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
- 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
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?
- Severe pneumonia
- 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?
2) DFA= Direct fluorescent antibody detection of organisms
3) PCR (NAA or NAAT)