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BLOCK B - RESPIRATION > Pneumonia (infectious) > Flashcards

Pneumonia (infectious) Flashcards

1
Q

In this lecture, pneumonia refers to…

A

Infection of the lung by a microbe, typically involving the alveolar space and parenchyma.

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2
Q

How is pneumonia typically diagnosed?

A

CXR findings and clinically compatible syndrome (set of symptoms)

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3
Q

How can pneumonia be classified (4)

A
  1. Community acquired (CAP) vs Hospital acquired (HAP)
    * This is the most commonly used distinction
  2. Organisms
    * Bacterial, viral, typical vs atypical pathogens
  3. Pathogenesis
    * Aspiration, ventilator-associated
  4. Anatomic distribution
    * Lobar vs multifocal bronchopneumonia vs interstitial
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4
Q

What is the most common infectious cause of death in North America?

A

Pneumonia

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5
Q

What is the most important cause of death in children under 5 in developing countries?

A

Pneumonia

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6
Q

What are the possible bacterial sources of pneumonia?

A

Usually, our lungs should be relatively microbe-free. However, bacteria can reach the lungs by…
* inhalation (bacteria and virus)
* aspiration of oropharyngeal contents (bacteria)
* direct extension (virus and bacteria travel down the airways and affect the alveolar spaces)
* hematogenous spread (bacteria)
* exogenous contamination (because alveolar wall is disrupted by trauma - eg. catheter insertion)

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7
Q

Why is it that the defences that usually prevent us from developing an infection fail and lead to pneumonia?

A
  • Defect on host defences
  • Overwhelming bacterial inoculum (eg. in the case of aspiration)
  • Highly virulent microorganism
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8
Q

What are the host defences that protect our lungs from microorganisms?

A
  1. Nasopharynx, vocal cords and OP barrier
    * Mucus and nose hairs trap particles
    * Reflex for glottis closure when eating (prevents aspiration of food)
  2. Mucociliary escalator
    * On the surface of the respiratory epithelium, mucus traps particles and is moved upwards to clear bacteria and other foreign agents
  3. Lung immune cells
    * Macrophages in the alveolar space digest foreign agents and activated the immune system
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9
Q

In what conditions are the immune defences of our airways/lungs compromised?

A
  • Disruption of glottis reflex, aspiration, abnormal OP
  • Ciliary dyskinesia
  • Bronchiectasis
  • Cystic fibrosis
  • Endotracheal tube
  • Trauma
  • Viral co-infection (viral infection can predipose and facilitate bacterial infection)
  • Smoking (squamous cell metaplasia)
  • HIV (or other immunocompromised conditions)
  • Immune suppressive medications (including chemotherapy)
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10
Q

What are the 3 microbiological causes of pneumonia (microorganisms)

A

Bacteria, viruses and fungi

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11
Q

How are pneumonia-inducing bacteria characterized?

A
  1. Typical (eg. streptococcus pneumoniae) vs Atypical (eg. mycoplasma pneumoniae)
  2. Selected populations (very specific types of populations will be at risk for these organisms)
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12
Q

Why is understanding the microbiology of pneumonia important?

A

The microbiology determines the antibiotic of choice for treatment!

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13
Q

What demographic is most commonly affected by CAP?

A

Children and especially the elderly

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14
Q

What organisms are responsible for CAP in children, adults, and the elderly?

A

Children: respiratory viruses
Young adults: atypical bacteria
Elderly: S. pneumoniae

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15
Q

The organisms causing HAP will be different for people with … vs …

A

will be different for people with a normal immune system and immunocompromised individuals

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16
Q

What organisms are responsible for HAP in individuals with normal immune systems vs immune-compromised individuals?

A

Normal immune system: anaerobic infections

Immune-compromised: opportunistic bacteria, fungal infections, more drug-resistant organisms

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17
Q

Takeaway: What is the most common microbiological cause for CAP vs HAP?

