History

Perhaps the best-known Corynebacterium is Corynebacterium diphtheriae which causes diphtheria. Diphtheria is one of the most well-studied bacterial infections, causing respiratory and cutaneous diseases.

The common presentation of diphtheria is a white to grayish-green pseudo-membrane in the nasopharyngeal area. Symptoms often include sore throat, low-grade fever, and a "bull neck", where the neck of the patient is extremely swollen due to lymphadenopathy.

Cutaneous lesions with a similar grayish membrane may also occur. Initial vesicles or pustules are known to develop into painful lesions and nonhealing ulcers.

Transmission between humans occurs through respiratory droplets or secretions and contact with open lesions. The bacteria is not invasive but rather the exotoxin produced by the bacteria causes tissue necrosis by blocking protein synthesis. This exotoxin may cause serious damage to the heart, kidneys, and peripheral nerves. Traditionally, C. diphtheria nomenclature has broken the species down into four biotypes (or biovars):

C. ulcerans and C. pseudotuberculosis are also both known to be able to produce this exotoxin. (Diphtheria toxin is known as DT). Thanks to advances in molecular biology, several recently described new species may also be capable of producing this DT: C. rouxii and C. silvaticum.⁴

Non-diphtherial corynebacteria have also been described over the years. Once thought to represent skin flora contamination, these are now known to cause skin and soft tissue infections in humans and farm animals.