Pathology of Respiratory Tract Infections Flashcards
What are different kinds of microorganisms in terms of pathogenicity?
Primary
Facultative
Opportunistic
What three factors affect the affect likelihood of a lung infection?
- microorganism pathogenicity
- capacity to resist infection
- population risk
What is a primary microorganism?
a microogranism able to infect anyone
What is a fucultative microorganism?
a microorganism that needs a little ‘help’ when infecting a host eg. the host is less able to resist infection.
What is an opportunistic microorgansim?
a microorganism that can’t infect a host unless the hosts capacity to resist infection is very compromised.
What two factors affect a patient’s capacity to resist infection?
- state of defence mechanisms
- age of patient
What are some upper respiratory tract infections?
6 points
Coryza (common cold) Sore throat syndrome Acute laryngotracheobronchitis (coup) Laryngitis Sinusitis Acute epiglottitis
What is acute epiglottis commonly caused by?
Group A beta-haemolytic Streptococci
Haemophilus influenza
When is acute epiglottiitis a problem?
- children
- trachea is smaller
- inflammation of the epiglottis may cause the airway obstruction.
What are some examples of lower respiratory tract infections?
(3 points)
bronchitis
bronchiolitis
pneumonia
Outline some respiratory tract defence mechanisms?
4 points
- Macrophage-mucociliary escalator system
- General immune system
- Respiratory secretions
- Upper respiratory tract as a filter
What is the macrophage-mucociliary escalator system composed of?
(3 points)
- Alveolar macrophages
- Mucociliary escalator
- Cough reflex
How are particles and microorganisms removed from the terminal bronchioles and proximal alveoli?
Macrophages phagocytose particles and pathogens then transport to lymph nodes via lymph
Where does the mucociliary escalator begin?
Respiratory bronchioles
How does the upper respiratory tract help to prevent the lower respiratory tract from becoming infected?
Warms and humidifies air, supplying a large surface area where material in the air may be deposited so it does not reach the lower respiratory tract.
How are particles cleared from the lungs?
Macrophage-mucociliary escalator:
1) Macrophages clear particles by phagocytosis
2) Leave via the muco-ciliary escalator or through lymph.
How can the influenza virus cause bacterial lung infections ?
- influenza virus is cytopathic
- destroys the cells of the mucociliary escalator
- defence mechanism to bacteria is compromised
- secondary infection is much more likely
How can pneumonia be classified?
3 points
- Anatomical (understand radiology)
- Aetiological (how acquired, circumstances)
- Microbiology (tells us how to treat the patient)
What are the further aetiological classifications of pneumonia?
(6 points)
- Community acquired
- Hospital acquired (nosocomial)
- Pneumonia in the immunocompromised (e.g. HIV)
- Atypical pneumonia (caused by unusual organism)
- Aspiration pneumonia
- Recurrent pneumonia
What are some different patterns of pneumonia?
6 points
- Bronchopneumonia
- Segmental
- Lobar
- Hypostatic (elderly)
- Aspiration
- Obstructive, retention, endogenous lipid
What is hypostatic pneumonia?
- usually occurs in elderly people with cardiac failure
- extra secretions in the lung, oedema in the lung or suppressed cough reflex.
- All these thing leads to accumulation of fluid in the lung which acts as a ‘petri dish’ for bacteria.
What is bronchopneumonia?
- acute inflammation
- very local areas of the lung,
- Pus from polymorphs replaces air, this is called local consolidation.
- Accumulation of neutrophils in alveolar space
What is local consolidation?
The building of pus in certain localise areas in the lung during a pneumonia infection.
What are infections from hospital more likely to be?
Resistant to antibiotics
What is bronchopneumonia characterised by?
- Spots of infection stay around alveoli
- Rare for infection to reach the pleura
- Basal parts of the lungs infected
- bilateral
What does bronchopneumonia look like on an x-ray?
- often bilateral
- basal site of lung
- patchy opacification
Where is bronchopneumonia most likely to be found in the lungs?
Base
Is pleural effusion likely in bronchopneumonia?
No.
The infection is isolated in specific areas and so won’t spread to the pleura.
What is lobar pneumonia characterised by?
- Large amount of lung infected by the same inflammatory process.
- Could be an entire lobe.
- Meaning the whole part is airless due to being filled with pus.
What causes lobar pneumonia?
Caused by a primary pathogen, infects a whole lobe as the body’s response to the pathogen is vigorous.
What does lobar pneumonia look like on an xray?
Complete opacification of one lobe only.
How does segmental and lobar pneumonia differ from bronchopneuonia?
Segmental and lobar are at a single site whereas broncho is multi-locational.
What kind of pneumonia could lead to a pleural infection?
Lobar, pleural infections are rare with bronchopneumonia as the infection does not reach the pleura.