diphtheria antitoxin (obtained from CDC on request). Patients are usually kept in isolation, until they are no longer infectious (about 48 hours after effective antibacterial treatment begins). Airway maintenance and respiratory support may be required. The overall case-fatality rate for diphtheria is 5% to 10%.