1. Respiratory Infection : Pathology of Respiratory Tract Infection

Question 1

What are lung infections a result of?

Answer 1

An interaction between human host and an infectious agent

Question 2

Why are lung infections considered multifactorial situations?

Answer 2

Dependent on:

• Microorganism pathogenicity
• Capacity to resist infection
• Population at risk

Question 3

What are the 3 types of microorganism pathogenicity?

Answer 3

• Primary: no matter how healthy you are, these ones will make you sick
• Opportunistic: attack the severely immunocompromised
• Facultative: need a bit of help in order to cause harm

Question 4

What affects a host ability to resist infection?

Answer 4

• The state of host defence mechanism i.e immune system

- Age of patient

Question 5

What are examples of upper respiratory tract infections?

Answer 5

• Coryza: common cold
• Sore throat syndrome
• Acute laryngotracheobronchitis: croup
• Laryngitis
• Sinusitis
• Acute epiglottitis

Question 6

What is acute epiglottitis caused by?

Answer 6

• Group A beta-haemolytic streptococci

- Haemophilus influenza (type b -Hib)

Question 7

What are examples of lower respiratory tract infections?

Answer 7

• Bronchitis
• Bronchiolitis
• Pneumonia
• Consequences
• Possible complications

Question 8

What respiratory tract defences are there?

Answer 8

• Macrophage-mucociliary escalator skeleton
• General immune system
• Respiratory tract secretions
• Upper respiratory tract acts as a filter

Question 9

What are the 3 components of the MMES?

Answer 9

• Alveolar macrophages
• Mucociliary escalator
• Cough reflex

Question 10

What is normally sterile?

Answer 10

Lower respiratory tract

Question 11

How are particles cleared via the MMES?

Answer 11

• Foreign bodies are phagocytised by macrophages. -Macrophages migrate towards the cilia.
• The cilia beat up and outwards
• Digestions of foreign bodies get trapped in the mucous which is swept up the respiratory tract by the cilia and coughed out or swallowed.
• Alternatively macrophages take the interstitial pathway via the lymph to the lymph nodes

Question 12

What happens if the MMES fails?

Answer 12

Anything inhaled is retained in the lung

Question 13

What can cause the MMES to fail?

Answer 13

Viral infection as it can lead to the loss of cilia

Question 14

How can pneumonia be classified?

Answer 14

• Anatomical: understand how it looks
• Aetiological: understand the cause
• Microbiological: understand what is appropriate for treatment

Question 15

What are the aetiological classes of pneumonia?

Answer 15

• Community acquired pneumonia
• Hospital acquired pneumonia
• Pneumonia in the immunocompromised
• Atypical pneumonia
• Aspiration pneumonia
• Recurrent pneumonia

Question 16

What are the patterns of pneumonia?

Answer 16

• Bronchopneumonia
• Segmental/lobar
• Hypostatic
• Aspiration
• Obstructive, retention, endogenous lipid

Question 17

Hypostatic pneumonia

Answer 17

Pneumonia due to bacterial growth in lung where there is a collection of secretions due to lack of draining

Question 18

How does bronchopneumonia appear?

Answer 18

Often bilateral basal patchy opacification, relating to the focal nature of the consolidation

Question 19

What happens in lobar pneumonia?

Answer 19

It is more invasive and aggressive. Organisms are washed throughout the lung until it reaches the pleura where it can go no further

Question 20

What are the outcomes/complications of pneumonia?

Answer 20

• Most resolve
• Pleurisy, pleural effusion and empyema
• Organisation
• Lung abscess
• Bronchiectasis
• Potentially fatal

Question 21

What can cause a lung abscess?

Answer 21

• Obstructed bronchus ( possibly due to tumour)
• Aspiration
• Particular organism
• Metastatic in pyaemia
• Necrotic lung as secondary infection

Question 22

What organisms are likely to be involved in the formation of an abscess?

Answer 22

• Staph aureus
• Some pneumococci
• Klebsiella

Question 23

What is bronchiectasis?

Answer 23

Pathological dilatation of bronchi due to:

• Severe infective episode
• Recurrent infections
• Proximal bronchial obstruction
• Lung parenchymal destruction

Question 24

What are the symptoms of bronchiectasis?

Answer 24

• Cough
• Abundant purulent foul sputum
• Haemoptysis
• Signs of chronic infection
• Coarse crackles
• Clubbing

Question 25

How is bronchiectasis diagnosed?

Answer 25

-Thin section CT

Question 26

How is bronchiectasis treated?

Answer 26

• Postural drainage,
• Antibiotics
• Surgery

Question 27

What can cause local bronchial obstruction?

Answer 27

• Tumour

- Foreign body

Question 28

What can cause local pulmonary damage?

Answer 28

Bronchiectasis

Question 29

What can cause generalised lung disease?

Answer 29

• Cystic fibrosis

- COPD

Question 30

What can cause non-respiratory disease?

Answer 30

• Immunocompromised

- Aspiration

Question 31

What can aspiration pneumonia cause?

Answer 31

• Vomiting
• Oesophageal lesion
• Neuromuscular disorders
• Obstetric anaesthesia
• Sedation

Question 32

What is an opportunistic infection?

Answer 32

Infection by organisms not normally capable of producing disease in patients with intact lung defences

Question 33

What are examples of opportunistic pathogens?

Answer 33

• Low grade bacterial pathogens
• CMV
• Pneumocystitis jirovecii
• Other fungi and yeasts