Legionella

Question 1

what is the biology of legionella pneumophila?

Answer 1

• Small gram negative rods poorly staining*
• Facultative intracellular *

Question 2

inside what cell does legionella pneumophila live?

Answer 2

macrophages

Question 3

where can we find a reservoir of legionella?

Answer 3

in water that is:

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

Question 4

how does legionella spread?

Answer 4

INHALATION of aerosols *

Question 5

who is more at risk of acquiring legionella pneumophila?

Answer 5

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

Question 6

what does legionella do Inside the phagosome?

Answer 6

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

Question 7

what does legionella inhibit?

Answer 7

phagolysosome fusion

Question 8

where does legionella replicate?

Answer 8

inside vacuoles

Question 9

what causes the host cells to be killed?

Answer 9

proteolytic enzymes produced by legionella

Question 10

what immunity helps us combat legionella infection?

Answer 10

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

Question 11

what diseases does legionella cause?

Answer 11

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

Question 12

who gets legionnaire’s disease?

Answer 12

Immunosuppressed patients

Smokers over 55 yrs with high alcohol intake

Question 13

who can get Pontiac fever with legionella infection?

Answer 13

healthy individuals

Question 14

in pontiac fever, does the disease reach the lungs?

Answer 14

there is no pulmonary involvement

Question 15

what symptoms are seen in legionnaire’s disease?

Answer 15

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

Question 16

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

Answer 16

since it is a poorly stain gram negative

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

Question 17

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

Answer 17

Urine Antigen detection - rapid, sensitive *

Question 18

what is the treatment for legionella?

Answer 18

Macrolide – Azithromycin, clarithromycin

Newer quinolone – Levofloxacin, gatifloxacin