• Corynebacterium diphtheriae is an irregular staining, pleomorphic, bacillus.
• Although they stain gram-positively with short chains in "V," "Y," or "Chinese letter" configuration, they do not have a typical gram-positive cell wall. Their cell wall contains arabinose, galactose, diaminopimelic acid, and short chain mycolic acids
• A nonmotile, facultative anaerobe (def).

Habitat

• Humans are the only known reservoir; carried in the oropharynx (def) or on the skin.

Source

• Spread person to person by contact with respiratory droplets or skin lesions.

Epidemiology

• Worldwide in unvaccinated hosts or asymptomatic carriers.
• Very rare in developed countries where children are routinely vaccinated against diphtheria.

Clinical Disease

• Respiratory diphtheria develops after a 2-6 day incubation period. Symptoms include malaise, pharyngitis, and low-grade fever. A thick pseudomembrane composed of bacteria, plasma cells (def), lymphocytes (def), fibrin, and dead cells develops and covers the tonsils, uvula (def), and palate (def); may extend down to the larynx or up into the nasopharynx. Complications in severe disease include breathing obstruction, cardiac arrhythmia (def), coma, and death.
• Cutaneous anthrax appears as a papule (def) that develops into a chronic, nonhealing ulcer (def) occasionally covered by a grayish membrane.

From Corynebacterium Infections , by Lynda A Frassetto, MD, Associate Clinical Professor, Department of Internal Medicine, University of California at San Francisco School of Medicine; and Lynda A Frassetto, MD, is a member of the following medical societies: American College of Physicians, and American Society of Nephrology.