Pathology of respiratory tract infection Flashcards
What are the different types of microorganism pathogenicity?
Primary, these are highly infectious and dangerous
Facultative- need the immune system to be slightly reduced/weakened to infect
Opportunistic- require the hosts immune system to be greatly reduced so that the can infect the host (the host must have a compromised immune system)
What groups of patients have a compromised immune system?
Elderly
Patients on immunosuppressants (such as after transplant surgery)
Infants
What does a patients ability to resist infection depend upon?
State of the host’s defence mechanisms (their immune system)
The age of the patient
What are the two categories of respiratory tract infection?
Upper (from larynx up) and Lower
Give examples of upper respiratory tract infections
Common cold (Coryza) Sore throat syndrome Acute Laryngotracheobronchitis (Croup) Laryngitis Sinusitis Acute Epiglottitis
What microorganisms can cause Acute Epiglottitis?
Haemophilus influenzae type B
Group A beta haemolytic streptococci
(others can cause it)
Name some viruses that commonly cause upper respiratory tract infection
Rhinovirus Influenza Adenovirus EB Virus Parainfluenza
Give a few examples of lower respiratory tract infections.
Bronchitis
Bronchiolitis
Pneumonia
What is the main respiratory tract defence mechanism?
Macrophage-mucociliary escalator
How does the macrophage-mucociliary escalator work?
Macrophages engulf and digest foreign bodies that make it to the alveoli and respiratory bronchioles. These macrophages them stick in the mucus and get transported with the dust and bacteria, up the respiratory tract by the cilia which move the mucus along.
The cilia move the bacteria and pathogens out of the lower respiratory tract and they get swallowed in a cough reflex (or expelled out of your nose or mouth)
What are the other mechanisms that are in place as defence mechanisms?
General immune system- humoral and cellular immunity
Respiratory tract secretions
Upper respiratory tract acts as a filter
What happens when ciliated epithelium is lost?
The air breathed in will not be humidified and warmed.
The mucociliary escalator will also be lost in that area, this means that bacteria and pathogens won’t be removed from that area or anywhere below it. Therefore secondary infections are likely.
Name one instance in which the ciliated epithelium can be lost
Influenza
What microorganisms cause a common cold?
Rhinovirus
Human parainfluenza virus
What microorganisms cause Croup?
Respiratory Syncytial virus
Parainfluenza virus
Rhinovirus
What are the three methods for classifying pneumonia?
Anatomically
Aetiologically (how the infection occurred)
Microbiologically
Name the classes on pneumonia in aetiological classification of Pneumonia
Community Acquired Pneumonia Hospital Acquired (Nosocomial) Pneumonia Pneumonia in the immunocompromised Atypical pneumonia Aspiration pneumonia Recurrent pneumonia
What are the patterns of pneumonia?
Bronchopneumonia- affects the bronchioles and surrounding alveolar tissue
Segmental
Lobar- affects one or more lobes
This tells you how much of the lung is infected.
Give some types of pneumonia
Hypostatic- associated with elderly and bed ridden people who remain in the same position for long periods of time, which causes areas of decreased ventilation in the lungs.
Obstructive
Retention
Endogenous lipid/ lipoid
What is bronchopneumonia?
It is pneumonia that affects the bronchioles and the surrounding alveolar tissue. This tends not to spread to large areas of the lungs and doesn’t usually reach the pleura, so there are no pleural complications.
What does bronchopneumonia usually look like on the x-ray?
Often bilateral
Causes patchy basal opacification (white areas) where consolidation has occurred.
Doesn’t usually occur in young people.
Generally occurs in people with other health issues and is caused by facultative pathogens.
What are the possible outcomes or complications of pneumonia?
Resolve
Pleurisy (inflammation of the pleura)
Pleural effusion- collection of fluid in the pleural space
Empyema (chronic empyema sometimes never goes away)
Organisation: mass lesion,cryptogenic organising pneumonia (COP), Constrictive bronchiolitis
Lung abscess
Bronchiectasis
What is organisation?
It is when a healing process is occurring and the exudate heals/forms scar tissue rather then undergoing reabsorption and resolution.
What can cause lung abscesses to form?
Obstructed bronchus (possibly obstructed by a tumour)
Aspiration
Microorganisms
Necrotic lung tissue (the abscess would then be a secondary infection)
