Exam #4: Lower Respiratory Tract Infections II Flashcards Preview

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

What bacteria cause atypical bacterial pneumonia?

- Mycoplasma Pneumoniae
- Chlamydophila pneumoniae
- *Legionella pneumophila


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


What are the symptoms of bronchopneumonia or atypical pneumonia?

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


How is atypical pneumonia treated?

Tetracycline & erythromycin


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


What virulence factor is associated with mycoplasma pneumoniae?

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


Why is anemia associated with mcyoplasma pneumoniae infection?

IgM response cross reacting with RBC can lead to anemia


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


How is mycoplasma pneumoniae treated?

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


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


How is Chlamydophila pneumoniae diagnosed?

- Microimmunofluorescence (antibody)
- PCR detection


How is Chlamydophila pneumoniae treated?

Tetracycline & a macrolide (erythromycin)


What is Legionella pneumophila?

Causative agent of Legionnaires Disease


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


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


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


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


What are Legionella pneumophila outbreaks associated with?

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


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


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


What is an LCV?

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


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)


How is Legionella pneumophila infection diagnosed?

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


How is Legionella pneumophila treated?

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

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