Corynebacterium diphtheriae

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2. Corynebacterium diphtheriae

3. Morphology Corynebacterium
diphtheriae
1. C.diphtheriae is club shaped
gram positive bacilli that typically
shows two characteristic features:
a. Chinese letter arrangement or cuneiform arrangement
b. Metachromatic granules

4. Morphology Corynebacterium
diphtheriae
Chinese letter arrangement
They appear as V or L-shaped in smear, which
is due to the bacterial cells divide horizontally
and daughter cells tend to lie at acute angle
to each other. This type of cell division is
called snapping type of division.

5. Morphology Corynebacterium
diphtheriae
Metachromatic granules
a. Present poles of bacilli
b. Also called as polar bacilli/volutin granules
c. Storage granules
d. Granules are stained strongly gram-positive compared
to remaining part of bacilli.

6. Morphology Corynebacterium
diphtheriae
•Gram-positive bacilli
•Club shaped swellings at the
poles
•Nonmotile
•Non-spore-forming

7. Virulence factors: Corynebacterium
diphtheriae
Diphtheria Toxin (DT) is the primary virulence factor responsible for diphtheria
• Toxin has Two fragments:
A B
Active Binding
• Fragment A helps in entry
• Fragment B is the binding fragment which binds to host receptor
Diphtheria Toxin:

8. Virulence factors: Corynebacterium
diphtheriae
Diphtheria Toxin:
Factors regulating Toxin production:
• Phage coded: DT toxin has β-Corynephage, carrying tox gene
• Iron concentration
• DT repressor
• Biotypes: 3 biotypes

9. Clinical manifestation: Corynebacterium
diphtheriae
•Respiratory Diphtheria
•Cutaneous Diphtheria
•Systemic Diphtheria

10. Clinical manifestation: Corynebacterium
diphtheriae
Respiratory Diphtheria
Site: Tonsil, Pharynx, nose, larynx
• Faucial Diphtheria
• Extension of pseudomembranous
• Bull neck appearance
Incubation period: 3-4 days

11. Clinical manifestation: Corynebacterium
diphtheriae
Cutaneous Diphtheria
Site: Skin
• Not Toxin-mediated
• Punched out ulcerative lesions
• Necrosis

12. Clinical manifestation: Corynebacterium
diphtheriae
Systemic Diphtheria
• Neurologic manifestations: Toxin mediated
• Myocarditis

13. Pathogenesis: Corynebacterium
diphtheriae
Pathogenesis of diphtheria is toxin mediated-
• Diphtheria is toxemia.
• Bacilli are non-invasive, secrete the toxins which spreads by
bloodstream to various organs.
• Toxin is responsible for all type of manifestations including local
(Respiratory) and systematic complications.

14. Laboratory Diagnosis: Corynebacterium
diphtheriae
Specimen: Throat swab or the portion of membrane
Direct smear:
Albert stain Gram stain
Club shaped gram-positive bacilli with
Chinese letter arrangement
Green bacilli with bluish black
metachromatic granules

15. Laboratory Diagnosis: Corynebacterium
diphtheriae
Culture:
Enriched Media: Blood agar, Chocolate agar and Loeffler’s serum slope.
Selective medium: Potassium tellurite agar, Tindale medium
Biochemical identification:
Hiss serum sugar media: Ferments Glucose, maltose and starch
Urease test Negative

16. Laboratory Diagnosis: Corynebacterium
diphtheriae
Diphtheria Toxin Demonstration:
In vitro:
Elek’s gel precipitation test
Detection of tox gene by PCR
Detection of toxin by ELISA
In vivo test::
Subcutaneous
Intracutaneous test

17. Treatment: Corynebacterium
diphtheriae
 Antitoxin
 Antibiotics: Penicillin or Erythromycin

18. Prophylaxis: Corynebacterium
diphtheriae
Active immunization is done with diphtheria toxoid as it induces antitoxin production in body
Types:
Single vaccine: Diphtheriae toxoid
Combined Vaccine

19. Prophylaxis: Corynebacterium
diphtheriae
DPT VACCINE: Diphtheria toxoid, Pertussis (whole cell), Tetanus toxoid
Introduction
 Infants are immunized simultaneously
against three important childhood
diseases.
 Pertussis component act as adjuvant
and increases immunogenicity of DT
and TT.

20. Prophylaxis: Corynebacterium
diphtheriae
DPT VACCINE: Diphtheria toxoid, Pertussis (whole cell), Tetanus toxoid
Types : Diphtheria are prepared by two methods
1.Plain formol toxoid: (FLUID TOXOID): Prepared by incubating
toxoid with formalin
2.Absorbed (ALUM ABSORDED): Formol toxoid is absorbed to to
alum acts as adjuvant and increases the immunogenicity of toxoid.

21. Prophylaxis: Corynebacterium
diphtheriae
DPT VACCINE: Diphtheria toxoid, Pertussis (whole cell), Tetanus toxoid
Administration of DPT:
• DPT is scheduled under national immunization schedule in
India
• Total five dose are given; 3 dose at 6,10,14 weeks
followed by two booster dose at 16-24 month and 5 years
SITE: Intramuscularly
Protective titer: ≥0.01 unit/ml

22. Prophylaxis: Corynebacterium
diphtheriae
DPT VACCINE: Diphtheria toxoid, Pertussis (whole cell), Tetanus toxoid
Adverse reactions:
•Mild: fever
•Severe: Neurological complications