Diphtheria (Corynebacterium diphtheriae)

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Corynebacteria are Gram-positive, aerobic, nonmotile, rod-shaped bacteria related to the

Actinomycetes. They do not form spores or branch as do the actinomycetes, but they

have the characteristic of forming irregular shaped, club-shaped or V-shaped

arrangements in normal growth. They undergo snapping movements just after cell

division which brings them into characteristic arrangements resembling Chinese letters.

The genus Corynebacterium consists of a diverse group of bacteria including animal and

plant pathogens, as well as saprophytes. Some corynebacteria are part of the normal flora

of humans, finding a suitable niche in virtually every anatomic site. The best known and

most widely studied species is Corynebacterium diphtheriae, the causal agent of the

disease diphtheria.

History and Background

No bacterial disease of humans has been as successfully studied as diphtheria. The

etiology, mode of transmission, pathogenic mechanism and molecular basis of exotoxin

structure, function, and action have been clearly established. Consequently, highly

effective methods of treatment and prevention of diphtheria have been developed.

The study of Corynebacterium diphtheriae traces closely the development of medical

microbiology, immunology and molecular biology. Many contributions to these fields, as

well as to our understanding of host-bacterial interactions, have been made

studying diphtheria and the diphtheria toxin.

Hippocrates provided the first clinical description of diphtheria in the 4th century B.C.

There are also references to the disease in ancient Syria and Egypt.

In the 17th century, murderous epidemics of diphtheria swept Europe; in Spain 'El

garatillo' (the strangler'), in Italy and Sicily, 'the gullet disease'.

In the 18th century, the disease reached the American colonies and reached epidemic

proportions in 1735. Often, whole families died of the disease in a few weeks.

The bacterium that caused diphtheria was first described by Klebs in 1883, and was

cultivated by Loeffler in 1884, who applied Koch's postulates and properly identified...