上海交通大学：《医学微生物》课程教学资源（PPT课件讲稿）英文版 Corynebacterium diphtheriae

Corynebacterium diphtheriae

Corynebacterium diphtheriae

Biological Features o Aerobic, Gram*, Noncapsulated, rods ●Gray- black colonies on tellurite亚碲酸盐 medium Metachromatic granules Chinese-letter morphology in Gram stain

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

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

Transmission and Risk factors ⚫ 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

Pathogenesis of diphtheria 3, Disease Pharyngeal diphtheria 4. Exit oxia-pseudomembrane obstruction Lymphadenitis rarely become Cutaneous diphtheria disseminated but Systemic complications toxin becomes blood borne Toxic myocarditis and congestive heart failure o Early stages: Sore throat. Low fever. Swollen neck glands Late stages: Airway obstruction and breathing difficulty. shock

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

Diphtheria Toxin (DT e Cleaved to yield A/B fragment, joined by S-s bond A(catalytic domain) B(transmembrane and receptor binding domains o Receptor: heparin-binding epidermal growth factor -rich on cardiac cells and nerve cells o Toxin diffuses throughout body via blood Cardiac, neurologic complications Heart/respiratory damage, paralysis NH3+ =5 Coated pit 1pH5. Endosome Receptor surface 灯可r Result: Protein synthesis inhibition and cell death AD++ EF-2 ADPR-EF-2+ nicotin

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

● Thick grey pseudomembrane composed of fibrin epithelial cells, bacteria and 10 y/o boy with polymorp severe diphtheria neutrophils .conjunctivitis e Pseudomembrane ● pharyngeal membrane may cause blockage, ◆ bull neck suffocation ◆ severe myocarditis e all vaccines contraindicated CDC The cervical lymph nodes enlarge causing oedema of the neck(a classical condition of bullneck) Epidemiology e Largely controlled now by vaccination e However, factors such as poverty and other social factors have led to diphtheria being an endemic/epidemic in many regions of the orld

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

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 ⚫ Toxoid introduced in 1923, now widely used

Schicke test o 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 试验侧 对照侧 本质 阴性反应 有免疫力 阳性反应24~48h 无免疫力 4~7d达峰 假阳性反应618h红肿 同前 有免疫力,超敏反 1~2d消退 混合反应6~18h红肿 6~18h红肿无免疫力,超敏反应 4~7d达峰 3~4d反应消退

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

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

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

Control Sanitary: Reduce carrier rate by use of vaccine o 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

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