Respiratory infection bacteria-Corynebacterium diphtheriae

Corynebacterium diphtheriae (Corynebacterium. Diphtheriae)

1. Biological traits

1. Morphology and staining

G + bacillus, non-capsular, flagella, spores, meta-stained granules showing metachromatic particles

2. Cultural characteristics and biochemical reactions

(1) Cultivation:

Culture medium: Lu's medium Temperature: 34-37 ℃ Aerobic or facultative anaerobic

Colonies: off-white, smooth, moist small colonies

(2) Biochemical reaction

Potassium tellurite → Tellurium

1. Variation: morphology, colony, virulence, and lysogen conversion

2. resistance

(1) Anti-drying and sunlight

(2) Sensitive to damp heat, disinfectant

(3) Sensitive to penicillin and erythromycin

2. Pathogenicity and immunity

(1) Pathogenic substances

1. Diphtheria toxin (diphtherotoxin)

(1) Toxic production process:

β-Corynebacterium phage invades non-toxic Corynebacterium diphtheria → tox gene integration with host chromosome → lysogeny conversion diphtheria toxin production

(2) Toxin substances

â‘  Strong toxicity and strong antigenicity

â‘¡ It is composed of two peptide chains A and B, A chain is a toxic functional region, and B chain is a binding translocation region

â‘¢ Mechanism of action:

The B-chain receptor binding region binds to cell surface receptors → the translocation region assists the A chain to enter the cell → catalyzes the inactivation of the binding of EF-2 to ADPR → inhibits protein synthesis

2. Cord factor: glycolipid, destroys animal cell mitochondria

3. K antigen: glycoprotein, anti-phagocytosis

(2) Diseases caused by: diphtheria

(3) Immunity: mainly depends on the neutralization of antitoxin

(4) Sikh test:

Concept: A test to investigate whether a population has immunity to diphtheria. The principle is the neutralization of endotoxin and antitoxin.

1. Microbiological examination

1. Specimen: Nasopharyngeal Swab

2. Smear staining microscopy: preliminary diagnosis

3. Separate culture: Lu's serum slope

4. Identification:

(1) Biochemical reaction

(2) Toxicity experiment

â‘  In vivo method: guinea pig

â‘¡ In vitro method: agar Elek plate toxicity test

2. Prevention Principles

1. Artificial active immunization: Baibaibo triple vaccine

2. Artificial passive immunity: injection of diphtheria antitoxin

3. Antibacterial treatment: penicillin, erythromycin

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