Corynebacterium diphtheriae is an aerobic and facultative anaerobic organism but grows best under aerobic conditions. C.
diphtheriae is non-spore-forming and non-motile gram-positive but usually stains unevenly and weakly.
They lack of motility is especially useful for differentiating them from Listeria. It grows at 37° C and at pH of 7.2 – 7.4 on media enriched with blood serum, or egg. C.
diphtheriae, the causative agent of diphtheria, is usually found in the upper respiratory tract, on the skin, conjunctiva and vagina.
Its capacity to produce toxin and the immunity state of the individual decide whether diphtheria will evolve. At the site of entry it produces a greyish false membrane – constituted of a fibrinoleukocytic exudates. From the false membrane, where diphtheria bacilli are isolated they produce an exotoxin, which invades the tissues by the blood stream.
C.
diphtheriae ferments many sugars (glucose, galactose, maltose and dextrin). The bacteria do not ferment lactose, mannitol and sucrose. Some strains of virulent C.
diphtheriae ferment sucrose.
Characteristics of the Corynebacterium diphtheriae
