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Description:Under a magnification of 1125X, this Giemsa-stained photomicrograph revealed the presence of Gram-positive Corynebacterium sp. bacteria. Some species of the genus Corynebacterium, are actually a part of the normal population of human skin flora, however, one specie, Corynebacterium diphtheriae, causes an upper respiratory tract illness known as “diphtheria”.


Clinical Features

Respiratory diphtheria presents as a sore throat with low-grade fever and an adherent membrane of the tonsils, pharynx, or nose. Neck swelling is usually present in severe disease. Cutaneous diphtheria presents as infected skin lesions which lack a characteristic appearance.

Etiologic Agent

Toxin-producing strains of Corynebacterium diphtheriae.


Direct person- to-person transmission by intimate respiratory and physical contact. Cutaneous lesions are important in transmission.

Approximately 0.001 cases per 100,000 population in the U.S. since 1980; before the introduction of vaccine in the 1920s incidence was 100-200 cases per 100,000 population. Diphtheria remains endemic in developing countries. The countries of the former Soviet Union have reported >150,000 cases in an epidemic which began in 1990.


Myocarditis, polyneuritis, and airway obstruction are common complications of respiratory diphtheria; death occurs in 5%-10% of respiratory cases. Complications and deaths are much less frequent in cutaneous diphtheria.

Risk Groups

In the pre-vaccine era, children were at highest risk for respiratory diphtheria. Recently, diphtheria has primarily affected adults in the sporadic cases reported in the U.S. and in the large outbreaks in Russia and New Independent States of the Former Soviet Union.

High Resolution: Click here for hi-resolution image (6.6 MB)
Content Providers(s):CDC/ Dr. W. Kaplan
Creation Date:1972
Photo Credit:
Links:CDC - National Center for Immunization and Respiratory Diseases: Division of Bacterial Diseases: Diphtheria
CDC Organization
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Copyright Restrictions:None - This image is in the public domain and thus free of any copyright restrictions. As a matter of courtesy we request that the content provider be credited and notified in any public or private usage of this image.