Flashcards in L61 – Pulmonary Infections Deck (79):
What is the most common form of lung infection?
What is the difference in name between viral and bacterial pneumonia?
Bacterial - pneumonia
Viral = Pneumonitis
What is the route of transmission for bacterial pneumonia? Deposit where?
Inhale infectious droplets
deposit in terminal airways (respiratory bronchioles), and surrounding parenchyma
How does bacteria in terminal airways attract neutrophils?
Bacteria deposit in parenchyma and terminal ariway
> establishment of growth
> macrophages enter alveolar space and produce chemotaxis factors
> Attract neutrophils
What are the bacteria that can cause pneumonia?
What is the acute response from lung tissue infected with pneumococcus?
acute, suppurative inflammation
What is the early stage /changes in lung tissue in pneumonia?
- Congested capillaries: vasodilation
- Edema: proteins, molecules leak into alveolar space
What is the intermediate stage /changes in lung reaction in pneumonia?
Alveolar airspaces filled with exudate - fibrinous protein, neutrophils
What are the 2 distributions of consolidation?
2. Lobar pneumonia
Compare and describe bronchopneumonia and Lobar pneumonia in their extent of consolidation?
-Broncho = , bilateral, patchy/ multifocal,
>> centered around terminal bronchioles
-Lobar = diffuse conslidation
>> involving most / all of a lobe / whole lung
What is the Late stage/changes in lung reaction in pneumonia?
Alveolar space with fibrin, more macrophages >> clear up cell debris and exudates
>> resolution or complication
During which stage of pneumonia infection does red hepatization and grey hepatization occur?
Red = Intermediate stage = lungs appear firm, solid, red due to congested blood capillaries
Grey = Late stage = lungs become less congested
What is the CXR appearance of consolidated lungs?
Patchy (bronchopneumonia) or Diffuse (Lobar pneumonia) White shadows
Are most cases bronchopneumonia or lobar?
What pathogen causes lobar pnuemonia?
Most commonly due to Streptococcus pneumoniae
Virulent factor = thick mucoid capsule
can spread quickly
Under what circumstances does lobar pneumonia occur instead of bronchopneumonia?
1) Aggressive pathogen
2) Immunocompromised/ suppressed
3) Delayed treatment
What structure of lungs allow bacteria to spread quickly?
pores of Kohn
(also known as interalveolar connections)
Describe bronchopneumonia appearance?
Patchy, bilateral, multifocal
Centred around terminal bronchioles
Consolidation is yellow, skinny, elevated
What are the 2 severe, complicated outcomes for pneumonia?
Destroy lung parenchyma:
1) Patchy fibrosis
2) Necrosis and lung abscesses
What gives the definitive diagnosis for pneumonia?
Culture studies of bacteria
Test antibiotic sensitivity
Use sputum or blood (due to bacteraemia)
What are some systemic effects of pneumonia?
What are the chest symptoms and signs of pneumonia?
Reduced air entry on auscultation
Bronchial breath sounds
Severe cases: shortness of breath, respiratory failure
What causes the crepitations heard in pneumonia lungs>?
air passing through exudates, alveoli ‘pop open’
Explain the bronchial breath sounds heard in pneumonia lungs?
vibrations transmitted through solid medium
dull on percussion
Explain the reduced air entry on auscultation in pneumonia?
> quiet breath sounds
What is the appearance of sputum in pneumonia?
contains neutrophils > thick yellowish-green
Is the reduced gas exchange in pneumonia a ventilation problem?
Due to reduced gas exchange
Haemoptysis is seen in which lung diseases?
some Strep infection
What is the most common direct cause of death in hospital patents? Why?
Indiscriminant use of broad spectrum antibiotics > cause change in normal flora, antibiotic resistance
What are the predisposing factors to pneumonia?
Impaired airway clearance
General poor health / immune function
Underlying viral bronchitis
Lung congestion/ edema
What immunocompromize conditions can predispose to pneumonia?
Organ transplant patients
What causes impaired airway clearance and can predispose to pneumonia?
Loss of cough reflex (e.g. after surgery)
Immobile ciliary apparatus (e.g. hereditary)
How does cystic fibrosis predispose pneumonia?
Accumulation of secretions > medium for bacteria growth
How does underlying viral bronchitis predispose pneumonia?
Viral bronchitis > Necrosis of bronchoepithelial space:
What are infections caused by pneumonia spreading?
Adjacent organs - pleuritis, pericarditis, empyema thoracis
Distant organs - meningitis, arthritis
Describe how pneumonia can destroy lung parenchyma via fibrosis?
During healing, tufts of fibrous tissue grow into alveolar spaces to cause scarring of lung
>> organization, patchy fibrosis
Describe the formation of lung absecesses? What is the CXR appearance?
necrosis of lung tissues > patches coalesce to become confluent > form cavity surrounded by congestion and fibrosis
Chest X-ray: roundish cavity contains pus, air
Describe the formation of Empyema Thoracis and the appearance?
Pus forms in the thoracic cavity due to spread of infection from lung
Yellow pus covers lung surface
Viral, mycoplasma infections occur in which tissues?
Cause interstitial pneumonitis at:
1) Epithelium (e.g. type I pneumocytes)
2) interstitium (peribronchial, peribronchiolar, alveolar wall tissues)
In interstitial pneumonitis, why is CXR not used for diagnosis?
