Lecture 24 Legionella

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Lecture 24 Legionella

  1. 1. ‫بسم ا الرحمن الرحيم‬ GENUS: LEGIONELLA Prof. Khalifa Sifaw Ghenghesh
  2. 2.  Gram-negative rods  Requires iron and cysteine for growth – Buffered charcoal yeast-extract agar (BCYE)  Optimum growth temp. >> 35-36oC  Grow better >> 2.5-5% CO2  39 species – Legionella pneumophila
  3. 3. Legionella pneumophila  Divided into 3 subspecies – L. pneumophila ssp. pneumophila – L. pneumophila ssp. fraseri – L. pneumophila ssp. pascullei  L. pneumophila divided to >14 serogroups  Most infections caused by: – L. pneumophila, serogroup 1 (SG1)
  4. 4. Legionella pneumophila (TEM)
  5. 5. CLINICAL SYNDROMES 1. Legionnaires’ Disease – Pneumonia – Incubation period >> 2-10 days – High fever, respiratory distress, cough, confusion and local neurological signs. – Mortality 10% in healthy individuals
  6. 6. 2. Pontiac Fever –A brief febrile influenza-like illness –A high attack rate with no mortality –Source of infection usually is not identified
  7. 7. Impression smear from the lung of a patient fatally infected with L. pneumophila serogroup 1, demonstrating many thin, Gram-negative bacilli (arrows).
  8. 8. Lung cross-section of patient with L. pneumophila infection Gram-negative, coccoid rods
  9. 9. LABORATORY DIAGNOSIS  SPECIMENS – Sputum, bronchial aspirate or washings – Pleural fluid, lung biopsy or autopsy material >> Microscopy examination  CULTURE – BCYE with or without antibiotics – Incubate for 48 hours at 36oC aerobically with 2.5% CO2 – Plates kept for least 10-14 days before discarded as negative – Colonies >> “cut-glass” appearance by plate microscopy or fluorescing blue-white under UV light  IDENTIFICATION – Specific antisera in an immunofluorescence test.
  10. 10.  ANTIGEN TESTS –Urine for legionella antigen by ELISA for identifying L. pneumophila SC1  SEROLOGY – Not reliable
  11. 11. Charcoal-yeast extract agar plate culture of Legionella pneumophila.
  12. 12. Charcoal-Yeast extract agar plate culture of Legionella pneumophilia - Circular offwhite colonies (day 6, at 36oC)
  13. 13. L. pneumophila stained using direct FA technique (400x)
  14. 14. TREATMENT  Erythromycin in high dosage (IV)  Rifampicin, Ciprofloxacin
  15. 15. EPIDEMIOLOGY  Disease occurs in outbreak form due to dissemination of the bacteria in aerosols  Infected aerosols generated from warm water sources: – Ponds of cooling towers of refrigeration plants in air-conditioning systems – Domestic hot water systems in hotels and hospitals – Warm water in nebulizers and oxygen line humidifiers – Whirlpool spa baths and showers
  16. 16. CONTROL  Eradication of Legionella organisms in various kinds of water sources that may give rise to aerosol production.  Eradication by –Heat or disinfection with chlorine or other biocides –Hot water should be above 60oC before distribution

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