Clinical bacterial disease - Diphtheria (symptoms, transmission, toxigenicity, mechanism, diagnosis, treatment, prevention).

1. DIPHTHERIA
Submitted to :
Dr. Isha Kohli
Submitted by :
Himani Bhushan
M.Sc (Microbiology)
2018-20

2. Corynebacterium diphtheriae
• It is a non-motile, non-encapsulated, non-
sporulating gram positive rod shaped
bacterium.
• They have club shaped ends and displays a
characteristic v- shaped morphology.
• It is the leading causing agent of Diphtheria.
• It is a contagious and potentially life
threatening bacterial disease that usually
affects the mucous membranes of the nose &
throat.

3. • The fatality rate ranges from 5-10%.
• Diphtheria can lead to breathing problems,
heart failure, paralysis & sometimes death.
• The infection is caused due to an exotoxin.
• The toxin was isolated in 1888.

4. • Symptoms appears after 2-5 days of infection.
• Some people don’t experience any symptoms
while others have mild symptoms similar to
those of common cold.
• Thick grey coating on throat & tonsils is most
common symptom.

5. • Additional symptoms includes :
1. Difficulty in breathing or swallowing
2. Changes in vision
3. Slurred speech
4. Signs of shock (pale & cold skin) & rapid
heartbeat
• Poor hygiene and living in tropical area might
cause ‘Cutaneous diphtheria’ i.e. ulcers and
redness in the affected area.

6. TRANSMISSION
Contact with infected
individual
Contact with objects
having bacteria

7. • Two factors influence the production of diphtheria
toxin :-
1. Low extracellular concentration of iron.
2. Presence of lysogenic prophage in the bacterial
chromosome.
• The gene for toxin production (tox gene) occurs
on the chromosome of the prophage while a
bacterial repressor protein controls the regulation
of this gene.
• The repressor is activated by iron.
• High yield of toxin is synthesized by bacteria
under iron deficiency conditions.
Toxigenicity

8. • Only the strains lysogenized by the beta phage
produce diphtheria toxin.
• Whereas a phage lytic cycle is not necessary
for the toxin production and release.
• Though the tox gene is not part of bacterial
chromosome, the regulation of toxin
production is under bacterial control since the
DtxR (regulatory) gene is on the bacterial
chromosome and toxin production depends on
bacterial iron metabolism.

9. •Diphtheria toxin is
a two component
bacterial exotoxin
synthesized as a
single polypeptide
chain.
•It contains two
domains viz A
(Active) & B
(binding) domain.
•B chain contains T
(translocation)
region.

10. MECHANISM

11. DIAGNOSIS
• Physical examination to check for swollen
lymph node.
• Histopathologic diagnosis
• Throat culture

12. TREATMENT
Antitoxin Injection
Antibiotics (Penicillin,
Erythromycin,
Clindamycin,
Rifampicin)

13. PREVENTION
• By vaccine called DTaP.
• Its usually given in a single shot.
• It helps children younger than age 7 develop
immunity to diphtheria, tetanus and pertussis.
• Tdap is a booster immunization given at age
11 that offers continued protection from these
diseases for adolescents and adults.

14. THANK YOU