1. Respiratory Infection : Pathology of Respiratory Tract Infection Flashcards

1
Q

What are lung infections a result of?

A

An interaction between human host and an infectious agent

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2
Q

Why are lung infections considered multifactorial situations?

A

Dependent on:

  • Microorganism pathogenicity
  • Capacity to resist infection
  • Population at risk
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3
Q

What are the 3 types of microorganism pathogenicity?

A
  • 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
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4
Q

What affects a host ability to resist infection?

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

- Age of patient

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5
Q

What are examples of upper respiratory tract infections?

A
  • Coryza: common cold
  • Sore throat syndrome
  • Acute laryngotracheobronchitis: croup
  • Laryngitis
  • Sinusitis
  • Acute epiglottitis
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6
Q

What is acute epiglottitis caused by?

A
  • Group A beta-haemolytic streptococci

- Haemophilus influenza (type b -Hib)

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7
Q

What are examples of lower respiratory tract infections?

A
  • Bronchitis
  • Bronchiolitis
  • Pneumonia
  • Consequences
  • Possible complications
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8
Q

What respiratory tract defences are there?

A
  • Macrophage-mucociliary escalator skeleton
  • General immune system
  • Respiratory tract secretions
  • Upper respiratory tract acts as a filter
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9
Q

What are the 3 components of the MMES?

A
  • Alveolar macrophages
  • Mucociliary escalator
  • Cough reflex
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10
Q

What is normally sterile?

A

Lower respiratory tract

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11
Q

How are particles cleared via the MMES?

A
  • 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
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12
Q

What happens if the MMES fails?

A

Anything inhaled is retained in the lung

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13
Q

What can cause the MMES to fail?

A

Viral infection as it can lead to the loss of cilia

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14
Q

How can pneumonia be classified?

A
  • Anatomical: understand how it looks
  • Aetiological: understand the cause
  • Microbiological: understand what is appropriate for treatment
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15
Q

What are the aetiological classes of pneumonia?

A
  • Community acquired pneumonia
  • Hospital acquired pneumonia
  • Pneumonia in the immunocompromised
  • Atypical pneumonia
  • Aspiration pneumonia
  • Recurrent pneumonia
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16
Q

What are the patterns of pneumonia?

A
  • Bronchopneumonia
  • Segmental/lobar
  • Hypostatic
  • Aspiration
  • Obstructive, retention, endogenous lipid
17
Q

Hypostatic pneumonia

A

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

18
Q

How does bronchopneumonia appear?

A

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

19
Q

What happens in lobar pneumonia?

A

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

20
Q

What are the outcomes/complications of pneumonia?

A
  • Most resolve
  • Pleurisy, pleural effusion and empyema
  • Organisation
  • Lung abscess
  • Bronchiectasis
  • Potentially fatal
21
Q

What can cause a lung abscess?

A
  • Obstructed bronchus ( possibly due to tumour)
  • Aspiration
  • Particular organism
  • Metastatic in pyaemia
  • Necrotic lung as secondary infection
22
Q

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

A
  • Staph aureus
  • Some pneumococci
  • Klebsiella
23
Q

What is bronchiectasis?

A

Pathological dilatation of bronchi due to:

  • Severe infective episode
  • Recurrent infections
  • Proximal bronchial obstruction
  • Lung parenchymal destruction
24
Q

What are the symptoms of bronchiectasis?

A
  • Cough
  • Abundant purulent foul sputum
  • Haemoptysis
  • Signs of chronic infection
  • Coarse crackles
  • Clubbing
25
Q

How is bronchiectasis diagnosed?

A

-Thin section CT

26
Q

How is bronchiectasis treated?

A
  • Postural drainage,
  • Antibiotics
  • Surgery
27
Q

What can cause local bronchial obstruction?

A
  • Tumour

- Foreign body

28
Q

What can cause local pulmonary damage?

A

Bronchiectasis

29
Q

What can cause generalised lung disease?

A
  • Cystic fibrosis

- COPD

30
Q

What can cause non-respiratory disease?

A
  • Immunocompromised

- Aspiration

31
Q

What can aspiration pneumonia cause?

A
  • Vomiting
  • Oesophageal lesion
  • Neuromuscular disorders
  • Obstetric anaesthesia
  • Sedation
32
Q

What is an opportunistic infection?

A

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

33
Q

What are examples of opportunistic pathogens?

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