Corynebacterium

1883: Klebs recognizes the pathogen as rods in diphtheric membranes. 1884: Löffler succeeds in pure culture with the "Löffler serum" named after him. 1888: Roux and Yersin, Pasteur Institute, Paris, discover the diphtheria toxin in germ-free culture filtrates.

The genus Corynebacterium (from Greek koryne = club - due to the unilateral or bilateral club-shaped distension of the bacterium) includes in water and soil native, partly aerobic, partly anaerobic, gram-positive, short, straight or slightly curved, unflagellated and thus immobile rods of the bacterial family Corynebacteriaceae, often with club-like thickened ends. They do not possess a capsule. Corynebacteria otherwise show the structure of gram-positive bacteria. However, the cell wall contains mycolic acid, which is otherwise found only in mycobacteria and Nocardia . In the cell plasma of the bacteria, so-called polar bodies are found, which contain polyphosphates and calcium. These polar bodies are difficult or impossible to visualize with the Gram stain, which is why the Neisser stain is used for this purpose. After staining, the bacteria appear yellow to pink, while the polar bodies are dark blue to black. Nowadays, this staining method is mainly used for the diagnosis of Corynebacterium diphteriae and pseudodiphteriticum.

Corynebacteriaceae do not form spores or capsules. Another morphological feature of Corynebacteriaceae is a V-shaped connection between mother and daughter cell after cell division. This shape is formed by what is known as snapping postfission movement. This snapping division is caused by the fact that only the inner cell wall of the corynebacteria participates in cell division. Corynebacteria are reliably killed by heat (10 min at 58°C) and by commercial disinfectants. They are relatively resistant to desiccation.

Corynebacteria are cultivated on blood agar and can be obtained from sputum, gastric juice, laryngeal swab, urine and even ejaculate or menstrual blood. The growth time until macroscopic colonies become visible is about 18 - 24 hours. The biochemical reactions are then used to distinguish between pathogenic and apathogenic corynebacteria. Pathogenic species are characterized by positive catalase reaction, negative urease reaction, fermentative degradation of glucose (but not sucrose) and nitrate reduction.

Only corynebacteria infected with a specific phage cause disease. This phage carries the tox+ gene for the exotoxin. The tox+ gene is part of the prophage β and is integrated into the bacterial chromosome by transduction. First, the bacterium binds to the host cell. Then, the A toxin is taken up into the cell in a vacuole. Diphtheria toxin A then inhibits elongation factor 2 by ADP-ribosylation of a specific amino acid residue called diphthamide. Some strains of Corynebacterium ulcerans also carry this phage and are thus pathogenic and diphtheria-causing.

Transmission of Corynebacterium diphtheriae occurs exclusively from person to person by droplet infection, other secretions, or direct contact. Often, due to good vaccination coverage in Germany, infection occurs in subtropical areas where diphtheria is endemic. The incidence of diphtheria in Central Europe is about 0.001/100,000 per year. Dogs and cats are natural reservoirs of toxigenic Corynebacterium ulcerans strains. Apathogenic species belong to the normal flora of the skin and mucosa.

The genus Corynebacterium is diverse; some representatives are pathogenic to humans or animals. Others are saprophytes and live on decaying plant remains. Some species are commonly found in the mucosal flora and on the skin of humans. The most medically significant species is Corynebacterium diphtheriae . Other species of this genus (diphtheroid species) can colonize skin and mucosa as saprophytes. They are becoming increasingly important as opportunistic pathogens. Especially in immunocompromised people they are feared as pathogens of wound infections, endocarditis or sepsis.

• Corynebacterium diphtheriae (Corynebacterium diphtheria -gravis, intermedius, mitis): Diphtheria
• Corynebacterium ulcerans: diphtheria-like symptoms(skin diphtheria)
• Corynebacterium jeikeium: sepsis, endocarditis soft tissue infections
• Corynebacterium urealyticum cystitis (alkaline incrusted stones)
• Corynebacterium pseudodiphtheriticum: facultative pathogen, endocarditis, respiratory tract infection
• Corynebacterium tenuis: skin/mucous membrane flora, keratoma sulcatum
• Corynebacterium amycolatum: skin/mucous flora, device-associated infections
• Corynebacterium striatum: skin/mucous membrane flora
• Corynebacterium minutissimum skin flora: Erythrasma
• Corynebacterium matruchotii: oral mucosal flora, eye infections
• Versch. Corynebacteria (not further differentiated): Trichobacteriosis axillaris

Corynebacteria are sensitive to antibiotics (e.g. penicillin G, erythromycin, macrolides and fusidic acid). Treatment is systemic or topical, depending on the disease.

In Germany, the direct or indirect detection of toxin-forming Corynebacteria is notifiable by name according to § 7 of the Infection Protection Act, insofar as the detection indicates an acute infection. In Switzerland, a positive laboratory-analytical result (or a negative result in the case of a toxin gene test) for the pathogen Corynebacterium diphtheriae and other toxin-forming Corynebacteria (C. ulcerans, C. pseudo-tuberculosis) is notifiable under the Epidemics Act (EpG) in conjunction with the Epidemics Ordinance and Annex 3 of the FDHA Ordinance on the Notification of Observations of Communicable Human Diseases.