IDC Mycoplasma/Legionella

  1. What are the general characteristics of Legionella?
    • Ubiquitous
    • Gram (-) bacilli
    • Acquired through aerosols
    • Infected patients may present with a wide variety of conditions: asymptomatic to life-threatning
  2. What are the most common isolates for Legionella?
    • Legionella pneumophila
    • Legionella micdadei
  3. 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
  4. 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
  5. What are the diseases caused by Legionella?
    Legionaries Disease: febrile pneumonia

    Pontiac fever: febrile, no pulmonary involvement
  6. What are characteristics of Legionnarie's Disease?
    • Occur in community
    • Sporadic cases
    • Nonsocomial clusters
    • Mortality rate 15-30%
  7. Which organisms cause community acquired pneumonia?
    • Chlamydophila pneumonia
    • Mycoplsma pneumonia
    • Legionella pneumophila
  8. What are the specimen collection for Legionella?
    • Sputum
    • Bronchoalveolar lavage
    • Blood
    • Lung tissue
    • Transtracheal aspiration
    • Urine for Ag detection
  9. 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
  10. 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
  11. 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
  12. 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"
  13. 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
  14. What kind of antimicrobial therapy used?
    • Treated sucessfully with erythromycin and rifampin
    • Alternative drugs: macrolides, clarithomycin, azythromcyin
    • Fluroroquinolones: ciproflaxin, doxycycline
Card Set
IDC Mycoplasma/Legionella