Legionella Flashcards

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1
Q

what is the biology of legionella pneumophila?

A
  • Small gram negative rods poorly staining*
  • Facultative intracellular *
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2
Q

inside what cell does legionella pneumophila live?

A

macrophages

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3
Q

where can we find a reservoir of legionella?

A

in water that is:

  • Parasitize protozoa in streams, rivers
  • contaminates waterlines
  • Air-conditioning cooling towers *
  • Hot water heaters *
  • Hot-tubs *
  • Grocery store produce sprayers *
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4
Q

how does legionella spread?

A

INHALATION of aerosols *

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5
Q

who is more at risk of acquiring legionella pneumophila?

A
  • Individuals over 55 yrs who smoke and drink alcohol
  • Elderly debilitated
  • Chronic lung disease, immunocompromised
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6
Q

what does legionella do Inside the phagosome?

A

Legionella uses Type 4 Secretion Systems (T4SS) to inject proteins * into the cytosol to burst the phagosomal membrane.

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7
Q

what does legionella inhibit?

A

phagolysosome fusion

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8
Q

where does legionella replicate?

A

inside vacuoles

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9
Q

what causes the host cells to be killed?

A

proteolytic enzymes produced by legionella

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10
Q

what immunity helps us combat legionella infection?

A

Immunity to disease is primarily cell mediated *(humoral immunity plays a small role)

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11
Q

what diseases does legionella cause?

A
  • Severe infection – Legionnaire’s disease*
  • Mild infection – Pontiac fever
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12
Q

who gets legionnaire’s disease?

A

Immunosuppressed patients

Smokers over 55 yrs with high alcohol intake

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13
Q

who can get Pontiac fever with legionella infection?

A

healthy individuals

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14
Q

in pontiac fever, does the disease reach the lungs?

A

there is no pulmonary involvement

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15
Q

what symptoms are seen in legionnaire’s disease?

A
  • Atypical pneumonia*
  • Acute lobar pneumonia + major confusion + diarrhea *
  • dry, NON-PRODUCTIVE COUGH*
  • Gram stain of sputum – neutrophils but no bacteria *
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16
Q

what staining techniques can be used to diagnose legionnaire’s disease?

A

since it is a poorly stain gram negative

  • DFA (direct fluorescent antibody) staining of specimens
  • Dieterle silver-stain
17
Q

what other test can be used to diagnose legionnaire’s disease?

A

Urine Antigen detection - rapid, sensitive *

18
Q

what is the treatment for legionella?

A

Macrolide – Azithromycin, clarithromycin

Newer quinolone – Levofloxacin, gatifloxacin