5- Legionnaires

Question 1

what is the most common manifestation of legionnaires disease

Answer 1

pneumonia

Question 2

what two conditions can legionella cause

Answer 2

• Legionnaires diseases

- Pontiac fever (self limiting acute febrile illness)

Question 3

rare extrapulmonary manifestations of legionella

Answer 3

cellulitis, abscesses, endocarditis, meningitis

Question 4

T/F pneumonia caused by legionella is clinically and radiographically similar to other forms of pnuemonia

Answer 4

T

Question 5

common symptoms of legionnaires

Answer 5

fever, cough, dyspnea, (fever and fatigue before cough), rales and signs of consolidation on physical exam (patchy unilobular infiltrates which progress to consolidations)

Question 6

How is legionella obtained

Answer 6

through exposure to contaminated water or soil

Question 7

signs that make you thing of legionnaires pneumonia and not CAP

Answer 7

• nausea, vomiting, diarrhea
• hyponatremia
• elevated hepatic transaminases
• CRP >100 Mg/L
• failure to respond to treatment of pneumonia with B lactams

Question 8

mortality of legionnaires disease is

Answer 8

1-10%

Question 9

local complications of legionnares are

Answer 9

empyema and lung abscess

Question 10

T/F clinical features of legionnaires disease do not appear to vary with the infecting species or serotypes

Answer 10

T

Question 11

Differences between the two species of legionnaires bacteria

Answer 11

L. pneumophilia: is found worldwide, and is acquired from contaminated water sources in late summer and early fall
L. longbeachae: has more restricted geographical location (australia, new zealand), is acquired from soil in late spring and early summer

Question 12

T/F legionella infection occur sporadically in pts with CAP

Answer 12

T

Question 13

T/F lab testing is necessary for diagnosis of legionnaires

Answer 13

T

Question 14

who to test for legionella

Answer 14

an inclusive approach is taken

• all pts with mod/sev CAP or those that need hospitalisation
• any pt with CAP or nosocomila penumonia who has known exposure to legionella
• immunocompromised pts

Question 15

tests for dx of legionella infection

Answer 15

nucleic acid detection (PCR)
urine antigen tests***
culture

Question 16

T/F sensitivity of urine antigen tests ranges from 70-80%, and specificity approaches 100% in pts with legionnaires due to L. pneumophilia serotype 1

Answer 16

T

Question 17

T/F legionella antigens can be found in urine one day after symptom onset and persist for days to weeks

Answer 17

T (the turnaround time for the assay is a few hours)

Question 18

major disadvantage of urine antigen assay in legionella

Answer 18

it only detects L. pneumophilia serotype 1 (this causes 80% of cases in most of the world apart from australia)

Question 19

symptoms of pontiac fever

Answer 19

non specific, fever, headache, chills, myalgias, nausea, vomiting, diarrhea. Symptom onset is 4-60 hours after exposure

Question 20

duration of illness in pontiac fever

Answer 20

1-9 days, it resolves without specific therapy

Question 21

does pontiac fever have signs of lower respiratory tract infection

Answer 21

no

Question 22

when would you suspect pontiac fever

Answer 22

based on epidemiological exposure; bc it is self limiting, testing is not usually performed

Question 23

extrapulmonary legionella infection occurs in

Answer 23

immunocompromised cases

Question 24

T/F cases of extrapulmonary legionella is caused by legionella species other than L. pneumophilia

Answer 24

T

Question 25

dx of extrapulmonary disease in legionella

Answer 25

detection of legionella at the affected site, via culture or PCR

Question 26

tx of legionnares dx

Answer 26

levofloxacin, azithromycin for min of 5 days (both bactericidal), they achieve high intracellular concentrations and penetrate lung tissue, and are active agaisnt all legionella species that cause human infection

Question 27

T/F up to 44% of legionnaires dx pts need ICU admission

Answer 27

T

Question 28

do pts with confirmed or suspected legionella infections need isolation

Answer 28

no

Question 29

primary method for controlling legionella infection in water supply

Answer 29

copper silver ionization, hyperchlorination, thermal shock, chlorine dioxide, monochloramine, point of use filters