Exam #4: Lower Respiratory Tract Infections II

Question 1

What bacteria cause atypical bacterial pneumonia?

Answer 1

• Mycoplasma Pneumoniae
• Chlamydophila pneumoniae
• *Legionella pneumophila

Question 2

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

Answer 2

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

Question 3

What are the symptoms of bronchopneumonia or atypical pneumonia?

Answer 3

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

Question 4

How is atypical pneumonia treated?

Answer 4

Tetracycline & erythromycin

Question 5

List the characterstics of Mycoplasma pneumoniae.

Answer 5

• 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

Question 6

What virulence factor is associated with mycoplasma pneumoniae?

Answer 6

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

Question 7

Why is anemia associated with mcyoplasma pneumoniae infection?

Answer 7

IgM response cross reacting with RBC can lead to anemia

Question 8

How is mycoplasma pneumoniae diagnosed?

Answer 8

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

Question 9

How is mycoplasma pneumoniae treated?

Answer 9

• Tetracycline & macrolide (erythromycin)

- NOT beta-lactams because NO peptidogylcan

Question 10

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

Answer 10

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

Question 11

How is Chlamydophila pneumoniae diagnosed?

Answer 11

• Microimmunofluorescence (antibody)

- PCR detection

Question 12

How is Chlamydophila pneumoniae treated?

Answer 12

Tetracycline & a macrolide (erythromycin)

Question 13

What is Legionella pneumophila?

Answer 13

Causative agent of Legionnaires Disease

Question 14

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

Answer 14

Legionnares Disease=

• Severe pneumonia
• Fever
• GI symptoms
• CNS symptoms

Pontiac Fever= mild flu like illness

Question 15

How do Legionnares Disease & Pontiac Fever differ?

Answer 15

Legionnares Disease= much less prevalent but much more severe

Pontiac Fever= much more prevalent but also much less severe

Question 16

List the characteristics of Legionella pneumophila.

Answer 16

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

Question 17

How is Legionella pneumophila transmitted to humans?

Answer 17

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

Question 18

What are Legionella pneumophila outbreaks associated with?

Answer 18

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

Question 19

Describe the virulence & pathogenesis of Legionella pneumophila.

Answer 19

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

Question 20

How does Legionella pneumophila hijack the cell?

Answer 20

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

Question 21

What is an LCV?

Answer 21

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

Question 22

How does Legionella pneumophila infection manifest clinically?

Answer 22

• 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)

Question 23

How is Legionella pneumophila infection diagnosed?

Answer 23

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

Question 24

How is Legionella pneumophila treated?

Answer 24

• NOT beta-lactams (most isolates produce beta-lactamases)

- Currently a macrolide or fluoroquinolone is preferred