Corynebacterium

Corynebacteria
The genus Corynebacterium includes Corynebacterium diphtheriae, the cause of the prototypic toxin-mediated disease diphtheria, as well as several usually harmless human commensals. Corynebacteria are small, slender, pleomorphic, Gram-positive rods of distinctive morphology that tend to stain unevenly. Corynebacteria characteristically, they possess irregular swellings at one end (often near the poles) that give them the "club-shaped" appearance. Irregularly distributed within the rod the granules staining deeply with aniline dyes (metachromatic granules) that give the rod a beaded appearance. Individual corynebacteria in stained smears tend to lie parallel or at acute angles to one another. True branching is rarely observed in cultures .They are nonmotile, unencapsulated, and do not form spores. Corynebacterium is a large genus of diverse habitat. Most species are facultative anaerobes, and those found associated with humans, including the pathogen C.diphtheriae, grow aerobically on standard laboratory media such as blood agar.
A. Corynebacterium diphtheriae
Diphtheria, caused by C. diphtheriae, is an acute respiratory or cutaneous disease and may be a life-threatening illness. The development of effective vaccination protocols and widespread immunization beginning in early childhood has made the disease rare in developed countries. However, diphtheria is a serious disease throughout the world, particularly in those countries where the population has not been immunized.