Pathogenesis of
Pneumonia
19. NURIN NADIAH YUSRI
Types of Pneumonia
Settings
Etiology
Bacteria
Community-Acquired
Pneumonia (CAP)
outside of a hospital in a
community setting.
Viral
Others (Fungal)
Hospital-Acquired
Pneumonia (HAP)
48 hours after being admitted in
an inpatient setting.
Ventilator Associated
Pneumonia (VAP)
48 hours after endotracheal
intubation
Pattern
Bronchopneumonia
Lobar pneumonia
2 types of acute bacterial pneumonias
Bronchopneumonia
1
●
An acute bacterial infection of terminal bronchioles that extends
into the surrounding alveoli resulting in patchy consolidation of the
lung
Lobar pneumonia
●
An acute bacterial infection of a part of a lobe, the entire lobe, or
even two lobes of one or both the lungs
2
1) Bronchopneumonia
●
Also known as Lobular
Pneumonia
●
Frequent at the extreme of life
(infancy and old age)
●
Very rarely, severe forms of
pneumonia
●
may results in the formation of
lung abscess, a complete
breakdown of tissue and
formation of pus-filled pockets in
focal areas of the lung.
•
Most commonly, bilateral and involve
lower zone of lungs due to gravitation of
the secretion
Histologically,
• Acute bronchitis
•
Suppurative exudate, chiefly neutrophils
•
Thickening of alveolar septa by
congested capillaries
•
Less involved alveoli containing aedema
fluid
2) Lobar Pneumonia
●
Divided based on etiologic
microbial agent :
●
●
●
●
Pneumococcal Pneumonia
Staphylococcal pneumonia
Streptococcal pneumonia
Pneumonia by gram-negative
aerobic bacteria
●
Can spread via communityacquired infection,
hematogenous spread of
infection
Lobar pneumonia : 4 phase
1
Initial phase : Stage of
Congestion
2
Early Consolidation :
Red Hepatisation
3
Late Consolidation :
Grey Hepatisation
4
Resolution
Stage of Congestion
1-2 days
●
Dilatation and congestion
of the capillaries in the
alveolar walls
●
Pale eosinophilic oedema
fluid in the air spaces
●
A few red cells and
neutrophils in the intraalveolar fluid
●
Numerous bacteria
Red Hepatisation
2-4 days
•
Oedema fluid of preceding
stage is replaced by strands of
fibrin
•
Marked cellular exudate of
neutrophils and extravasation
of red cell
•
Many neutrophil shows
ingested bacteria
Grey Hepatisation
4-8 days
•
•
The fibrin strands are
dense and more
numerous
The cellular exudate of
neutrophils is reduced
due to disintegration of
many inflammatory
cells
Resolution (1-3 weeks)
●
Previously solid fibrinous
constituent is liquified by
enzymatic action
●
Normal aeration in affected lobe
is restored
●
Macrophages are predominant
cells in the alveolar spaces,
while neutrophils diminished
●
Alveolar capillaries are engorged
●
Progressive removal of fluid
content from air spaces
Trigger
Thanks
REFERENCES
Harsh Mohan, Textbook of Pathology Sixth Edition
Robbins and Cotrans Pathologic Basic of Disease, 9th
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