Pneumonia

Question 1

What is pneumonia

Answer 1

Inflammation of the lung parenchyma (i.e. alveolar spaces) due to an ineffective agent.

Question 2

What are the 2 pathological classifications of pneumonia?

Answer 2

lobar vs bronchopneumonia

Question 3

Bronchopneumonia

Answer 3

characterised by widespread patchy inflammation centred on the airways. It is often bilateral. There are patchy areas on consolidation and bronchi containing acute inflammatory exudate. There is also upper lobe emphysema.

Question 4

Lobar pneumonia

Answer 4

Characterised by diffuse inflammation affecting an entire lobe or lobes. The can see an entire lobe, paler than the other, which has become consolidated due to accumulation of acute inflammatory exudate within the alveoli. There is abrupt demarcation at the interlobar fissure.

Question 5

Consolidation

Answer 5

On a chest radiograph refers to replacement of air in alveoli by fluid or other material, with preservation of the underlying alveolar architecture. In the case of pneumonia the air is replaced by acute inflammatory exudate. here is no destruction of the underlying architecture.

Question 6

When should Abx be started in patient with pneumonia

Answer 6

Patients should commence antibiotics as soon as possible after a diagnosis of pneumonia is made, preferably within 3-4hr of presentation. This is because it is known that delay in starting antibiotics is associated with worse outcomes. However, the causative pathogen will not be known within that short time frame and so empirical antibiotic treatment is started based on the likely causative pathogens.

Question 7

CAP

Answer 7

• Strep. pneumoniae (pneumococcus) is the single commonest cause.
• Influenza and other viruses, Chlamydia pneumoniae/psittaci, Mycoplasma pneumoniae, Legionella pneumonia, Haemophilus influenzae are other causes.
• S. pneumoniae is by far the commonest cause of mild CAP.
• S. pneumoniae, Legionella and S. aureus are important causes of severe CAP.

Question 8

HAP

Answer 8

It occurs 2 days or more after admission to hospital.
Gram negative bacteria are responsible for about 60% of cases eg. Klebsiella, E. coli and Pseudomonas. S. aureus and S. pneumoniae are also important causes.

Question 9

Aspiration pneumonia

Answer 9

Pneumonia due to aspiration is particularly a risk in intoxicated patients, acute stroke patients with impaired swallowing and septic patients with reduced consciousness.
Aspiration pneumonias are omen mixed infections including anaerobes.

Question 10

Pneumonia in the immunocompromoised

Answer 10

Conventional respiratory pathogens are still common but generally the infection is more severe. In addition, they are susceptible to less virulent organisms eg.
• fungi eg. pneumocystis, Candida, Aspergillus.
• mycobacterial infection eg. M. tuberculosis or atypical mycobacteria.
• viruses eg. CMV, HSV.