بسم الله الرحمن الرحيمبسم الله الرحمن الرحيم

GENUS:LEGIONELLA

Prof. Khalifa Sifaw Ghenghesh

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

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)

Legionella pneumophila (TEM)

Legionella pneumophila (TEM)

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

2. Pontiac Fever– A brief febrile influenza-like

illness– A high attack rate with no

mortality– Source of infection usually is

not identified

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).

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

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.

ANTIGEN TESTS– Urine for legionella antigen

by ELISA for identifying L. pneumophila SC1

SEROLOGY– Not reliable

Charcoal-yeast extract agar plate culture of Legionella pneumophila.Charcoal-yeast extract agar plate culture of Legionella pneumophila.

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)

L. pneumophila stained using direct FA technique (400x)

L. pneumophila stained using direct FA technique (400x)

TREATMENTTREATMENT

Erythromycin in high dosage (IV)

Rifampicin, Ciprofloxacin

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

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