Corynebacterium diphtheriae
Corynebacterium diphtheriae
Biological
Biological
Features
Features
Aerobic, Gram+, Noncapsulated, rods
Gray-black colonies on tellurite 亚碲酸盐 medium Metachromatic granules
Transmission and
Transmission and
Risk fact
Risk fact
ors
ors
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
Pathogenesis of diphtheria
Pathogenesis of diphtheria
Early stages: Sore throat. Low fever. Swollen neck glands.
Diphtheria Toxin
Diphtheria Toxin
(DT)
(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
Thick grey
‘pseudomembrane’ composed of fibrin, epithelial cells,
bacteria and polymorph neutrophils
Pseudomembrane
may cause blockage, suffocation
The cervical lymph nodes enlarge causing
The cervical lymph nodes enlarge causing oedemaoedema
of the neck (a classical condition of
of the neck (a classical condition of ‘‘bullneckbullneck’’))
Largely controlled now by vaccination However, factors such as poverty and other
social factors have led to diphtheria being an
endemic/epidemic in many regions of the world
Epidemiology
Immunity
Immunity
Immunization of animals with altered toxin, pr oducing antitoxin, was first done in 1890, 1st used in humans in 1891
Toxin-antitoxin introduced by Theobald Smit h in 1909, used little
Schick test
Schick test
Be used to ascertain population risk
This test involves the injection of a minute amount of
DIAGNOSIS
DIAGNOSIS
Clinical: Muscle weakness, edema and a pseu domembranous material in the upper respirator y tract characterizes diphtheria.
Control
Control
Sanitary: Reduce carrier rate by use of vac
cine.
Immunological: A vaccine (DPT) prepare
d from an alkaline formaldehyde inactivated t oxin (i.e. toxoid) is required. Passive immuni zation with antitoxin can be used for patients.
Chemotherapeutic: Penicillin, erythromy
Prospect
Prospect
For therapy of
Ab
DT tumor
