Corynebacterium diphtheria is a human pathogen and the bacteria responsible for the illness diphtheria. Diphtheria is an upper respiratory infection with symptoms usually including sore throat, fever, and swollen tonsils and pharynx. In the not so distant past, this illness was incredibly common because of it is highly contagious. Today, however, most modernized societies have access to vaccinations to prevent its spread. Because the illness is still common in some parts of the world, the medical community still often recommends vaccine boosters to those that commonly travel overseas.
The bacteria Corynebacterium diphtheria was first discovered by microbiologists Edwin Klebs and Freidrich Loffler in 1884, and have since been reclassified into four separate subspecies, although all four maintain similar properties and have the ability to cause diphtheria in humans. Whether or not a specific strain is toxic is determined by the presence of specific genes in the strain’s chromosomes.
Corynebacterium diphtheria is a gram positive bacteria, meaning a strain will retain a dark blue or purple coloration when subjected to Gram staining. This method of staining essentially further divides species of bacteria into two smaller groups; Gram-positive species and Gram negative species. This division is based on the particular properties of their cell walls. A positive test result like the one for Corynebacterium diphtheria is indicative of the presence of Peptidoglycan, a combination of sugars and amino acids, in the cell wall of the bacteria. This strain of bacteria is also pleomorphic, meaning it retains no consistent cell organization along a broad scale.
In order to determine whether or not a particular strain can produce the toxins responsible for the cause of diphtheria in humans, Elek’s test can be performed. This test is a virulence test specifically developed for determining toxigenicity of Corynebacterium diphtheria. In high concentrations of iron, toxin production is repressed when the iron binds with an aporepressor in the bacterium. However, production of the toxin is possible when iron concentrations in the medium are lower.
Luckily, this strain of bacteria is rather sensitive to many antibiotics. Antibiotics have quite possibly been one of the most beneficial advancements in modern medicine by providing affective treatment for bacterial infections such as diphtheria. While in the past diphtheria infection was often fatal, with advancements of modern medicine this is rarely the case today. Antibiotics such as penicillin, ampicillin, tetracyclines, and trimethoprim have all been shown to be quite effective in combating Corynebacterium diphtheria.