Snapshot A 23-year-old man presents to a travel clinic in preparation for his trip to Yemen. He reports that his last Tdap vaccine was at age 11 and he has not received any vaccinations since then. Noting especially that diphtheria outbreaks have been documented in Yemen, his physician recommends the Td booster, which is supposed to be given at 10-year intervals. Introduction Classification Corynebacterium diphtheriae aerobic gram + rod produces diphtheria toxin transmission respiratory droplets Associated conditions diphtheria cutaneous diphtheria ulcerative lesions or cellulitis can occur independently of respiratory diphtheria Prevention DTap vaccine vaccine against diphtheria, tetanus, and pertussis 5 doses before school-age, completed by 4-6 years of age Tdap vaccine booster vaccine at 11-12 years of age should also be given to pregnant mothers and those around them Td vaccine tetanus and diphtheria toxoid vaccine at 10-year intervals Epidemiology Demographics rare in the US more common in developing countries ETIOLOGY Pathogenesis diphtheria exotoxin inactivates elongation factor (EF-2) via ADP-ribosylation inhibits protein synthesis, causing necrosis in respiratory, cardiac and central nervous system tissue affects mucous membranes, especially the respiratory tract exotoxin is encoded by β-prophage Presentation Symptoms fever sore throat malaise may have a croup-like cough Physical exam pseudomembranous pharyngitis gray or bluish white membrane seen on soft palate, tonsils, or back of the throat bleeds easily if irritated develops 2-3 days after symptoms severe cervical lymphadenopathy “bull neck” myocarditis arrhythmias Studies Bacterial culture gram + rods with blue and red granules (metachromically) seen on culture cysteine-tellurite agar (appears as black colonies) Löffler medium positive Elek test for diphtheria toxin Making the diagnosis most cases are clinically diagnosed and confirmed with a culture Differential Streptococcal pharyngitis distinguishing factor no pseudomembrane on mucous membranes Treatment Medical diphtheria antitoxin indication all patients antibiotics indications all patients drugs erythromycin penicillin G Complications Airway compromise from soft tissue swelling Heart failure from myocarditis Secondary bacterial infection (i.e., pneumonia) Prognosis Symptoms are insidious Mortality is higher in young children, but generally good with prompt treatment