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MIIM20002 - Microbes, Infections, Responses > Lecture 20 - Respiratory Tract Infections 1 > Flashcards

Lecture 20 - Respiratory Tract Infections 1 Flashcards

0
Q

What generally causes URT infections?

A

Viruses

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1
Q

What causes LRT infection?

A

Bacteria

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3
Q

Name some LRT infections

A
  • Bronchitis
  • Bronchiolitis
  • Pneumonia
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4
Q

Which viruses commonly cause URT infections?

A
  • Parainfluenza
  • Influenza
  • Respiratory syncytial virus (RSV)
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5
Q

Name some URT infections

A
  • Rhinitis
  • Pharyngitis
  • Laryngitis
  • Croup
  • Tracheitis
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6
Q

Which groups is commonly affected by pneumonia?

A

• the young
• the elderly
50% of affected people have a defect with their immune defences

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7
Q

Which agents cause pneumonia?

A

Mainly Strep. pneumoniae

  • H. influenzae
  • Klebsiella pneumoniae
  • M. tuberculosis
  • Legionella
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8
Q

What are the defences in the URT?

A

Nose: hairs, turbinates

Epiglottis: cough reflex

Respiratory epithelium: cilia, mucous, lysozyme, lactoferrin, sIgA, mucociliary elevator

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9
Q

What are turbinates?

A
  • Bone covered by mucous membrane
  • Three on each side of nose
  • Warm and humidify air
  • Filters dust, pollen, microbes
  • Turbulence; expose air to respiratory epithelium for longer
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10
Q

What are the defences in the alveoli?

A
  • sIgA
  • surfactant
  • complement
  • alveolar macrophages
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11
Q

What are the general defences in the LRT?

A
  • Alveoli
  • Blood supply
  • MALT
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12
Q

Why is a good blood supply protective in the LRT?

A

Access to:
• neutrophils
• IgG
• complement

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13
Q

What is present in the mucous of the URT?

A
  • Lysozyme
  • Lactoferrin
  • sIgA
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14
Q

What components of the innate immune system can be compromised, leading to LRT infection?

A

Defects in defences
• cough reflex
• phagocytes
• cilia

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14
Q

What is aspiration pneumonia ?

A

Breathe in the bacteria
No cough reflex when comatose
Such as in heavy drinking

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16
Q

What is aspiration pneumonia?

When does it happen?

A

Breathe in contents of URT
• Coma: no cough reflex
• Heavy drinkning

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17
Q

Where are most bacteria found in the respiratory tract?

A 
Most to least:
• Saliva
• Gingival scrapings
• Tooth surfaces
• Nose washings
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18
Q

Describe the microbiota of the lower respiratory tract

A

Sterile

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18
Q

Which organisms are commonly found in the upper respiratory tract?

A

G+ cocci

Streptococci

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19
Q

What are the symptoms of pneumonia?

A
  • Fever
  • Cough
  • Rapid respiration
  • Chest pain
  • Cyanosis
  • Chest sounds
  • Shortness of breath
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21
Q

What happens to the chest x ray in pneumonia

A

May be abnormal
• Lobar: indicates Strep. pneumoniae infection
• Non-lobar: indicates Infleunza infection

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21
Q

What do the X rays look like?

A

Normal: clear

Lobar pneumonia: upper lobe cloudy due to pus. S. pneumoniae

Non-lobar: scatter infiltrate throughout the lungs. Influenza virus

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22
Q

Describe the onset of pneumonia

A

Can be either acute or chronic

Depends on the cause

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24
Q

Where can pneumonia be acquired?

What is the difference?

A
  • Community
  • Hospital

Different organisms and modes of spread

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25
Q

How do the microbes get in?

A
  • Inhalation
  • Aspiration of URT contents in coma
  • Spread along mucous membrane surface
  • From blood
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25
Q

How is pneumonia diagnosed in a laboratory

A
  1. Specimen collected
  2. Microscopy
  3. Culture
  4. Antigen detection assay using PCR
  5. Antibody
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26
Q

How do we diagnose pneumoniae?

A

Clinical: history, examination, predisposing factors

Radiological: chest x ray

Lab

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27
Q

What do we look for in the specimen?

A

Pus cells
Bacteria

Not looking for epithelial cells –> indicates URT

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28
Q

What sort of sputum is collected

A

Sputum

Blood
Serum –> looking for antibodies

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29
Q

Why is S. pneumoniae important?

A

Most common cause of death in <5s world wide

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31
Q

Where does S. pneumoniae colonise?

A

Nasopharynx

32
Q

What is the reservoir of S. pneumoniae?

A

Humans

33
Q

Does S. pneumoniae normally cause disease

A

No

Can be part of normal flora

34
Q

When are the generalised outcomes of S. pneumoniae infection

A

Asymptomatic colonisation

Disease:
• non-invasive
• invasive

35
Q

When does S. pneumoniae cause disease?

A

When it gains access to normally sterile sites

36
Q

Do children or adults more commonly carry S. pneumoniae?

A

Children → 60%

37
Q

What is invasive disease of S. pneumoniae?

A

Spread in blood to sites:

  • Septicaemia
  • Endocarditis
  • Septic arthritis
  • Peritonitis
  • Meningitis
38
Q

What is non-invasive disease by S. pneuomniae?

A

Local disease
Spread from nasopharynx to sterile sites

  • Conjunctivitis
  • Otitis media (middle ear infection)
  • Sinusitis
  • Pneumonia
39
Q

How many serotyped of S. pneumoniae are there?
How is this bacterium typed?

