Exam #4: Lower Respiratory Tract Infections II Flashcards Preview

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Flashcards in Exam #4: Lower Respiratory Tract Infections II Deck (24):
1

What bacteria cause atypical bacterial pneumonia?

- Mycoplasma Pneumoniae
- Chlamydophila pneumoniae
- *Legionella pneumophila

2

What is the difference between walking pneumonia & toxic pneumonia? What bacteria cause these two different forms of pneumonia?

Walking pneumonia= patient looks better on presentation than is indicative of their CXR
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae

Toxic pneumonia= very severe disease caused by Legionella pneumophila

3

What are the symptoms of bronchopneumonia or atypical pneumonia?

- Gradual onset of symptoms
- Fever
- Headache
- Fatigue
- Myalgia
- Dry cough
- Scant/watery sputum

4

How is atypical pneumonia treated?

Tetracycline & erythromycin

5

List the characterstics of Mycoplasma pneumoniae.

- Smallest free living bacteria
- Pleomorphic (no distinguishable shape)
- No peptidoglycan!
- Membrane contains sterols
- Culture requires supplementation with sterols & nucleotide precursors
- Fried egg colony morphology
- Restricted to humans
- Low infectious dose

*Some strains are part of the normal oral microbiota

6

What virulence factor is associated with mycoplasma pneumoniae?

P1 Adhesin that binds cilia & leads to ciliostasis, epithelial cell death/damage, & defect in mucociliary clearance

7

Why is anemia associated with mcyoplasma pneumoniae infection?

IgM response cross reacting with RBC can lead to anemia

8

How is mycoplasma pneumoniae diagnosed?

1) Microscopy i.e. culture is NOT recommended because of the small cell size & slow growth rate
2) Cold Agglutinin Test
3) PCR specific to mycoplasma
4) Serology

9

How is mycoplasma pneumoniae treated?

- Tetracycline & macrolide (erythromycin)
- NOT beta-lactams because NO peptidogylcan

10

List the characteristics of Chlamydophila pneumoniae. Aside from pneumonia, what else is C. penumoniae associated with?

- Small Gram (-) obliagte intracellular pathogen
- Cause atypical pneumonia
- Implicated in atherosclerotic plaque formation

11

How is Chlamydophila pneumoniae diagnosed?

- Microimmunofluorescence (antibody)
- PCR detection

12

How is Chlamydophila pneumoniae treated?

Tetracycline & a macrolide (erythromycin)

13

What is Legionella pneumophila?

Causative agent of Legionnaires Disease

14

What are the two types of disease that Legionella pneumophila causes in humans?

Legionnares Disease=
- Severe pneumonia
- Fever
- GI symptoms
- CNS symptoms

Pontiac Fever= mild flu like illness

15

How do Legionnares Disease & Pontiac Fever differ?

Legionnares Disease= much less prevalent but much more severe

Pontiac Fever= much more prevalent but also much less severe

16

List the characteristics of Legionella pneumophila.

- Gram (-) coccobacilli
- Difficult to culture (silver stain)
- Ubiquitous in aquatic environments & requires high humidity
- Mainly exists as parasites of amoeba

17

How is Legionella pneumophila transmitted to humans?

Aerosols from manmade water supplies that harbor Legionella & their amoeba host
- I.e. cooling towers & air conditioning units in old hotels, factories, & hospitals
- Respiratory therapy devices

18

What are Legionella pneumophila outbreaks associated with?

- Cooling towers & air conditioning units in old hotels, factories, & hospitals
- Resp. therapy device

19

Describe the virulence & pathogenesis of Legionella pneumophila.

- Target & attach to alveolar macrophages using pili, flagella, & numerous proteins
- Enter macrophage via endocytic vacuole--called the coiling phenomenon
- Hijacks the cell

20

How does Legionella pneumophila hijack the cell?

1) 100s of bacterial proteins are injected into the cell using a type 4 secretion system, preventing fusion with the lysosome
2) Recruits ribosome, mitochondria, & ER to the Legionella-containing vacuole
3) Replication of bacteria to high numbers
4) Cell lysis
5) Multiple bacterial & host enzymes are released in this process, which leads to inflammation, lung necrosis, and systemic toxicity

21

What is an LCV?

A vacuole containing Legionella that has recruited the ribosome, mitochondria, & ER

22

How does Legionella pneumophila infection manifest clinically?

- Severe toxic pneumonia
- Myalgia, headache, rapidly rising fever
- Dry cough, may be productive
- Chills, pleurisy, vomiting, diarrhea, confusion
- Patchy infiltrate on CXR
- Patient becomes progressively ill over the course of 3-6 days-->shock, resp. failure
- Elevated WBC count (leukocytosis)

23

How is Legionella pneumophila infection diagnosed?

1) Culture
2) DFA= Direct fluorescent antibody detection of organisms
3) PCR (NAA or NAAT)

24

How is Legionella pneumophila treated?

- NOT beta-lactams (most isolates produce beta-lactamases)
- Currently a macrolide or fluoroquinolone is preferred

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