L61 – Pulmonary Infections Flashcards by Max Kam

What is the most common form of lung infection?

Bacterial pneumonia

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What is the difference in name between viral and bacterial pneumonia?

Bacterial - pneumonia

Viral = Pneumonitis

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What is the route of transmission for bacterial pneumonia? Deposit where?

Inhale infectious droplets

deposit in terminal airways (respiratory bronchioles), and surrounding parenchyma

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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

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What are the bacteria that can cause pneumonia?

Streptococci, 
Staphylococci, 
Haemophilus influenza,
Pseudomonas, 
Klebsiella

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What is the acute response from lung tissue infected with pneumococcus?

acute, suppurative inflammation

neutrophil-predominant

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What is the early stage /changes in lung tissue in pneumonia?

Congested capillaries: vasodilation

- Edema: proteins, molecules leak into alveolar space

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What is the intermediate stage /changes in lung reaction in pneumonia?

Consolidation

Alveolar airspaces filled with exudate - fibrinous protein, neutrophils

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What are the 2 distributions of consolidation?

Bronchopneumonia

2. Lobar pneumonia

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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

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What is the Late stage/changes in lung reaction in pneumonia?

Neutrophils degenerate

Alveolar space with fibrin, more macrophages&raquo_space; clear up cell debris and exudates

> > resolution or complication

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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

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What is the CXR appearance of consolidated lungs?

Patchy (bronchopneumonia) or Diffuse (Lobar pneumonia) White shadows

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Are most cases bronchopneumonia or lobar?

Broncho

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What pathogen causes lobar pnuemonia?

Most commonly due to Streptococcus pneumoniae

Virulent factor = thick mucoid capsule

can spread quickly
throughout lungs

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Under what circumstances does lobar pneumonia occur instead of bronchopneumonia?

1) Aggressive pathogen
2) Immunocompromised/ suppressed
3) Delayed treatment

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What structure of lungs allow bacteria to spread quickly?

pores of Kohn

also known as interalveolar connections

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Describe bronchopneumonia appearance?

Patchy, bilateral, multifocal

Centred around terminal bronchioles

Consolidation is yellow, skinny, elevated

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What are the 2 severe, complicated outcomes for pneumonia?

Destroy lung parenchyma:

1) Patchy fibrosis
2) Necrosis and lung abscesses

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What gives the definitive diagnosis for pneumonia?

Culture studies of bacteria

Test antibiotic sensitivity

Use sputum or blood (due to bacteraemia)

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What are some systemic effects of pneumonia?

fever, malaise

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What are the chest symptoms and signs of pneumonia?

 Cough, sputum
 Reduced air entry on auscultation
 Bronchial breath sounds
 Crepitations
 Severe cases: shortness of breath, respiratory failure

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What causes the crepitations heard in pneumonia lungs>?

air passing through exudates, alveoli ‘pop open’

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Explain the bronchial breath sounds heard in pneumonia lungs?

vibrations transmitted through solid medium

dull on percussion

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Explain the reduced air entry on auscultation in pneumonia?

consolidated alveoli > 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?

No Due to reduced gas exchange

Haemoptysis is seen in which lung diseases?

TB Lung cancer some Strep infection

What is the most common direct cause of death in hospital patents? Why?

Pneumonia 2 reasons:  Indiscriminant use of broad spectrum antibiotics > cause change in normal flora, antibiotic resistance  Virulent organisms

What are the predisposing factors to pneumonia? VIIGUL

Virulent organism Immunocompromized hosts Impaired airway clearance General poor health / immune function Underlying viral bronchitis Lung congestion/ edema

What immunocompromize conditions can predispose to pneumonia?

Diabetes mellitus Cancer Chemotherapy Organ transplant patients

What causes impaired airway clearance and can predispose to pneumonia?

Smoking 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: Secondary pneumonia

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?

alveolocapillary block 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?

Heals fast 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?

Caseous necrosis Cavitation Calcification 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?

- Candida - Aspergillus >> aspergillosis (肺發霉) - Molds > Mucormyosis - Histoplasma > chronic granulomatous inflammation

Name some viruses that can cause opportunistic infections>?

cytomegalovirus (CMV), herpes simplex

What is the appearance of aspergillosis in the lungs?

Thread-like mass Hyphae is stained black by special dyes

What is the organism that very commonly causes fatal infections in AIDS patients in lungs?

Pneumocystis jirovecii

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

Describe Bronchoiectasis?

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?

 Pulmonary tuberculosis  Viral bronchitis complication >> necrotizing bronchial infection in childhood  Previous bronchopneumonia

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?

 Tumours  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?

Chest physiotherapy

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 position)

What is the severe clinical presentation of bronchiectasis?

Chronic hypoxia Pulmonary hypertension Abscess formation

Bronchiectasis can be diffuse or regional. Which region of the lung is most likely affected?

Lower lobe

L61 – Pulmonary Infections Flashcards

(79 cards)