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
