Lecture 5: Lower Respiratory Tract Infection Flashcards
You visit an 80-year-old NZ European woman in a private hospital with the GP you are shadowing. She has a fever and is coughing up purulent sputum. She is in the private hospital because of advanced dementia and has been a resident for the past 3 years.
How can you decide if Beth has a self-limiting illness (viral URTI) or a potentially serious illness (pneumonia)?
To distinguish between upper respiratory tract infection (URTI, e.g. viral bronchitis) and lower respiratory tract infection (LRTI, e.g. pneumonia):
- Perform chest X-rays (CXR) on all patients (limited by lack or unavailability of resources, but increased access nowadays).
- Knowing patients’ _predisposing factors to pneumoni_a and clinical methods.
1) Are there signs of r_espiratory distress?_
2) Are there signs of focal lung disease?- (pus in lungs/alveoli)
Both indicate Penumonia not just bronchitis.
3) More dullness in percussion (for pneumonia), crackling when breathing (for bronchitis)
What are the Clinical Features To Distinguish Bronchitis From Pneumonia?
Organisms that cause these two diseases are different, and epithelium lining different segments of airways are also different.
- Pneumonia is infection in alveolar air spaces, and in the terminal and respiratory bronchioles.
- Bronchitis is infection of c_onducting airways._
Bronchitis doesn’t require treatment, but pneumonia does!
Colour of sputum is not indicative of an infection! Green/yellow sputum is due to inflammatory cells and cell debris present.
Associated symptoms such as runny nose, i_rritated and itchy eyes_ and sore ears can lead to differential diagnosis.
Pneumonia is infection in _____________and________
Bronchitis is infection of _______________
Does the colour of sputum indicate infection?
Colour of sputum is not indicative of an infection!
Green/yellow sputum is due to i_nflammatory cells and cell debris_ present.
What are the signs of Pneumonia in elderly patients?
Signs of pneumonia in young patients are usually obvious, but in elderly patients they do change.
Pneumonia in the elderly:
- Increased respiratory rate in 69% (difficulty breathing so compromised gas transfer, which involves alveoli)
- Crackles in 80%
- Consolidation in 30% (Lung is full of liquid- this includes signs such as dullness to percussion and bronchial breath sounds).
- Fever and chills in 50%
- Non-pulmonary in 20% (mainly confusion and delirium)
Diagnose
CXR shows pneumonia of left lung and right upper lobe.
- The l_eft lung is very diseased._
- The h_orizontal fissure of right lung_ is highlighted because of the presence of consolidation in the right upper lobe of right lung.
It is also possible to identify the presence of an endotracheal tube in the trachea, most likely to establish an airway in this patient.
Where is the penumonia?
Pneumonia is in the right lower lobe
(cannot see the diaphragm due to the dense lung sitting on top of the dense diaphragm)
- you cannot follow the lines of the lung
Where is the pneumonia?
Right upper lobe
(above the right horizontal fissure)
Where is the penumonia?
CXR shows pneumonia of left lobe (opacity).
It is not possible to see heart or left hemidiaphragm, because there is loss of the interface between the lung (air) and muscle (hemidiaphragms).
What are the risk factors for penumonia?
The most important risk factors for pneumonia are the following:
- Age below 2 or above 65:
- Impairment of some significant manner, e.g. inability to mobilise, dysphagia (risk factor for aspiration pneumonia).
- Co-morbid conditions, e.g. cardiopulmonary disease
- Hospital exposure (increased exposure to pathogens), e.g. ventilator-associated pneumonia
- Chronic lung disease
- Smoking (mucociliary escalator is paralysed from cigarette toxins)
- Immune dysfunction (various forms), e.g. advanced HIV infection are at increased risk of streptococcal pneumonia.
How do people develop penumonia?
Aspirate from our upper airways fall into the lower airways)
Our immune systems are pretty good at getting rid of it
But if a larger number get into our lungs than we can clear, we can get penumonia.
Of the following, what % are usually caused by bacteria and what % are caused by viruses?
- Mastoiditis
- Pharyngitis
- Epiglotitis
- Bronchitis
- Penumonia
- Mastoiditis is entirely bacterial
- Pharyngitis is mostly viral with some bacterial causes (GAS)
- Epiglottitis is entirely bacterial (life-threatening infection caused by Haemophilus influenzae type B (HiB), rare due to vaccine success)
- Bronchitis is entirely viral
- Pneumonia is entirely ‘bacterial’ (requires antibiotics!) (usually caused by H influenzae and S pneumoniae)
What microbial agents cause Penumonia?
