1. ‫بسم ا الرحمن الرحيم‬
GENUS:
LEGIONELLA
Prof. Khalifa Sifaw Ghenghesh

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. 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. Legionella pneumophila
(TEM)

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. 2. Pontiac Fever
–A brief febrile influenza-like
illness
–A high attack rate with no
mortality
–Source of infection usually is
not identified

7. Impression smear from the lung of a patient
fatally infected with L. pneumophila
serogroup 1, demonstrating many thin,
Gram-negative bacilli (arrows).

8. Lung cross-section of patient with
L. pneumophila infection
Gram-negative, coccoid rods

10. 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.

11.  ANTIGEN TESTS
–Urine for legionella antigen
by ELISA for identifying L.
pneumophila SC1
 SEROLOGY
– Not reliable

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

13. Charcoal-Yeast extract agar plate culture
of Legionella pneumophilia - Circular offwhite colonies (day 6, at 36oC)

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

15. TREATMENT
 Erythromycin in high dosage
(IV)
 Rifampicin, Ciprofloxacin

16. 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

17. 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