Corynebacterium diphtheriae is a gram-positive, rod-shaped bacterium that is classified in the phylum Actinobacteria and the family Corynebacteriaceae. It is a pathogen, meaning that it can cause disease in humans and animals.
Corynebacterium diphtheriae is further classified into different biotypes based on its ability to produce certain toxins and enzymes. The most common biotypes of C. diphtheriae are gravis, intermedius, and mitis.
morphological characteristics of Corynebacterium diphtheriae
Corynebacterium diphtheriae is a gram-positive, rod-shaped bacterium that is typically found in the respiratory tract of humans and animals.
C. diphtheriae is typically 0.6-0.9 µm in diameter and 1.5-5 µm in length. It has a characteristic “club-shaped” appearance, with rounded ends and a slightly swollen middle section. The bacterium is non-motile, meaning that it does not have the ability to move on its own.
colony characteristics of the Corynebacterium diphtheriae
Corynebacterium diphtheriae typically grows on solid media as circular, raised colonies that are 1-2 millimeters in diameter. The colonies may be smooth or rough in texture, depending on the specific biotype of the bacterium.
On blood agar plates, C. diphtheriae colonies typically appear as small, gray, opaque, and moist. They may have a slightly yellow or greenish tinge, and they may produce a characteristic “ground glass” appearance due to the presence of the bacterial toxin.
C. diphtheriae is a slow-growing bacterium, taking 3-5 days to form colonies on solid media. It is also a facultative anaerobe, meaning that it can grow in the presence or absence of oxygen. However, it grows best in an aerobic environment with 5-10% carbon dioxide.
biochemical test for the detection of Corynebacterium diphtheriae
There are several biochemical tests that can be used to detect Corynebacterium diphtheriae, a bacterium that can cause a serious and potentially life-threatening infection called diphtheria. These tests are typically performed on cultures of the bacterium that have been grown in the laboratory from specimens collected from an infected individual.
One common test for the detection of C. diphtheriae is the production of a characteristic toxin. C. diphtheriae produces a potent exotoxin that is responsible for the clinical signs and symptoms of diphtheria. This toxin can be detected using a variety of methods, including the Elek test, which is based on the ability of the toxin to precipitate with rabbit serum.
Another common test for the detection of C. diphtheriae is the production of a specific enzyme called catalase. C. diphtheriae is a facultative anaerobe, meaning that it can grow in the presence or absence of oxygen.
However, it produces catalase, an enzyme that breaks down hydrogen peroxide, which is a product of oxygen metabolism.
The production of catalase can be detected using a simple test in which a drop of 3% hydrogen peroxide is added to a culture of the bacterium. If catalase is present, the hydrogen peroxide will be broken down, resulting in the release of oxygen bubbles.
Other biochemical tests that may be used to detect C. diphtheriae include tests for the production of certain enzymes and metabolic pathways, such as the ability to ferment glucose or other sugars. These tests can help to confirm the identification of C. diphtheriae and differentiate it from other bacterial species.