Microbial agents causing community acquired pneumonia include:
- Streptococcus pneumoniae (very common)
- Haemophilus influenza (relatively common)
- Staphlococcus aureus (not very common)
- Influenza virus and other viruses
- S. aureus is not a very common cause of pneumonia
- Gram negative bacteria in the gut such as E. coli and K. pneumoniae can cause pneumonia. They become more prevalent causes of pneumonia in a hospital setting, and they are less common in a community setting (quite rare).
All pneumonia occurs through microaspiration! Perfectly healthy individuals microaspirate everyday (normally when asleep).
All pneumonia occurs through _______________!
All pneumonia occurs through microaspiration! Perfectly healthy individuals microaspirate everyday (normally when asleep).
Streptococcus pneumoniae is an _______streptococcus, and is part of ______ group of streptococci (relate to strep. mitis).
It is different due to its ______ and sensitivity to ______.
Streptococcus pneumoniae is an alpha-haemolytic streptococcus, and is part of viridans group of streptococci (relate to strep. mitis). It is different due to its high virulence and sensitivity to optochin.
Describe Streptococcus Pneumoniae
Streptococcus pneumoniae is an alpha-haemolytic streptococcus, and is part of viridans group of streptococci (relate to strep. mitis). It is different due to its high virulence and sensitivity to optochin.
- It commonly _colonises the nasopharynx (_5-10% adults and 20-40% children)
- Prevalence of colonisation i_ncreases in winter_
- In adults, colonisation persists for a few weeks
It is a pathogen that p_rimarily causes pneumonia,_ but it can cause invasive diseases such as bacteremia/septicaemia, septic arthritis (quite common), bacterial meningitis (esp. young patients and elderly, rare in adults).
Describe the study that showed that bacteria share DNA
For two different colonies, the right ones are expressing a polysaccharide capsule and the left ones are not. In bacteria that are expressing capsule, the cells are larger and the colonies are mucoid.
- In the presence of dead S pneumoniae (express the capsule), alive S pneumoniae (not expressing capsule) took up the genes for the capsule and formed capsules
- Some of bacterial cells in colonies die through apoptosis, and r_elease their DNA contents into the environment,_ so that neighbouring bacterial cells can take it up
The capsule is a v_ery important virulence facto_r in causing disease, and without it, it is not possible for bacteria to cause disease.
Describe 6 Virulence factors S.Pneumoniae have
- Polysaccaride capsule prevents opsonization by antibodies (e.g. IgG) and complement (esp. C3b).
- Pili (similar to scaffolding) contribute to colonisation and cytokine production (TNFa) during invasion
- Pneumococcal surface protein C (PspC) is a protein tha_t prevents complement activation/cascade_
- Pneumococcal surface protein A (PspA) binds to epithelial cells and also prevents the deposition of C3b.
- Choline binding protein binds to Ig receptors on epithelial cells (allows transport into cells).
- Pneumolysin (toxin) lyses neutrophils and epithelial cells.
If Beth has penumonia, confirmed by CXR what investigations does she require?
We might want to know what type of organism is causing the disease, to see if that knowledge will improve patient outcome (if determining the cause of pneumonia increases patient outcomes, then we should look for a cause of the disease).
(see the photo)
The other line of clinical thinking should relate to severity of illness in the patient.
- If patient is not particularly unwell, then it is likely that treatment is not going to be very intense (oral antibiotic and patient might be able to go home).
- However, the treatment is going to be more vigorous if the patient has a chance of dying. It is in the latter patients where the clinician has to think hard about the type of treatment they will give the patient, which is decided upon after a number of tests have been carried out.
In cases of mild community-acquired pneumonia (in otherwise healthy young individuals), outcome is usually very good. They can be given antibiotics to treat S. pneumoniae and they will be fine. In people who are sicker and chance of mortality, they are going to require hospitalisation and investigations into the cause.
Describe Antibiotics and S.pneumoniae
S pneumoniae is main bacterial species that we need to be concerned with, and this can usually be treated with penicillin
- Penicillin _resistance is increasin_g.
- It is mediated by altered PBP/transpeptidase, which reduces penicillin binding affinity (MRSA)
-
Oral dosing might be inadequate, IV dosing will be okay.
- It is important consideration when treating meningitis caused by S pneumoniae)
- Penicillin resistance is associated with resistance to other antibiotics.
- In parts of the world where this is common, oral antibiotics with excellent activity against penicillin-resistant pneumococci are used e.g. quinolones, recently developed macrolides or ketolides.
There are other antibiotics that can be used if the patient is allergic to penicillin, or pathogen that is not S pneumoniae.
More Penicilin used in a country, the greater the chance of S.Pneumoniae resistance. (France - high use, high resistence)