What does this mean?

A

91

By its capsule

This means someone can be infected multiple times

40
Q

What is the morphology of S. pneumoniae?

A

Gram + coccus

Diplococci: in pairs

41
Q

What does naturally transform able mean?

A

Readily pick up DNA from the environment

→ resistance genes

42
Q

What are the features of S. pneumoniae?

A

Catalase negative

Facultative anaerobe

43
Q

How do we differentiate S. pneumoniae from other alpha haemolytic streptococci?

A

S. pneumoniae is susceptible to Optochin

44
Q

Which medium do we grow S. pneumoniae on?

Describe the colonies

A

Horse blood agar

Alpha haemolysis: Greening colonies

45
Q

Does S. pneumonia have a capsule?

A

The virulent ones do have a capsule

Unencapsulated S. pneumoniae can’t cause disease

46
Q

Why are the colonies of S. pneumoniae wet and shiny?

What is this called?

A

Due to the capsule

Mucoid colonies

47
Q

What are the different serotypes of S. pneumoniae?

A

The capsular polysaccharide antigens

47
Q

What is the role of the capsule

A

Masks underlying structures

Blocks complement binding

48
Q

How do we classify S. pneumoniae?

A

Serotyping

50
Q

What is the major virulence determinant of S. pneumoniae?

A

The capsule

50
Q

What does pyogenic mean?

A

Pus forming

An extracellular bacterium that evades phagocyte action

52
Q

What does pyogenic mean?

A

Pus forming

Induces phagocytes but avoids their action

53
Q

Give an overview of the Pathogenesis of S. pneumoniae

A 
Colonisation
Penetration
Replication
Evasion of immune system
Damage
Recovery / immunity
53
Q

How does the bacterium colonise?

A

Cell wall adhesins

Attach to nasopharyngeal and lung mucosa (pneumocytes)

54
Q

Are capsular antigens cross reactive?

A

No

55
Q

How does the bacterium colonise?

A

Cell wall adhesins (loads of them)

Attach to nasopharyngeal and lung mucosa (pneumocytes)

57
Q

What are NETS?

A

Neutrophil extracellular traps
Mainly made of DNA
Meshes extruded from neutrophils that trap microbes

58
Q

How does S. pneumoniae evade NETS?

A

Releases pneumococcal DNAases that break down NETS

59
Q

How does S. pneumoniae cause damage?

A
  1. Hydrogen peroxide → local tissue damage
  2. Pneumolysin
  3. Autolysins: self lyse the bacteria → more inflammation
  4. Inflammation
60
Q

What are the stages of the inflammatory response?

A
  1. Activation of endothelium → exudate
  2. Entrance of neutrophils. Ineffective, bacteria persist
  3. Neutrophils → impaired lung function, fever
  4. Resolution: macrophage action
61
Q

How do we recover?

A
  • Complement activation → phagocytosis

* Antibodies

62
Q

What are the complications of S. pneumoniae infection?

A
  1. Pleural effusion: fluid in the pleural space
  2. Dissemination:
    • Into blood and lymphatics
    • Heart
    • Meningitis
63
Q

How is complement effective against the bacterium?

A

CRP (c reactive protein) eventually triggers the cascade by binding to the cell wall

64
Q

How do we detect s. pneumoniae in the lab?

A

Growth on HBA
• greening, alpha haemolysis
• sensitivity to optochin

Serotyping

Gram stain

Capsule stain

65
Q

How is S. pneumoniae infection treated?

A

Supportive treatment:
• Bronchodilators
• Oxygen
• Analgesics

Antimicrobials:
• Cephalosporins
• Penicillins
→ however resistance

Vaccination

66
Q

Does S. pneumoniae cause pharyngtis?

A

Not normally

It is part of the normal flora and is kept in check

67
Q

What is the connection of S. pneumoniae with Australian Indigneous populations?

A

Very high incidence of invasive disease

68
Q

Describe how pneumolysin causes damage to the host

A

Released later in growth
Cytotoxic to endothelial cells (with cholesterol)
Triggers complement

69
Q

Describe how autolysins cause damage to the host

A

Induce bacterial cell death
Release cell wall components
→ Trigger complement cascade

70
Q

Describe how inflammation leads to host tissue damage

A

Inflammation sparked by pneumolysin and CRP binding to dying cells

Big inflammatory response

71
Q

Describe how inflammation leads to host tissue damage

A

Inflammation sparked by pneumolysin and CRP binding to dying cells

Big inflammatory response

72
Q

How does pneumolysin cause damage?

When is it released?

A
  • Puts pores in cells with cholesterol in the membrane (endothelium and alveolar cells)
  • Triggers complement cascade

Produced later on

73
Q

Which proinflamamatory compounds does S. pneumoniae produce?

A
  • Pneumolysin

* Autolysin

74
Q

What is pneumonia?

A

Acute inflammation of the lungs, typically, the alveoli

75
Q

What things decrease the function of the defences in the respiratory tract?

A
  • pre-existing disease (influenza)
  • smoking
  • drinking
  • anaesthesia
  • immobilisation
  • immunosuppression
  • extremes of age
76
Q

How can heavy drinking put a person a risk of LRT infection?

A

Aspiration pneumonia

• unconscious, cough reflex isn’t working

77
Q

Is Strep. pneumoniae intra- or extracellular?

A

Extracellular

MIIM20002 - Microbes, Infections, Responses (32 decks)

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