Corynebacterium diphtheriae

1
Corynebacterium diphtheriae

2
Biological Features

• Aerobic, Gram, Noncapsulated, rods
• Gray-black colonies on tellurite????medium
• Metachromatic granules

3
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

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
(No Transcript)
7
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

8
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.

9
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

10
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.

11
Prospect
tumors !!

• For therapy of

tumor
Ab
DT