Card Set Information
What are the general characteristics of Legionella?
Gram (-) bacilli
Acquired through aerosols
Infected patients may present with a wide variety of conditions
: asymptomatic to life-threatning
What are the most common isolates for Legionella?
What is the Epidemiology of Legionella?
WW in aquatic sources
: rivers, lakes, hot springs and mud
Can tolerate 2-3mg/l may resist water treatment
Found in cooling towers, evaporative condensers, fountains, humidifiers
What are unique characteristics of Legionella?
Capacity to adhere to pipes, rubber, plastic, and sediment
Ability to survive within free living protozoa and algae
Ability to multiply at low temps
What are the diseases caused by Legionella?
Legionaries Disease: febrile pneumonia
Pontiac fever: febrile, no pulmonary involvement
What are characteristics of Legionnarie's Disease?
Occur in community
Mortality rate 15-30%
Which organisms cause community acquired pneumonia?
What are the specimen collection for Legionella?
Urine for Ag detection
What are the specimen requirements for Legionella?
Saline and buffer not used. Na is inhibitory.
Refrigerate if not plated within 2 hours
When sending reference lab freeze at -70C
For blood culture the Isolator (lysis centrifugation system) preferred 10mL
What do you see in the direct examination?
Legionella is pleomorphic G(=) baccilus weakly stained
Organisms maybe found intracellularly
Giemsa and Diff-Quik used for staining
L. micdadei weakly acid fast
Direct fluorescent Ab 94-99% specific
Florescin isothicyanate labeled (FITC)
25-80% sensitive compared to culture
To observe organisms at least 10,000 to 100,000 mL must be present
How do you culture and ID Legionella?
Fastidious, aerobic unable to grow in BA
Buffered charcoal yeast extract (BCYE)
Semiselective BCYE contains polymyxin B, anisomycin, cefamandole, or vancomycin
Acid treatment of contaminated specimens enhances growth of Legionella
What are other culture and ID requirements for Legionella?
Aliquot prepared 1:10 0.2N KCL-HCl and allow to stand 5 min
Inoculate the BCYE medium
Incubate 35C for 7 days
Grayish-white or blue-green colonies seen under the dissecting microscope
Colonies show a "ground-glass appearance"
What is the Urine Antigen test?
L. pneumophila serogroup 1 soluble antigen from urine
Estimated that 85% of Legionella cases caused by this sertype
Can be detected as early as 3 days of infection. Cam persist up to 1 year
Prolonged antigenuria associated with immunosuppression, alcoholism and renal failure
What kind of antimicrobial therapy used?
Treated sucessfully with erythromycin and rifampin
: macrolides, clarithomycin, azythromcyin
: ciproflaxin, doxycycline