Corynebacterium diphtheria, a nonmotile Gram-positive bacillus, causes nasopharyngeal and cutaneous diphtheria in humans. In children, the most common site of infection is the upper respiratory tract mucosa. The major hallmark of pharyngeal diphtheria is the pseudomembrane, due to the production of toxin. The toxin can also cause nerve damage, myocarditis and cervical lymph nodes swelling, resulting in life-threating systemic complications. Cutaneous diphtheria produces impetigo-like lesions (Medical Microbiology).
Innate immune system is recruited when C. diphtheria establishes infections. Neutrophils and macrophages recognize bacteria through the common molecular patterns on bacteria. C. diphtheria cells are engulfed and killed in the phagolysomes.