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Microbiology Exam 2 > 29 - Bacterial Infections of the Lower Respiratory Tract II > Flashcards

29 - Bacterial Infections of the Lower Respiratory Tract II Flashcards

1
Q

Recall type of CXR pattern we will see in atypical pneumonia…

A

Patchy pattern

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2
Q

What are the causative agents we see in atypical pneumonia?

A

TWO MAIN

  • Mycoplasma pneumoniae
  • Chlamydophila pneumoniae

Others

  • Chlamydophila psittaci
  • Coxiella burnettii
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3
Q

The difference between lobar (typical) and bronchopneumonia (atypical) is the amount of _________ seen in the lungs.

A

Fluid

Among other differences…

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4
Q

What is a common name for atypical pneumonia?

A

Walking pneumonia

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5
Q

How will patients with walking pneumonia present differently

A
  • They will present looking a lot better than their labs will show
  • They might have a cough, but otherwise pretty good
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6
Q

What is the one causative agent in toxic pneumonia?

A

Legionella pneumophila

* a special case*

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7
Q

What are the symptoms you will see with atypical pneumonia?

A
  • Bronchopneumonia with gradual onset
  • Fever, headache, fatigue, muscle ache, dry cough with scant/watery sputum
  • Cough started a couple weeks ago, still getting worse
  • No rust-colored sputum
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8
Q

How do you treat atypical pneumonia?

A
  • Tetracycline and erythromycin

Usually, if someone comes in with walking pneumonia, you won’t have to do a lot, just give them these and send them on their way

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9
Q

What are mycoplasma pneumoniae?

A

The smallest free living bacteria, pleomorphic

Causative agent of atypical pneumonia

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10
Q

What are some characteristics of mycoplasma pneumoniae?

A
  • No peptidoglycan! *

- Membrane contains sterols (Steals cholesterol from humans for this)

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11
Q

Does mycoplasma pneumoniae require a host?

A

Yes

  • Requires supplementation with sterols and nucleotide precursors
  • Can’t make everything it needs, so it requires a host
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12
Q

What does the “fried egg” morphology mean?

A

Colony of bacteria is thin, but then there is a “yolk” looking bump in the middle of the colony

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13
Q

What species will you find mycoplasma pneumoniae living in?

A

Restricted to humans

Some strains are part of the normal oral microbiota

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14
Q

How do you transmit mycoplasma pneumoniae?

A

Respiratory droplets

A very low infectious dose is required for transmission to cause tracheobronchitis

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15
Q

How many cases of mycoplasma pneumoniae do we see in the US each year?

A

2 million

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16
Q

What is the main virulence factor for mycoplasma pneumoniae?

A

P1 adhesion

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17
Q

How does the P1 adhesin virulence factor work?

A
  • Binds to base of cilia
  • Ciliostasis
  • Epithelial cell damage/death
  • Defect in mucociliary clearance

IMPORTANT

Causes the majority of symptoms

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18
Q

What does the loss of the mucociliary clearance lead to?

A
  • Mucous/fluid accumulation in the lungs

- Pneumonia

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19
Q

What are the symptoms of mycoplasma pneumonia causing pneumonia?

A
  • Bronchopneumonia with gradual onset
  • Fever, headache, fatigue, muscle ache, dry cough with scant/watery sputum
  • Anemia *
  • IgM response cross reacting with RBC (resulting in anemia)
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20
Q

What type of CXR will you see with mycoplasma pneumoniae?

A

Patchy infiltrates

following the bronchioli, bronchioles and some of the alveoli

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21
Q

How do you diagnose mycoplasma pneumoniae?

A
  • Cold Agglutinin Test
  • PCR
  • Serology

Microscope/culture NOT recommended (too small)

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22
Q

What is the cold agglutinin test?

A

Agglutinate = “firmly stick together”

  • RBCs agglutinate at 4 degrees C, not 37 degrees C (body temp)
  • This is a nonspecific IgM reaction
  • 50-75% of patients with mycoplasma pneumoniae will be positive 1-2 weeks after infection
  • Utility of this test has been questioned
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23
Q

What is the benefit of using a PCR to detect mycoplasma pneumoniae?

A
  • high sensitivity
  • specificity improving
  • now commercially available
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24
Q

What is the benefit of using serology to detect mycoplasma pneumoniae?

A

These are enzyme immunoassays (EIA)