A

CAP: viruses and atypical bacteria, streptococcus pneumoniae
HAP: Streptococcus pneumoniae is still common, but other organisms become problematic like S. aureus, gram-negative bacteria, anaerobes, opportunistic infections

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18
Q

What organism most commonly causes bacterial pneumonia? Describe some key facts (3) (CAP vs HAP, colonization, susceptible hosts)

A

Streptococcus pneumoniae
* 90% is CAP, but is still the most common cause of HAP
* can colonize the oropharynx without causing pneumonia
* susceptible hosts: young children, elderly, smokers, alcohol abuse, post-influenza

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19
Q

Strep. pneumoniae is
a) gram-positive
b) gram-negative

A

a) gram positive

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20
Q

Pathology of Strep. pneumoniae:
Inflammatory edema fills the alveolar airspace and spreads between the alveoli through…

A

the pores of Kohn
(airspace (lobar) pneumonia)

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21
Q

What are some clinical signs of Strep. pneumoniae

A

Acute onset, high fever, shaking, chills, pleuritic chest pain, rust coloured sputum (pretty typical of most pneumonia)

CXR: lobar pneumonia, air bronchograms

*Make sure you can recognize pneumonia on a CXR

22
Q

What are some possible complications of Strep. pneumoniae?

A

Empyema, bacteremia

23
Q

How does Strep. pneumoniae repsond to treatment?

A

Rapid response to treatment

24
Q

What is the most common atypical organism that can cause pneumonia?

A

Mycoplasma pneumoniae

25
Q

What is “atypical” about mycoplasma pneumoniae in terms of the symptoms it causes

A

Cause mild “walking pneumonia
Symptoms resemble more viral infections (headache, sore throat, myalgia)

26
Q

Why is mycoplasma pneumoniae only susceptible to select antibiotics? What about it is different from most bacteria?

A

This bacterium has no cell wall

27
Q

What is the pattern created by mycoplasma pneumonia on CXR and CT?

A

CXR: Interstitial pattern (diffused lines and dots)
CT scan: Ground glass opacities and nodules

28
Q

Staphylococcus aureus usually affects…

A

select populations

29
Q

Staphylococcus aureus is
a) gram positive
b) gram negative

A

a) gram positive

30
Q

Explain “MSSA vs MRSA”

A

??

31
Q

How is staphylococcus usually acquired?

A

Primarily hospital acquired

32
Q

What are the susceptible hosts of staphylococcus?

A

Post-influenza patients (bacterial superinfection), elderly, children

33
Q

35-50% of the general population is colonized by staphylococcus without developing a disease!! However, most of us are not affected. How come?

A

This bacterium causes bacterial superinfection in post-influenza patients and affects individuals with vulnerable immune systems:
* young children
* elderly
* post-influenza patients

34
Q

Describe the pathology of staphylococcus

A

The bacterium spreads rapidly and can cause necrosis and cavitation, tissue destruction, empyema, abscess

35
Q

What is the most common CXR pattern of staphylococcus?

A

Broncho-pneumonia
Frequently involves multiple lobes

36
Q

Name a gram-negative, usually hospital acquired bacterium

A

Pseudomonas aeruginosa

37
Q

Susceptible hosts of Pseudomonas aeruginosa

A

Patients with underlying lung disease (e.g. COPD, CF), immunocompromised

38
Q

Pseudomonas aeruginosa resembles a lot of other pneumonias in terms of symptoms and clinical presentation. Why is it important to recognize?

A

Because it is not covered by many antibiotics and has a high risk of resistance

39
Q

Name two important viruses that can cause pneumonia

A

Influenza
Sars-CoV-2

40
Q

Influenza is an important cause of death, particularly in…

A

the elderly

41
Q

What are 2 complications of influenza pneumonia?

A

Bacterial superinfection
Acute respiratory distress syndrome

42
Q

What would you see in viral infection lab tests (influenza pneumonia)

A
43
Q

On CXR, viral (influenza) pneumonia typically resembles…

A

atypical bacterial pneumonia.

*There is no specific pattern

44
Q

What is aspiration pneumonia?

A

Pneumonia acquired by aspiration, i.e.

45
Q

Who is at risk of aspiration pneumonia?

A

Elderly, altered mental status, alcoholism, neurological deficits, vomiting

46
Q

Describe the 2 most common categories of bacteria involved in aspiration pneumonia?

A

Gram negative bacteria and anaerobes, often polymicrobial

47
Q

What is a typical clinical characteristic of aspiration pneumonia?

A

Foul smelling or tasting sputum

48
Q

What are certain CXR patterns of aspiration pneumonia?

A

???

49
Q

What is the key to diagnosis and evaluation of pneumonia?

A

CXR

50
Q

What are some forms of prevention for pneumonia?

A
  • Vaccination
  • Smoking cessation
  • Limiting person to person transmission
  • Aspiration prevention

BLOCK B - RESPIRATION (31 decks)

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