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Corynebacterium diphtheriae

Corynebacterium diphtheriae. Chinese-letter morphology in Gram stain. Biological Features. Aerobic, Gram + , Noncapsulated, rods Gray-black colonies on tellurite 亚碲酸盐 medium Metachromatic granules. solely among humans spread by droplets secretions direct contact. Poor nutrition

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Corynebacterium diphtheriae

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  1. Corynebacterium diphtheriae

  2. Chinese-letter morphology in Gram stain Biological Features • Aerobic, Gram+, Noncapsulated, rods • Gray-black colonies on tellurite亚碲酸盐medium • Metachromatic granules

  3. solely among humans spread by droplets secretions direct contact Poor nutrition Crowded or unsanitary living conditions Low vaccine coverage among infants and children Immunity gaps in adults Transmission and Risk factors

  4. Pathogenesis of diphtheria • Early stages:Sore throat. Low fever. Swollen neck glands. • Late stages:Airway obstruction and breathing difficulty. Shock

  5. Diphtheria Toxin (DT) • Cleaved to yield A/B fragment, joined by S-S bond- A (catalytic domain) - B (transmembrane and receptor binding domains) • Receptor: heparin-binding epidermal growth factor - rich on cardiac cells and nerve cells • Toxin diffuses throughout body via blood- Cardiac, neurologic complications - Heart/respiratory damage, paralysis

  6. Immunity • Immunization of animals with altered toxin, producing antitoxin, was first done in 1890, 1st used in humans in 1891 • Toxin-antitoxin introduced by Theobald Smith in 1909, used little • Toxoidintroduced in 1923, now widely used

  7. Schick test • Be used to ascertain population risk This test involves the injection of a minute amount of the diphtheria toxin under the skin. The absence of a reaction indicates immunity.

  8. DIAGNOSIS • Clinical: Muscle weakness, edema and a pseudomembranous material in the upper respiratory tract characterizes diphtheria. • Laboratory: Tellurite media is the agar of choice for isolation of Corynebacteria, which produce jet black colonies

  9. Control • Sanitary: Reduce carrier rate by use of vaccine. • Immunological: A vaccine (DPT) prepared from an alkaline formaldehyde inactivated toxin (i.e. toxoid) is required. Passive immunization with antitoxin can be used for patients. • Chemotherapeutic: Penicillin, erythromycin or gentamicin are drugs of choice.

  10. Prospect For therapy of tumors !! tumor Ab DT

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