In this ppt, discussing about pathogenesis of Corynebacterium diphtheriae and Mycobacterium tuberculosis and also included other types of lower respiratory tract infections causing microorganisms.

1. PREPARED BY
ARPITA CHANDRA
Medical Microbiology

2. Pathogenesis of the respiratory tract
 Microorganism primarily cause disease by a limited
number of pathogenic mechanism
 An organism is successful in establishing an infection
is dependent not only on the organism’s ability to
cause disease but also on the human host’s ability to
prevent the infection.

3. Host factors
 Non specifically protect the respiratory tract from
infection:
- Nasal hairs
- Convoluted passage
- Mucous lining of the nasal turbinates
- Secretory IgA and
- lysozymes
- Cilia and mucous lining of the trachea
- Reflexes ( coughing & sneezing)

4. Microorganism factors
 Adherence- By proteinaceous finger like surface
structures called Fimbriae.
Streptococcus pyogens
– Specific adherence factors Lipoteichoic acids and certain
proteins (M protein)
Other bacteria
Staphylococcus aureus
Enterobacteriaceae
Legionella spp
Pseudomonas
Bordetella pertusis and
Haemophilus spp

5. Toxins
Once the organism colonizes
respiratory epithelium
It produces a toxins
That can lead to respiratory distress

6.  Corynebacterium diphtheriae
causes – Necrosis and sloughing of the epithelial
mucosa producing a “diphtheritic (pseudo) membrane”
It extend from
Anterior nasal mucosa to the bronchi
Membrane may cause sore throat
Iterfere with respiration and swallowing

7. Toxin similar to diphtheria toxin
1. Pseudomonas aeruginosa
2. Bordetella pertussis
Staphylococcus aureus and beta hemolytic streptococci
Produces
Extracellular enzymes
Damage host cells
(Tissue nectrosis and destruction of phagocytic cells)

8. Mycobacterium Tuberculosis
 Classic representative of Intracellular pathogens
Droplet nucleus (few tubercle bacilli)
carried to an alveolus
Slowly multiply with in alveolar macrophages
MTB destroys the macrophages
Granuloma formation

9. Disease of the lower respiratory tract
BRONCHITIS- Cough, Variable fever and excess sputum
production
ACUTE CHRONIC
Mainly caused by Viral
agents- Inflenza virus,
adenovirus, rhinovirus,
corornavirus and RSV
Bacteria – B. pertussis,
Mycoplasm pneumoniae,
Chlamydophila
pneumoniae
Affecting about 10% to 25% of
adults
Clinical symptoms- Excessive
mucous production , coughing
at least 3 consecutive months
for more than 2 successive years
Bacteria- H. influenzae, S.
pneumoniae and Moraxella
catarrhalis

10. THANK YOU