Semester 3 mini 3: Pathology of Pneumonia

Pulmonary Infections: when there is an impairment of the normal PULMONARY DEFENSE MECHANISM
1. loss of cough reflex (coma, anesthesia..etc.)
2. injury to mucociliary apparatus (smoking)
3. deficiency of secretory IgA in bronchial mucus
4. decreased phagocytic/bactericidal function of alveolar macrophages (smoking, alcohol, drugs)
5. pulmonary congestion & edema (CHF, ARDS…)
6. presence of bronchial obstruction (FB, tumors)

No completely satisfactory way to classify pneumonia…? best done by causative organism
1. Acute Community Acquired
-bacterial eg. strep pneumoniae; hemophilus influenzae
-viral and mycoplasma pneumonias (atypical pneumonias)
2. Nosocomial (hospital acquired)
-eg. klebsiella, pseudomonas, staph. aureus (may be penicillin-resistant)

Chronic Pneumonias
-mycobacterium tuberculosis
-histoplasma capsulatum
-coccidioide imitis

Aspiration Pneumonias
-oral flora organisms like bacterioides or staph. aureus
-often gram negative

Immuno-compromise host
-pneumocystis jiroveci
-invasive candidiasis
-mycobacterium avium-intracelluar

Lipid pneumonia
fatty pneumonia


Routes of Infection
1. several possible routes of infection of lung exist:
2. ASPIRATION of contaminated secretions–MOST COMMON
3. INHALATION of infected airborne droplets
5. DIRECT EXTENSION of an acute inflammatory process from an adjacent organ or structure

An INCREASED RISK of bacterial infection is associated w/impairment of the defense mechanism, as in any of these clinical situations:
1. Loss of Consciousness
2. Immunodeficiency state
3. Pulmonary edema
4. Neutropenia
5. Chronic airway obstruction
6. Viral infection

Bacterial Pneumonia: Bronchopneumonia
1. =patchy exudative consolidation of lung parenchyma, caused by bacterial infection (stapylococci, streptococci, pneumococci, H. incluenzae, pseudomonas, E. coli). The lungs show:
-FOCAL AREAS OF CONSOLIDATION-composed of PNL exudate filling alveoli
2. COMPLETE RESOLUTION restores the normal lung structure, but organization of the exudate may occur->FIBROUS SCARRING. STAPHYLOCOCCI tend to cause ABSCESSES

Bacterial Pneumonia: Lobar Pneumonia
1. acute bacterial infection, with CONSOLIDATION OF WHOLE SEGMENTS or an ENTIRE LOBE of the lung, ->Pneumococci.
2. Classical Stages (untreated cases):
-Red hepatization (RBCs)
-Gray hepatization (no RBCs)

Complications (of any bacterial pneumonia):
1. abscess
2. empyema
3. organization
-fibrosis, scarring
4. pericarditis
5. bacteremia
-endocarditis, meningitis

Mycoplasmal or viral
Mycoplasmal or viral

Interstitial Pneumonia:
-Mycoplasmal (atypical pneumonia)
-severe viral or mycoplasmal infections cause inflammation of the lung parenchyma: MONO-NUCLEAR CELLULAR INFILTRATE
-Sometimes hyaline membranes may form, reflecting diffuse alveolar damage.
-Viruses cause necrosis of bronchial and alveolar epithelium
-Secondary bacterial infection is common

Other Pneumonias
1. Aspiration Pneumonia
2. Lipid Pneumonia – lung has a yellow color grossly
3. Endogenous: obstruction of bronchus by tumor
4. Exogenous: inhalation of mineral oil

Bird Flu (Avian Influenza) – Swine Flu
-H5N1 causes avian influenza
-H1N1 causes swine flu
-disease in humans: severe viral pneumonia, often followed by secondary bacterial pneumonia, and may lead to cyanosis, multi-organ failure and death.

Lung Abscess
=localized suppurative inflammation of the lung parenchyma, caused by staphylococci, mixed infections & anaerobes. predisposed to by:
1. Aspiration-commonest cause
2. Postpneumonic
3. Septic embolism
4. Obstructive bronchial tumors
5. Spread of liver abscess
6. Direct trauma
7. Rare (actinomycosis, hydatid)

Hypersensitivity Pneumonia
=immunologically mediated interstitial lung disorders, caused by inhalation of organic dust containing antigen such as thermophilic bacteriae:
1. Farmer’s lung: spores of thermoph.
2. Byssinosis: cotton, linen fibers
3. Bagassosis: thermoactinomyces saccharii growing in sugar-cane

-interstitial pneumonitis, w/ granulomas; progressing to interstitial fibrosis.
-lesions are combo of type III and type IV exposure to antigens stops further progression of disease.

– occur when there is impairment of the normal Pulmonary Defense Mechanism: 1. absent cough reflex 2. Damaged Mucociliary escalator 3. Deficiency in secretory IgA in bronchial mucus 4.↓phagocytic.bactericidal function of alveolar macrophages 5. Pulmonary congestion & edema 6. Presence …

Pulmonary Infections Occur when normal Pulmonary Defense Mechanisms Fail: 1. Loss of Cough Reflex = Coma / Anesthesia / Post-Op 2. Injury to Muco-Ciliary Escalator = Smoking / Squamous Metaplasia 3. IgA Deficiency (genetic / immunocompromised) 4. Decreased Macrophage Function …

Composition of Alveolar Wall Two components 1. Type 1 epithelium: -covers 95% of surface area, but constitutes 40% of epithelial cells. 2. Type 2 epithelium: -covers 5% of surface area, but constitutes 60% of epithelial cells. Characterization of ARDS Severe …

anatomic alteration of the lungs 1. Inflammation of alveoli 2. alveolar consolidation 3. atelectasis what happens with inflammation of lung with pneumonia fluid & red blood cells move into alveoli, leukocytes move into engulf & kill invading bacteria, macrophages appear …

pneumonia inflammation of the pulmonary gas exchange system – filling of the alveoli with cellular exudate Pneumonitis Inflammation of the lung, usually used to designate inflammation of the alveolar walls (interstitial pneumonia) WE WILL WRITE A CUSTOM ESSAY SAMPLE ON …

What is pneumonia? It can be one of three things, what are they? Inflammation of the parenchyma (membrane) of the lungs 1) bacterial, viral or mycoplasmal 2. Inhalation of toxic or caustics chemicals, smoke, dust or gases 3) aspiration of …

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