Pathogens

Corynebacteria – Infection, Transmission & Diseases

Corynebacterien

Corynebacteria are Gram-positive, rod-shaped bacteria . They are immobile and grow under both aerobic and anaerobic conditions. One of their species is responsible for diphtheria , among other things .

What are Corynebacteria?

Corynebacerium is a genus of gram-positive, rod-shaped bacteria that can grow facultatively anaerobically, that is, they can exist in the presence of oxygen as well as in the absence thereof. Their species are immobile and do not form spores. They are also catalase positive and oxidase negative. In addition, the corynebacteria only grow under demanding conditions, namely at 37 ° C and the presence of 5 % CO2.

Corynebacteria have a large variety of species. Some species are pathogenic to humans (like the C. diphtheriae ), other species are saprophytes, meaning they live on dying plant debris. Still others are non-pathogenic species which occur in the normal flora on the skin and mucous membranes of humans.

The club-shaped swelling at one end is characteristic of the corynebacteria, which is how they got their name (gr. koryne = club). Another special feature of Corynebacteria is the presence of mycolic acids in the cell wall, which is also found in mycobacteria .

Occurrence, Distribution & Properties

Non-pathogenic types of corynebacteria are mainly found in the normal flora of the skin and mucous membranes of humans. However, pathogenic species are also widespread and found worldwide. The most common infectious disease caused by a Corynebacterium is diphtheria. Transmission occurs exclusively from person to person and can occur through droplet or smear infection .

If a person is infected with a Corynebacterium, local pathogen colonization follows after an initial infection. The pathogen can then spread or, in the case of C. diphtheriae, for example, an exotoxin is formed that inhibits protein synthesis. The incubation period ranges from 2 to 10 days. In general, corynebacteria are rarely the cause of a disease, especially since there is good vaccination protection in Germany. Exceptions are diphtheria, which is endemic to Russia, and Corynebacterium minutissimum.

Corynebacteria are gram-positive rod-shaped bacteria. They exhibit a degree of pleomorphism, meaning they are able to change shape depending on environmental conditions. They contain mycolic acid in their cell wall and are catalase-positive but oxidase-negative. Corynebacteria can be stained with Neisser staining and show yellow-brown bacteria with black-blue polar bodies.

Meaning & Function

There are numerous types of corynebacteria that are found on the normal flora of the skin and mucous membranes. These include C. minutissimum, C. xerosis, C. pseudotuberculosis, C. jeikeium, C. pseudodiphteriticum and Corynebacterium bovis. Some species are referred to as facultative pathogens because they can trigger diseases under certain conditions, for example a weakening of the immune system .

These species include C. minutissimum, the causative agent of erythrasma , and C. jeikeium, a possible causative agent of sepsis . The physiologically present corynebacteria break down the fats that are secreted by the sebaceous glands into fatty acids. These are then responsible for the acidic environment of the skin and mucous membranes, which forms part of the protective acid mantle. This is a weakly acidic pH that is found on the epidermis and thus creates a bactericidal effect on pathogens, which leads to inhibition of germ growth. Corynebacteria thus form part of the innate, non-specific immune system. In addition, the C. striatum is said to be partly responsible for the typical axillary odor.

Diseases & Ailments

The Corynebacteria describe a genus of bacteria characterized by many species. The most important pathogenic species is C. diphtheriae. This is the causative agent of diphtheria. Humans are the only host of this bacterium and usually transmit the pathogen by droplet infection . The C. diphtheriae then often enters the throat, more rarely in skin wounds and multiplies there. After multiplying, it produces the diphtheria toxin, which comes from the bacteriophage . Bacteriophages are viruses that infect bacteria.

Diphtheria toxin works by inhibiting protein synthesis. A dose of 100-150 ng per kg of body weight is enough to kill a human. First, there is a local effect in the throat of the affected person. The epithelial cells of the mucous membrane are destroyed, bleeding and fibrin excretion occur. The latter form the characteristic fibrin coatings on the infected mucosa, which is referred to as the pseudomembrane. Other bacteria, as well as cells and blood cells, become trapped in the pseudomembranes.

Classic pharyngeal and larynx diphtheria is also characterized by fever , swelling of the lymph nodes and soft palate paresis. Dreaded complications are myocarditis , nerve and kidney damage if the toxin spreads systemically.

Laryngitis diphthericae used to be a dreaded complication that quickly led to death by asphyxiation. It was characterized by a Caesar’s neck (severe lymph node swelling) and a sweetish bad breath. In addition to C. diphtheriae, other related species can also cause diphtheria, such as C. ulcerans, which can also affect animals.

 

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.