Corynebacterium diphtheriae is the causative agent of diphtheria.Diphtheria bacteria are Gram-positive, pleomorphic, often club-shaped rods. The individual cells tend to group in V, Y, or palisade arrangements (see figure).Humans are the sole pathogen reservoir for diphtheria. Infection sources include infected persons and carriers (rare). The disease is usually transmitted by droplet infection, or less frequent indirectly via contaminated objects. Infected are the mucosa of tonsils, pharynx, nose and conjunctiva. Wounds and skin lesions can also be infected. The pathogens invade the host through these portals, reproduce, and produce toxin, resulting in cell damage. After an incubation period of 2-5 days the inflammatory reaction leads to collection of a grayish-white exsudate, the matrix of the 'diphtherial pseudo-membrane' consisting of fibrin, dead granulocytes, and necrotic epithelial cells. This coating adheres quite strongly to the mucosa. It may extend into the larynx, thus eventually hindering respiration. Regional lymph nodes are highly swollen.The intoxication leads to parenchymal degeneration in the cardiac muscles, liver, kidneys and adrenal glands. Motor cranial nerve paralysis. Late sequel damage due to the intoxication is frequently seen after the acute infection has subsided. Death can be caused.
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