Corynebacterium

A genus of bacteria that includes important pathogens

Corynebacterium ulcerans under a microscope

Corynebacterium is a genus of bacteria that are gram-positive, aerobic, and non-motile. These bacteria are characterized by their club-shaped appearance and are part of the Actinobacteria phylum. The genus includes several species, some of which are pathogenic to humans and animals.

Characteristics

Corynebacterium species are known for their distinctive rod-like shape, often described as "club-shaped" due to their swollen ends. They are gram-positive, meaning they retain the crystal violet stain used in the Gram staining procedure. These bacteria are non-motile and do not form spores. They are aerobic, requiring oxygen for growth, and are catalase-positive, which means they produce the enzyme catalase.

Pathogenic Species

Several species within the Corynebacterium genus are known to cause diseases in humans and animals. The most notable pathogenic species is Corynebacterium diphtheriae, the causative agent of diphtheria, a serious respiratory disease. Other species, such as Corynebacterium ulcerans and Corynebacterium pseudotuberculosis, can also cause infections in humans and animals.

Corynebacterium diphtheriae

Corynebacterium diphtheriae is the most well-known species due to its role in causing diphtheria. This disease is characterized by the formation of a thick pseudomembrane in the throat, which can lead to breathing difficulties. The bacteria produce a potent toxin that can cause damage to the heart and nervous system.

Corynebacterium ulcerans

Corynebacterium ulcerans colonies on a culture plate

Corynebacterium ulcerans is similar to C. diphtheriae in that it can produce a diphtheria-like toxin. It is primarily an animal pathogen but can infect humans, causing symptoms similar to diphtheria. Infections are often associated with contact with animals or consumption of unpasteurized dairy products.

Corynebacterium pseudotuberculosis

Corynebacterium pseudotuberculosis is primarily an animal pathogen, causing caseous lymphadenitis in sheep and goats. It can occasionally infect humans, leading to skin infections and lymphadenitis.

Ecology

Corynebacterium species are widely distributed in nature. They are commonly found in soil, water, and as part of the normal flora of the skin and mucous membranes of humans and animals. While many species are harmless commensals, some can become opportunistic pathogens under certain conditions.

Laboratory Identification

In the laboratory, Corynebacterium species can be identified by their characteristic morphology and staining properties. They are often cultured on selective media and identified based on biochemical tests. Molecular methods, such as PCR, can also be used for more precise identification.

Related pages

• Diphtheria
• Gram-positive bacteria
• Actinobacteria