Legionella Pneumophila causing Legionnaires disease

Question 1

morphology

Answer 1

gm negative bacilli; obligate or facultative intracellular

Question 2

extracellular or intracellular obligate

Answer 2

intracellular obligate

Question 3

patient presentation

Answer 3

malaise, fever, worsening nonproductive cough, SOB, altered sensorium, tachycardic, rest acidosis, no travel history

multilobar infiltrates on CXR

Question 4

Lab blood test results !!

Answer 4

high WBC

increased ferritin (binds and sequesters iron to inhibit microbial iron scavenging)

decreased electrolytes (Na+ and phosphate)

Increased liver enzymes (AST ALT)

increased ESR and CRP

Question 5

Lab staining

Answer 5

Dieterle silver stain

Gram stain of BAL demonstrates polymorphonuclear leukocytes (PMNL), no organisms

Direct Fluorescent-Antibody Staining (DFA) is positive

Question 6

Lab culture

Answer 6

Buffered Charcoal yeast extract BCYE - cistern iron agar

demonstrates black with silver light bluish colonies

Question 7

complications

Answer 7

altered mental status!! , neurological symptoms also including lethargy, and headache and nonsocial neurological exam findings

rest failure,
pneumonia bilaterally,
rapid worsening of pulmonary infiltrates

Question 8

treatment

Answer 8

antimicrobials that can penetrates WBC: azithromycin
Fluroquinolones- Levofloxacin/Cirprofloxacin

Beta lactams not preferred- will no penetrate and organism produces betalactamase

Question 9

path

Answer 9

alveolar macrophages take up microbes; prevented phagosome lysosomal fusion and therefore intracellular replication commences

T cells stimulate increase antimicrobial activity which halt intracellular growth

TNF alpha is released as macrophage defense causing reduced organism replication and reduced iron (increased ferritin) which is required by the bacteria