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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?
- Legionella pneumophila
- Legionella micdadei
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
- Sporadic cases
- Nonsocomial clusters
- Mortality rate 15-30%
Which organisms cause community acquired pneumonia?
- Chlamydophila pneumonia
- Mycoplsma pneumonia
- Legionella pneumophila
What are the specimen collection for Legionella?
- Bronchoalveolar lavage
- Lung tissue
- Transtracheal aspiration
- 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
- Require Cysteine
- 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
- Alternative drugs: macrolides, clarithomycin, azythromcyin
- Fluroroquinolones: ciproflaxin, doxycycline
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