Pneumonia is an inflammation of lung parenchyma characterized by exudate accumulation in alveolar spaces. It is classified clinically (community-acquired, hospital-acquired, aspiration, etc.), morphologically (lobar, bronchopneumonia, interstitial), and etiologically (bacterial, viral, fungal, etc.). Typical presentations often involve sudden onset of fever and cough, while atypical presentations may manifest as low-grade fever and dry cough without consolidation.

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Pneumonia
Inflammation of the lung parenchyma with
accumulation of exudate , inflammatory cells
and fibrin within the alveolar spaces or within
alveolar septa.
It is characterized by:
Consolidation of the affected part of the lung
Consolidation= replacement of airspaces by
inflammatory exudates giving the affected area
a firm (solid) consistency.

2. Spr 09 22
Classification of pneumonias
Three Types of Classification of
pneumonias
1.Clinical
2.Morphological (distribution of
inflammatory foci)
3.Etiological

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Clinical classification
1. Community acquired pneumonia: acquired outside
the hospital
1. Typical
2. Atypical
2. Hospital acquired (nosocomial): represents an
infection caused by organisms in the hospital
environment
3. Aspiration pneumonia
4. Necrotizing pneumonia and Lung abscess
5. Pneumonia in immunocompromised hosts
6. Chronic pneumonias

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Morphological classification
 Depending upon the site and extent of involvement of
lung:
1. Lobar pneumonia:
 involvement of the whole lobe
2. Bronchopneumonia:
 Begins as acute bronchitis and spreads locally into
lungs
 Lung has patchy areas of consolidation in same or
several lobes.
 Also k/a patchy pneumonia
3. Interstitial pneumonia:
 affects the interstitium and does NOT lead to
consolidation (syn.=atypical pneumonia or
pneumonitis.

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Etiological classification
Bacterial
Viral
Fungal
Parasitic
Ricketssial
Mycoplasma pneumoniae
Chlamydia

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Community Acquired Pneumonia
Can present in two ways:
1. Typical presentation
2. Atypical presentation

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Typical community acquired pneumonia
Epidemiology:
Majority caused by bacterial pathogens
Most often due to Streptococcus pneumoniae.
People at risk:
Splenic dysfunction
Congenital or acquired immunodeficiency.

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Typical community acquired Acute pneumonia
Can have two gross
patterns of anatomic
distribution:
Lobar pneumonia
Bronchopneumonia

9. Spr 09 9Fall 07 9
Typical community acquired Acute pneumonia
Lobar pneumonia
Consolidation of entire lobe or large portion of
a lobe.
Associated with
Predominantly intra-alveolar exudate.
spreads through pores of Kohn.
Bronchopneumonia
patchy areas of consolidation.
Usually bilateral
More common in Lower lobes.

10. Spr 09 10Fall 07 10
Consolidation
Of
entire lobe
Patchy areas
of
consolidation
Lobar pneumonia
Bronchopneumonia

11. Spr 09 11Fall 07 11
Typical community acquired pneumonia
Pathogenesis:
Inhalation of aerosol from an infected
patient.
Four Classical Stages lobar pneumonia:
1. Stage of Congestion
2. Stage of Red Hepatization
3. Stage of Gray Hepatizaiton
4. Stage of Resolution

12. Spr 09 12Fall 07 12
S. pneumoniae
Capillary
Type I pneumocyte
Edema
Neutrophil with bacteria
Pneumococci

13. Spr 09 13Fall 07 13
Stage of :
Congestion and
Red hepatization
Exudate rich in neutrophils

14. Spr 09 14Fall 07 14
Stage of Red Hepatization
Exudate rich in
Neutrophils
Congested capillaries

15. Spr 09 15Fall 07 15
Macrophage
Stage of :
Grey hepatization
Resolution

16. Spr 09 16Fall 07 16
Red hepatizationGray hepatization

17. Spr 09 17Fall 07 17
Typical community acquired pneumonia
Clinical findings
Sudden onset of
High fever
Cough productive of sputum [yellow-green (pus)
or rusty (bloody)].
Signs of consolidation in lungs on PE and X ray
Dullness to percussion
Increased vocal tactile fremitus
Chest X ray : first step in management***.
Radio-opaque lobe  Lobar pneumonia
Focal opacities Bronchopneumonia

18. Spr 09 18Fall 07 18
Complete
right upper lobe
consolidation
Lobar pneumonia

19. Spr 09 19Fall 07 19
Bronchopneumonia
Patchy infiltrates

20. Spr 09 20Fall 07 20
Laboratory findings
Blood:
Neutrophilic leukocytosis with left shift.
Sputum:
Gram positive lancet shaped diplococci
(pneumococci)

