Lecture 24 Legionella
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Transcript of Lecture 24 Legionella
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بسم الله الرحمن الرحيمبسم الله الرحمن الرحيم
GENUS:LEGIONELLA
Prof. Khalifa Sifaw Ghenghesh
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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
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Legionella pneumophilaLegionella 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)
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Legionella pneumophila (TEM)
Legionella pneumophila (TEM)
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CLINICAL SYNDROMESCLINICAL SYNDROMES
1. Legionnaires’ Disease– Pneumonia– Incubation period >> 2-10 days– High fever, respiratory distress,
cough, confusion and local neurological signs.
– Mortality10% in healthy individuals
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2. Pontiac Fever– A brief febrile influenza-like
illness– A high attack rate with no
mortality– Source of infection usually is
not identified
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Impression smear from the lung of a patient fatally infected with L. pneumophila
serogroup 1, demonstrating many thin, Gram-negative bacilli (arrows).
Impression smear from the lung of a patient fatally infected with L. pneumophila
serogroup 1, demonstrating many thin, Gram-negative bacilli (arrows).
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Lung cross-section of patient with L. pneumophila infection
Gram-negative, coccoid rods
Lung cross-section of patient with L. pneumophila infection
Gram-negative, coccoid rods
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LABORATORY DIAGNOSISLABORATORY 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.
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ANTIGEN TESTS– Urine for legionella antigen
by ELISA for identifying L. pneumophila SC1
SEROLOGY– Not reliable
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Charcoal-yeast extract agar plate culture of Legionella pneumophila.Charcoal-yeast extract agar plate culture of Legionella pneumophila.
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Charcoal-Yeast extract agar plate culture of Legionella pneumophilia - Circular off-
white colonies (day 6, at 36oC)
Charcoal-Yeast extract agar plate culture of Legionella pneumophilia - Circular off-
white colonies (day 6, at 36oC)
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L. pneumophila stained using direct FA technique (400x)
L. pneumophila stained using direct FA technique (400x)
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TREATMENTTREATMENT
Erythromycin in high dosage (IV)
Rifampicin, Ciprofloxacin
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EPIDEMIOLOGYEPIDEMIOLOGY 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
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CONTROLCONTROL
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