  • Common
  • Commercially available
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25
How do you treat mycoplasma pneumoniae?
Tetracycline and macrolide (erythromycin) This is the emperical therapy for atypical pneumonia that we use in the absence of signs of pneumococcal pneumonia
26
Why don't we use beta lactams to treat mycoplasma pneumoniae? *****
IMPORTANT There is NO peptidoglycan in mycoplasma pneumonia, meaning there is NO target for the beta lactams *********
27
Will mycoplasma pneumoniae resolve on its own?
Yes, the disease generally is self-limiting (2 weeks)
28
What percentage of all bacterial pneumonias are due to mycoplasma pneumoniae?
20% - a large portion
29
What symptoms will you see in mycoplasma pneumoniae?
Similar to other pneumonias | - really hard to distinguish between cases by clinical presentation alone
30
What other diseases present very similar to mycoplasma pneumoniae?
Similar to... - chlamydophilia - adenovirus 3 and 4 - influenza A or B - RSV
31
How do you prevent mycoplasma pneumoniae?
No prevention really... Just avoid overcrowded areas
32
What is chlaymodphilia pneumoniae?
Another type of bacteria that causes walking (atypical) pneumonia
33
What type of bacteria is chlaymodphilia pneumoniae?
Small gram negative bacteria Obligate intracellular pathogen
34
How many cases to we see of chlaymodphilia pneumoniae?
- Estimates of cases vary widely - Hard to get ahold of these stats - We don’t always get these information
35
What other diseases are associated with the development of chlaymodphilia pneumoniae?
The pathogen has recently been associated with: - atherosclerotic plaque formation - asthma - multiple sclerosis - rheumatoid arthritis
36
How do you diagnose chlaymodphilia pneumoniae?
1 - Microimmuofluorescence (test for anti-Chlamydophila antibody) 2 - PCR detection (assay cleared by FDA in 2012 - not sure if it widely used yet)
37
How do you treat chlaymodphilia pneumoniae?
Tetracycline and a macrolide | same as M. pneumoniae
38
How do chlaymodphilia pneumoniae replicate?
Binary fission - a form of asexual reproduction and cell division used by all prokaryotes Using ATP from host cell (they are energy parasites that can't make their own energy)
39
What is Legionella pneumophila?
The causative agent of Legionnaires’ disease, a respiratory disease, which had its first outbreak at the Legion convention in Philadelphia in 1976 where there were 182 cases and 29 deaths
40
Why did so many veterans contract and die from Legionella pneumophila? *******
COPD predisposed them... Lifetime spokers, older men, chronic bronchitis, emphysema ************
41
What else does Legionella pneumophila cause?
Pontiac fever and pneumonia
42
What type of a bacteria is Legionella pneumophila?
- Gram negative coccobacilli | - When it is outside of cells (in the lab culture) it will become pleomorphic (some rods, some cones)
43
Why is Legionella pneumophila difficult to culture?
- Slow growth( > 3 days) - Fastidious (needs a complex media of charcoal yeast agar) - Needs high humidity (90%)
44
Due to the fact that we see it growing well in areas of high humidity, where will we find it in nautre?
This is why we see it in streams, lakes, potting soil, snow banks, mud
45
What type of parasites are Legionella pneumophila?
Parasites that live mostly inside of amoeba cells, which protect them from the outside environment
46
How do Legionella pneumophila get transferred to humans?
Aerosols from manmade water supplies that harbor Legionella and their amoeba host (The steam machine in front of the school, for example)
47
What are outbreaks of Legionella pneumophila associated with?
- Cooling towers and air conditioning systems of large buildings like hotels, factories, hospitals - Respiratory therapy devices (humidifiers, nebulizers) - Less common in hot water from faucet, shower heads and Supermarket produce misting systems
48
What is the pathogenic mechanism of Legionella pneumophila?
- Target and attach to alveolar macrophage using pili, flagella, numerous proteins - Induces its own uptake - Enter macrophage in a endocytic vacuole - Coiling phenomenon is then observed (unique phenomenon – don’t know why)
49
What does the Legionella pneumophila do once its inside the cell?
Hijacks the cell and replicates
50
What are the steps in this hijack and replication?
- Hundreds of bacterial proteins are injected into the cytosol - Prevents fusion with lysosome (so they don’t get acidification) - Recruits ribosomes, mitochondria, ER to the vacuole now called the Legionella-containing vacuole (LCV) -- It has set up shop in the vacuole - Replication of bacteria to high numbers cell lyses and the process starts over again
51
How is the bacteria replication detrimental to tissues?
``` Multiple bacterial and host enzymes are release in this process and you will see... - Inflammation - Lung necrosis - Systemic toxicity ```
52
Why do we call pneumonia from legionella pneumonia a toxic pneumonia?
Because of the systemic toxicity it has when it is replicating, releasing toxic material, killing lung tissue, and spreading to the blood (systemic toxicity)
53
What are some symptoms of severe toxic pneumonia?
- Myalgia, headache, rapidly rising fever - Dry cough, may become productive - Chills, pleurisy, vomiting, diarrhea, confusion, delirium
54
What will we see on a CXR of a patient with toxic pneumonia?
Patchy infiltrates on CXR
55
What will lab values indicate in a patient with toxic pneumonia?
Elevated WBC count
56
What is the typical disease progression in severe toxic pneumonia?
Patient becomes progressively ill over 3-6 days and results in shock, respiratory failure or both
57
How do you test for legionella pneumoniae causing toxin pneumonia?
- Culture - Direct flourescent antibody (DFA) - Nucleic acid amplification test (NAAT)
58
What is the Direct flourescent antibody (DFA) test?
- You take a sample from lung aspirate, bronchoalveolar lavage, or a biopsy - Downfall is that it is only positive in 25-50% of patients that have it
59
What is the NAAT test?
Nucleic acid amplification test (NAAT) - a PCR test for detecting Legionella DNA in respiratory specimen - You could get a false negative due to PCR inhibitors in the secretions - Typically you will culture and do a NAAT
60
How do you treat toxic pneumonia?
Macrolide or a fluoroquinolone is preferred
61
Can you use beta lactams?
NO
62
Why can't you use beta lactams?
Most isolates produce beta-lactamases to break down the drug
63
How do you prevent toxic pneumonia?
Minimizing exposure to / production of contaminated aerosols

Microbiology Exam 2 (8 decks)

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