21. Spr 09 21Fall 07 21
Complications of lobar and bronchopneumonia
1. Development of Lung Abscess
2. Empyema (pus in the pleural cavities)
3. Bacteremia and sepsis with infection of other
organs.
1. Meningitis
2. Bacterial endocarditis
3. Arthritis
4. Otitis media

22. Spr 09 22Fall 07 22
Summary of other Community
acquired Acute pneumonias

23. Spr 09 23Fall 07 23
Staph aureus: (gram +ve coccus)
MC pathogen causing pneumonia following
influenza infection.
Common cause of pneumonia in IVDA
Common in nosocomial pneumonia as well
Complications: lung abscess , endocarditis or
brain/kidney abscess.
Yellow colored sputum
H.influenzae: (gram –ve rod)
MCC of acute exacerbation of COPD.
Acute epiglottitis in children.

24. Spr 09 24Fall 07 24
Pseudomonas aeruginosa: Gram –ve rod
Water loving bacteria, transmitted by
respirators
Common cause of nosocomial pneumonia and
MCC of pneumonia in CF patients.
MC pneumonia in ICU/CCU (due to respirators)
Green colored sputum (pyocyanin)
Klebsiella pneumoniae: Gram –ve rod with capsule
Causes pneumonia in alcoholics
MC pneumonia in nursing homes
Sputum: thick,gelatinous,mucoid and blood
tinged.
Involves upper lobes and cavitates like TB.

25. Spr 09 25Fall 07 25
Morexella Catarrhalis:
Common cause of pneumonia in elderly
Common cause of otitis media in children
Legionella pneumophilia (Gram –ve, need IF or
Dieterle silver stain)
Water loving bacteria (May spread via water
coolers)
Organ transplant recipients are at risk.
Pneumonia with dry cough, malaise, flu like
symptoms and striking fever.
Other findings: arthralgias, renal and CNS
findings.
Can produce hyponatremia due to interstitial
nephritis.

26. Spr 09 26Fall 07 26
Community acquired atypical
pneumonias

27. Spr 09 27Fall 07 27
Atypical community acquired pneumonia
Etiology:
Usually caused by Mycoplasma pneumoniae***
Other organisms include:
Chlamydia trachomatis (newborns)
Chlamydia pneumoniae
Viruses
Influenza virus types A and B (adults)
Parainfluenza virus (children)
RSV and SARS virus
Adenovirus (military recruits)
Coxiella burnetti (Q fever)

28. Spr 09 28Fall 07 28
Community acquired atypical pneumonias
Mycoplasma pneumoniae:
MCC of primary atypical pneumonia.
Usually involves school age children and young
adults.
Occurs in crowded conditions
Schools, prisons and military barracks.
• Pathogenesis:
Contracted by inhalation (droplet infection)

29. Spr 09 29Fall 07 29
Pathology:
Interstitial inflammatory reaction, localized
within the wall of alveoli.
Mononuclear cell infiltrate composed of
lymphocytes, histiocytes and plasma cells.
Alveolar spaces free of exudate (no
consolidation).
Community acquired atypical pneumonias

30. Spr 09 30Fall 07 30
Lymphoplasmacytic
Infiltrate in the
Alveolar septa

31. Spr 09 31Fall 07 31
Typical
Vs
Atypical pneumonia

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Atypical community acquired pneumonia
Clinical findings:
Gradual onset
Low grade fever
Non to mildly productive cough (dry cough)
No signs of consolidation (interstitial
pneumonia)
Flu like symptoms:
Headache, myalgias, pharyngitis, laryngitis
etc.
Chest X ray: minimal signs

33. Spr 09 33Fall 07 33
Other organisms causing atypical
pneumonia

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Respiratory syncytial virus (RSV):
MCC of interstitial pneumonia and bronchiolitis
in infants
Influenza virus:
Type A: produces pandemics and epidemics
Type B: epidemics
Hemagglutinins: bind virus to cell receptors in
nasal passage
Neuraminidase: dissolves mucus and facilitates
release of viral particles from infected cells.
Mild cold to bronchitis to severe pneumonia.
Superimposed bacterial infection : S.aureus

35. Spr 09 35Fall 07 35
Chlamydia psittaci:
Psittacosis is a zoonosis
Inhalation of C.psittaci from psittacine birds
(parrots, parakeets).
Primarily results in interstitial pneumonia.
Chlamydia pneumoniae:
Droplet infection
5 % of community acquired atypical
pneumonias
Relationship with coronary artery disease.
Chlamydia trachomatis:
Newborn pneumonia (infected birth canal)
Presents with staccato cough, conjunctivitis,
tachypnea.
Afebrile and eosinophilia.

36. Spr 09 36Fall 07 36
Coxiella burnetii
Only rickettsia transmitted without a
vector.
Inhalation
People at risk: dairy farmers,
veterinarians.
Sudden onset of high fever, headache,
interstitial pneumonia.