T4 L8: Respiratory tract infections Flashcards
Which 2 innate immunity features are in the lungs?
cilia and alveolar macrophages
Which 3 acquired immunity features are in the lungs?
B cells, T cells, and igA
What is empyema?
Puss in the pleural spaces
What is pneumonia?
Filled airspaces in the lungs
What are pulmonary abscesses?
Puss-filled dead areas
What is the most common upper respiratory tract infection?
Rhinovirus
How does Bradykinin cause symptoms of the cold?
Causes a sore throat and it may cause nasal congestion due to vasodilatation
How is sneezing mediated?
By histamines. Stimulation of the trigeminal sensory nerves
What protein causes nasal discharge colour change?
myeloperoxidase
What nerve mediates a cough?
The vagus nerve but the inflammation has to spread to the larynx to cause this
Which proteins are responsible for systemic symptoms like fever?
Cytokines
What are some differences between the cold and the flu?
Cold
- appears gradually
- usually no fever
- able to function
Flu
- quick onset
- high fevers
- unable to function normally
Which 4 groups are at risk of complication of the flu?
Immunosuppressed, pregnancy or 2 weeks post partum, age <2 or >65years, or BMI >40
What are the H proteins on an influenza virus?
Haemagglutinin proteins which bind to sialic acids on the surface to glycoproteins. They allow the virus to enter the cell
What are the N proteins on an influenza virus?
Neuraminidase proteins that allow the virus to escape by cleaving sialic acid bonds otherwise they would all clump up together
What is antigenic drift?
Small mutations that occur each time a virus replicates its DNA/RNA
What us antigenic shift?
Big mutations that occur in entire sections of the genome. This is special for influenza A
When is antigenic shift most likely to occur?
When the host is already infected with another virus
Which proteins on a influenza virus under go antigenic shift and drift?
The H and N proteins
What is pneumonia?
Infection of lung parenchyma
What is the lung parenchyma?
Portion of the lung involved in gas exchange
How would you diagnose pneumonia?
Using a CXR with supporting clinical features
What is consolidation?
Alveoli and bronchioles are completely filled with inflammatory fluid so they appear solid
How would pneumonia appear on a CXR?
White parts all over the lung. The heart and diaphragm borders will be obscured because of loss of clear alveoli
Why is community vs hospital acquired pneumonia classified?
Because pathogens involved will differ which alters management
What are some community-acquired pneumonia pathogens?
Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella pneumophila, Staphylococcus aureus
What is the commonest organism behind pneumonia?
Streptococcus pneumoniae
What type of bacteria is streptococcus pneumoniae and what is the treatment?
A gram negative cocci treated with penicillin
Which part of the body does streptococcus pneumoniae attach to primarily?
In the nasopharynx
What are the risk factors for a streptococcus pneumoniae infection?
Alcoholics, respiratory disease, smokers, hypersplenism, chronic heart disease, HIV
What is the commonest cause of ambulatory ‘atypical pneumonia’ and what does that mean?
Mycoplasma pneumoniae meaning it attacks more mildly but is more persistent than typical pneumonia
What is the treatment for mycoplasma pneumoniae?
Macrolides and tetracyclines (they attack ribosomes)
Why can’t mycoplasma pneumoniae be treated with penicillins?
It lacks a cell wall so is resistant to penicillin’s. It also cannot be grown on normal lab plates
How do Legionella pneumophilia infections occur?
Sporadic infections associated with outbreaks of contaminated water associated with travelling. It’s very rare
How would you diagnose Mycoplasma pneumoniae?
A PCR of throat swab (VTS)
How would you diagnose Legionella pneumiphila?
Urinary legionella antigen
What is the treatment for Legionella pneumophila?
Macrolides and quinolones
What proportion of the world has latent TB?
A quarter of the worlds population
Describe TB as a cell
Aerobic bacillus, often referred to as acid-fast bacillus (AFB). It has a cell wall but lacks the phospholipid outer layer
What stains are used for TB?
Zhiel-Neelsen or auramine-rhodamine stains
Why is TB referred to as acid fact bacillus?
Because it retains stains after treatment with acids
Which infection develops in granulomas and how?
TB. T cells, B cells and activated macrophages establish granulomas which contain TB where the pathogen survives
What is meant by latent TB?
The bacilli are dormant and contained within host defences. Its non-infectious and asymptomatic
What is meant by active TB?
Actively replicating bacilli, may be infectious and is symptomatic
