Pathology of respiratory tract infections Flashcards
What types of Microorganism Pathogenicity exist How invasive it is, infectivity etc ?
Primary - very invasive and infectious to healthy people
Facultative (most common)- A bit of illness needed for invasion to occur
Opportunistic -cause infections in immunocompromised host
What are common upper respiratory tract infections ?
Coryza- common cold Sore throat syndrome Acute laryngotracheobronchitis (croup) Laryngitis Sinusitis Acute epiglottitis
What does the capacity to resist infection depend on ?
State of Host Defence Mechanisms Age of Patient
What are some examples of upper respiratory tract infections ?
Coryza- common cold Sore throat syndrome Acute laryngotracheobronchitis (croup) Laryngitis Sinusitis Acute epiglottitis
What causes acute epiglottis ?
Group A beta-haemolytic Streptococci Haemophilus influenzae (type b - Hib) Rarely caused by Parainfluenza virus type 4 but other viruses may also be responsible
What are the effects of acute epiglottitis ?
Potentially life threatening
Affects children
Swells up and obstructs airway
Causes extreme respiratory difficulty
What are some examples of lower respiratory tract infections ?
Bronchitis
Bronchiolitis
Pneumonia
How do lower respiratory tract infections compare to upper ?
More morbidity and mortality rate with lower respiratory tract infections
What are the respiratory tract defence mechanisms ?
Macrophage-mucocilary escalator system
- alveolar macrophages - mucocilary escalator - cough reflex
General immune system
- humoral and cellular immunity
Respiratory tract secretions
Upper respiratory tract as a filter
Which part of the respiratory tract is sterile ?
Lower
Which part of the upper respiratory tract acts as a filter ?
Nose
What components of the the upper respiratory tract as a filter ?
Hair, moist, mucous and cilia in epithelium
What is the effect of alveolar macrophages ?
Phagocytose, (if they cannot digest) travel towards the ciliary escalator for digestion
Why might the macrophage pass through the alveolar membrane ?
To reach Interstitial pathway via lymph to the lymph nodes
Where does particle deposition occur ?
Deposition on the conducting airways
Deposition on the terminal bronchioles/ proximal alveoli
How can the ciliary escalator fail ?
Viral infections (influenza) – damage to normal respiratory epithelium – no longer functional or cilia, severe when there is no mucocilary membrane Common cause of bacterial chest infections
What are the 3 classifications of pneumonia ?
Anatomical
Aetiological
Microbiological
What are the aetiological classifications of pneumonia ?
Community Acquired Pneumonia (usually treated by GP’s)
Hospital Acquired (Nosocomial) Pneumonia (more likely to be severe, bacteria more likely to be resistant)
Pneumonia in the Immunocompromised (AIDS patients)
Atypical Pneumonia (unusual infectious agents)
Aspiration Pneumonia (result in the inhalation of gastric content)
Recurrent Pneumonia – signal that there is something particularly odd going on)
What are the different patterns of pneumonia ?
Bronchopneumonia
Segmental
Lobar
Hypostatic
Aspiration
Obstructive, Retention, Endogenous Lipid
What does bronchopneumonia affect ?
Both lungs and the bronchi
What does lobar pneumonia affect ?
One or more sections/ lobes of the lung
What causes most cases of bacterial pneumonia ?
Streptococcus pneumonia- main one
Staphylococcus aureus
Haemophilus influenzae
Klebsiella pneumoniae
What is the classic type of pneumonia that is community acquired ?
Shows lung consolidation of one lung segmental lobe
What is hypostatic pneumonia ?
Infection in the dependent portions of the lungs due to decreased ventilation of those areas
Failure to drain bronchial secretions
Occurs primarily in old people or those debilitated by disease who remain recumbent in the same position for long periods
What is aspiration pneumonia ?
Aspiration pneumonia is a lung infection that develops after you aspirate (inhale) food, liquid, or vomit into your lungs
What causes aspiration pneumonia ?
Vomiting
Oesophageal Lesion
Obstetric Anaesthesia (any anaesthetic used in childbirth)
Neuromuscular Disorders Sedation
Where is the most common location for aspiration pneumonia ?
Apical segment of right lower lobe
What is the effect of acute inflammation in bronchopneumonia ?
Lung filled with pus, neutrophils and inflammatory exudate
It is the most common hypostatic pneumonia story
How does the action of bacteria differ in lobar pneumonia ?
Organisms are more aggressive, greater tissue reaction, greater spread of organism. Infection stops at the pleura
What are the outcomes/ complications of pneumonia ?
Most Resolve
Pleurisy, Pleural Effusion and Empyema
Organisation – formation of fibrous tissue, inflammatory area becomes scar tissue
–mass lesion
–COP(cryptogenic organising pneumonia (BOOP))
–Constrictive bronchiolitis
Lung Abscess - necrosis, hole in lung
Bronchiectasis
Pneumonia is still a potentially fatal disease
What happens during the organisation in pneumonia ?
Formation of fibrous tissue, inflammatory area becomes scar tissue
What is a lung abscess ?
Pus forms in the space where there was tissue destruction
What organisms are more likely to cause abscess ?
Staph aureus
Some pneumococci
Klebsiella
When is lung abscess metastatic ?
Pyaemia
What can happen if there is secondary infection in a lung abscess ?
Necrotic lung
What is the mechanism of bronchiectasis ?
The mechanism of disease is breakdown of the airways due to an excessive inflammatory response Involved airways (bronchi) become enlarged and thus less able to clear secretions These secretions increase the amount of bacteria in the lungs, result in airway blockage and further breakdown of the airways
What is bronchiectasis ?
Abnormal dilation of the bronchi in the periphery of the lung
what is bronchiectasis due to ?
Severe infective episode
Recurrent infections- many causes
Proximal bronchial destruction
Lung parenchyma destruction
What are the symptoms of bronchiectasis ?
Cough
SOB
Abundant purulent foul sputum
Coughing up blood (haemoptysis)
What are the signs of bronchiectasis ?
Coarse crackles
Clubbing
How might you get a recurrent lung infection ?
Local Bronchial Obstruction - Tumour, Foreign body?
Local Pulmonary Damage - Bronchiectasis?
Generalised Lung Disease - Cystic Fibrosis?, COPD?
Non-Respiratory Disease - Immunocompromised (HIV, other)?, Aspiration?
What are Oppurtunistic pathogens and can you give an example of one ?
Infection by organisms not normally capable of producing disease in patients with intact lung defences
–Pneumocystis jirovecii