Airspace not affected > CXR appear normal
What is the tissue response in interstitial pneumonitis?
Congested, dilated capillary
Interstitial edema (predominantly mononuclear exudates)
Hyperplasia of type II pneumocytes
What infiltrates the interstitium in interstitial pneumonitis?
Interstitial tissue is infiltrated by lymphocytes, macrophages, plasma cells
What is the normal and abnormal resolution of Interstitial pneumonia?
Most = self-limiting, heal without complications
Rare cases= severe extensive damage: Diffuse Alveolar Damage (DAD)
How does DAD cause shortness of breath?
cells lining alveoli die
>> protein-rich edema fluid, macrophages, PMNs leak into alveolar airspace
>> Hyaline membrane
>> acute respiratory distress
What are the mild clinical features of interstitial pneumonia?
dry cough without sputum
What are the severe clinical features of interstitial pneumonia?
impaired oxygen diffusion > hypoxia
Shortness of breathe
What is the route of transmission for mycobacterial infection?
breathe in infectious droplet nuclei in atmosphere
Location of mycobacterial infection in lungs?
In lung parenchyma and lymph nodes
Systemic spread may occur (e.g. meningitis, kidney, bone necrosis)
Why does mycobacteria cause chronic inflammation? How does it persist?
Persist in macrophages
Cause chronic inflammation and become reactivated when immune system is weak
What is left after first mycobacteria infection?
Leaves small scar in lung or lymph nodes
What reaction occurs when Mycobacteria is reactivated in body?
sensitized T cells
Type IV hypersensitivity reaction
Form granulomas, tissue caseous necrosis
What is Miliary TB?
systemic spread of TB causing multiple small granulomas
Describe the morphology of Mycobacterial granuloma?
Tissue necrosis surrounded by epitheloid histocytes, Langhans giant cells, lymphocytes and fibroblasts
Describe the morphology of epitheloid histocyte and Langhans giant cells?
Epithelioid histiocytes (more cytoplasm, elongated, slipper-like nucleus)
Langhans giant cells (macrophage with multiple
nuclei at periphery, horseshoe-like appearance)
How is Mycobacteria demonstrated in culture?
demonstrate acid-fast bacilli (AFB)
by Ziehl-Neelsen stain (appears red)
What is the other method to confirm Mycobacteria granuloma apart from culture?
PCR on bronchial fluids
What is the gross appearance in pulmonary tuberculosis?
Scarring and fibrosis
What causes opportunistic infections?
by organisms that are usually not pathogenic in healthy people > affect immunocompromized hosts
Usually mixed infections by different organisms
How can fungus infect healthy hosts?
In pre-existing cavities (saprophytic growth)
form colonies without tissue invasion
How can fungus cause hemmorhagic infarct in immunocompromised patients?
Hungal hyphae through arterial wall in lungs > cause pulmonary haemorrhage
> hemorrhagic infarct and haemoptysis
What are some fungus that can cause opportunistic infections?
-Aspergillus >> aspergillosis (肺發霉)
-Molds > Mucormyosis
-Histoplasma > chronic granulomatous inflammation
Name some viruses that can cause opportunistic infections>?
What is the appearance of aspergillosis in the lungs?
Hyphae is stained black by special dyes
What is the organism that very commonly causes fatal infections in AIDS patients in lungs?
How is Pneumocystis jirovecii detected?
Detectable in sputum
Best demonstrated in bronchoalveolar lavage:
Specimen reveals frothy sputum, ball like exudate in form of alveolar cast
What is the stain for pneumocystis jirovecii?
Grocott stain stains PJ cysts > stains black
permanent, irreversible dilatation of bronchi, large bronchioles
What are the 2 causes bronchiectasis?
1) Related to chronic infection (with necrosis and obstruction of bronchial wall)
2) Related to Bronchial obstruction
Vicious cycle of obstruction and infection
What are some infections that can lead to Bronchiectasis?
Viral bronchitis complication >> necrotizing bronchial infection in childhood
What are some LUMINAL bronchial obstructions that can lead to Bronchiectasis?
Mucus, sputum, inflammatory exudate
Foreign body (especially young children)
Impaired mucus clearance
What are some MURAL bronchial obstructions that can lead to Bronchiectasis?
Previous bronchial wall infection, scarring (e.g. TB, cancer)
What are some Extrinsic/ compression bronchial obstructions that can lead to Bronchiectasis?
enlarged lymph nodes outside bronchi
Explain the vicious cycle of obstruction and infection in bronchiectasis?
Bronchial obstruction = accumulation of bronchial secretion
> chronic bacterial infection
> Progressive necrosis, weakening of bronchial wall, scarring
> Bronchial secretion cannot drain
> further obstruction and infection
What causes the bronchial wall to dilate in bronchiectasis?
Infection causing weakened and scarred bronchial wall
>> During INSPIRATION, Negative thoracic pressure pulls on weakened bronchial wall
>> Bronchial dilation
What is the treatment for the accumulation of mucus and pus in lungs?
What are some complications of Bronchiectasis?
lung abscess, distant spread of infection
What is the signature clinical presentation of bronchectasis?
Copious foul-smelling sputum, induced by postural change (e.g. change sleeping
What is the severe clinical presentation of bronchiectasis?