What kind of bacteria is Corynebacterium diphtheria?

Corynebacterium diphtheria was first discovered in 1884 by Edwin Klebs and Friedrich Loffler. It is a long, Gram – positive, nonmotile, aerobic bacterium, which is typically found in soil. It is rod – shaped and toxin – producing bacteria. Narrow angels and parallel localization of these microorganisms give them a characteristic form like Chinese characters.

Corynebacterium diphtheria has a cell membrane which is rich in a lipid murein layer. In the exterior surface of the bacteria, pili are present. On the surface of the cell wall, a heat-sensitive protein is present, which is called antigen K. The anti-phagocytic characteristic of this antigen K, allows the bacterium to colonize, grow, multiply and produce the exotoxin.

The exotoxin produced by Corynebacterium diphtheria is a heat-labile protein, which consists of two polypeptide fragments. The A fragment is enzymatically active, while the B fragment is only supportive in the transportation process of the A fragment inside the cell.

An enrichment medium, such as Löffler’s medium, is used to grow Corynebacterium diphtheria. Low concentrations of iron are necessary in the medium for toxin production.

  1. diphtheriae is an obligatory parasite in humans, found in the mouth, throat, nose, skin, wounds and body fluids. This bacterium can survive for more than 6 months in the membranes, but is easy destroyed by physical and chemical agents.

What is Diphtheria?

Diphtheria is a bacterial infection causes by Corinebacterium diphtheria. Usually, this infection affects young children, but it rare cases it can affect adults. It is serious infection, affecting the mucous of the nose and throat, causing sore threat, high fever, difficulties in swallowing and breathing, swollen glands and weakness. The most characteristic sign for this bacterial infection is the sheet that covers the back of the throat. This sheet is sick and gray in color.  Even with good treatment, diphtheria can be fatal. Today, it is a very rare bacterial infection due to a good vaccination program. Corynebacterium diphtheria spreads in three ways:

  • Airborne droplets – with sneeze or cough the infected person releases a mist of contaminated droplets. People who might be near the infected person may inhale Corynebacterium diphtheria.
  • Contaminated personal items – drinking from the same glass, wearing the same close, handling an infected person’s used tissue, etc.
  • Contaminated household items – rarely the infection could be spread from using the same towels, toys, etc.

The disease could spread also by touching an infected wound, in case of cutaneous diphtheria.

People who are at a greater risk of getting infected include the once who don’t have a good immunization, who live in crowded places, in unsanitary conditions, travellers to an endemic area with diphtheria.

Diphtheria is very rare in industrial countries, but still common in developing countries where the immunization rates are low.


Diphtheria signs and symptoms

The incubation period is usually 2-5 days, but sometimes it can be longer. Signs and symptoms include: a thick, gray membrane that covers the back of the throat, sore throat, enlarged lymphatic glands of the neck, difficulties swallowing and breathing, fever, chills, weakness, nasal discharge, etc.

In some cases signs and symptoms can be very mild. There is also the possibility of being a carrier of the bacteria, without being aware that you are infected. Carriers of Corynebacterium diphtheria, spread the disease, without being sick themselves.

There is also cutaneous diphtheria, which affects the skin. A bacterial skin infection is accompained with redness, swallowing of the infected sight, pain, etc. This type of diphtheria is more common among people who live in poor hygienic conditions and in crowded places. An ulcer with a gray membrane may also develop in some cases.

Diphtheria could cause some serious complications, without a treatment. These complications include: breathing problems due to the membrane in the back of the throat, which obstructs the breathing. The toxins produced by diphtheria may spread with bloodstream to other organs and tissues of the human body. This can lead to heart damage, if the heart gets infected. Myocarditis (inflammation of the heart muscle) will lead to heart failure and sudden death. If the nervous system is affected by the toxins produced from diphtheria, neural damage will occur.

How is Diphtheria diagnosed?

Diphtheria is suspected in young children who complain from sore throat. If a gray, thick membrane is seen in the back of the throat, which covers the tonsils, the diagnosis is pretty clear. A material is usually taken for laboratory examination, where diphtheria is cultivated. Special media are needed for Corynebacterium diphtheria cultures to grow. In the case of cutaneous diphtheria a sample tissue from the wound is taken and tested in laboratories for Corynebacterium diphtheria.

How is Diphtheria treated?

If diphtheria is suspected, treatment should be started immediately, even without waiting for laboratory results. It is a serious bacterial infection, so there is no time to lose. An antitoxin is injected into a muscle or vein to neutralize the toxin produced by this bacterium. Penicillin or in case of allergy Erythromycin are used to treat Diphtheria. Antibiotics help kill the bacteria that have entered the organism and shorts the period of the disease by few days. Treatment requires an intensive care unit and in an isolated area, because this disease is very contagious.

How is Diphtheria prevented?

If you have been in contact with an infected person, diagnoses and antibiotic therapy are needed to prevent develop the infection. Diphtheria carriers should also be treated with antibiotics, to prevent the spread of the infection.

This disease is today very good prevented through immunization. The diphtheria vaccine is usually combined with vaccines for tetanus and pertussis, also known as the DTP vaccine. Vaccination consists of a series of five shots, typically administered in the arm or thigh, given to children at these ages:

  • 2 months
  • 4 months
  • 6 months
  • 12 to 18 months
  • 4 to 6 years.

Booster shots of the vaccine against diphtheria are needed, the first one by the age of 12, and later with a 10 year interval.