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1. Historical background
Characteristics of legionella
Virulence factors
Pathogenesis
Clinical manifestations
Diagnostic laboratory tests
Immunity against legionella
Normal habitat & Epidemiology
Transmission and control
Treatment
Summary
references

2. Historical background
Characteristics of legionella
Virulence factors
Pathogenesis
Clinical manifestations
Diagnostic laboratory tests
Immunity against legionella
Normal habitat & Epidemiology
Transmission and control
Treatment
Summary
references

3. Historical Background
and Epidemiology
Historical Background
The name legionella originates
from a widely publicized outbreak
of pneumonia in persons attending
an American Legion convention in
Philadelphia in 1976.
In a hotel on the occasion of a United
States army veterans’ meeting
(Fraser et al., 1977).

4. Legionellaceae are facultative intracellular parasites
that cause primarily respiratory tract infections.
Legionella are :
• gram-negative
• slender rods
• unencapsulated
• fastidious,
• Aerobic
• catalase-positive
• Most produce gelatinase and ß-lactamase
• 0.5–1 m wide and 2–50 m long.
• poorly stained by Gram's stain
This has been attributed to the presence of the branched chain
fatty acids that are a major component of the cell walls.
Bacterial Characteristics

5. • Motile by means of one or more polar or subpolar flagella
• grown on complex media such as buffered charcoal-yeast
extract (BCYE) agar with ;
ketoglutarate,
pH of 6.9,
temperature 35 °C, and
90% humidity.
• Legionellae grow slowly;
3 days of incubation with BCYE & ≥2 weeks in blood cultures
• Colonies are round or flat, colorless to iridescent pink or blue

6. Virulence factors
The Legionellae make:
• proteases,
• phosphatase,
• lipase,
• DNase, and
• Rnase
• A major secretory protein, a
metalloprotease, has hemolytic
and cytotoxic activity; however,
this protein has not been shown
to be a required virulence factor.

7. Pathogenesis
Legionellae are intracellular pathogens of macrophages, by
which they are phagocytosed in a process involving ;
1. Both virulent and non-virulent strains are phagocytosed
2. Virulent strains can multiply inside the phagocytes and
are able to inhibit the fusion of phagosomes with
lysosomes
 non-virulent strains do not multiply
3. The bacteria multiply within the vacuoles until they are
numerous,
4. The cells are destroyed, the bacteria are released, and
infection of other macrophages then occurs.
(transferrin-iron) is essential for the process of intracellular
growth of the bacteria, but other factors important to
the processes of growth, cell destruction, and tissue
damage are not well understood.

9. Clinical Findings
Legionellaceae primarily cause respiratory tract infections.
There are two distinctly different presentations:
1. Legionnaires' disease and
2. Pontiac fever
Asymptomatic infection is common in all age groups. in which,The
incidence of clinically significant disease is highest in men over
age 55 years.
Factors associated with high risk include:
• smoking,
• chronic bronchitis and emphysema,
• steroid and other immunosuppressive treatment (as in renal
transplantation)
• cancer chemotherapy, and
• diabetes mellitus.
 When pneumonia occurs in patients with these risk factors,
legionella should be investigated as the cause.

10. • L.neumophilia causes
Legionnaires' disease can have
symptoms like many other forms
of pneumonia, so it can be hard
to diagnose at first.
Signs of Legionnaires' disease can
include:
Cough
Shortness of breath
High fever
Muscle aches
Headaches
These symptoms usually begin 2 to
14 days after being exposed to
the bacteria.
Clinical manifestations

11. • Chest x-rays
reveal patchy,
often multilobar
consolidation.
• There may be
leukocytosis,
hyponatremia,
hematuria (and
even renal
failure), or
abnormal liver
function.

12. Potanic fever
• L .pneumophila also produces a disease called "Pontiac fever," after the
clinical syndrome that occurred in an outbreak in Michigan.
characteristics
 fever and chills,
 myalgia,
 malaise, and
 headache ,that develop over 6–12 hours. Dizziness, photophobia, neck
stiffness, and confusion also occur.
• The symptoms of Pontiac fever are similar to those of Legionnaires’ disease
and usually last for 2 to 5 days. Pontiac fever is different from
Legionnaires' disease because the patient does not have pneumonia.
• Symptoms go away on their own without treatment.

13. Specimens
The organisms can be recovered from:
• bronchial washings
• pleural fluid
• lung biopsy specimens or
• blood
 Isolation of legionella from sputum is more difficult
because of the predominance of bacteria of the
normal flora. Legionella is rarely recovered from
other anatomic sites.
Smears
 Legionellae are not demonstrable in Gram-stain
 Direct fluorescent antibody tests, but the test has
low sensitivity compared with culture
 Silver stains are sometimes used on tissue
specimens.
Culture
Specimens are cultured on BCYE agar & can be rapidly
identified by immunofluorescence staining.
BCYE agar containing antibiotics can be used

14. Specific Tests
The urine antigen test is specific for L. pneumophila serotype 1.
Serologic Tests
Levels of antibodies to legionellae rise slowly during the illness.
Serologic tests have :
a sensitivity of 60–80% and
a specificity of 95–99%.
Serologic tests are most useful in obtaining a retrospective diagnosis
in outbreaks of legionella infections.

15. • Infected patients make antibodies against legionella but the peak
antibody response may not occur until 4–8 weeks after
infection.
• The roles of antibodies and cell-mediated responses in
protective immunity in humans have not been defined.
• The host defense against Legionella relies principally on cell-
mediated immune mechanisms.
• One protein produced by L. pneumophila, the major secretory protein (MSP,
39kDa), is able to
• induce protective cell-mediated immunity without being a virulence factor
(Blander & Horowitz,1991).
No vaccine has so far been tested in humans!!!

16.  Legionellae are ubiquitous in warm moist
environments
 Legionellae grow best in warm water in the
presence of amebas and water bacteria.
 The Legionellaceae family includes 34 species
& many of them lives in;
soil and water,
cooling towers
evaporative condensers
water distribution systems
 85 to 90 % of human disease is caused by a
single species, Legionella pneumophila.
Normal habitat &
epidemiology
Hot tubs
Cooling towers
Hot water tanks
Large plumbing systems
Decorative fountains

17. Epidemiology
L .pneumophila is responsible for approximately
1% to 3% of community-acquired pneumonias,
13% of those acquired in the hospital
• It is estimated that about 25,000 to 100,000
Legionella infections occur annually
• The resulting mortality rate, which ranges up to 40% in
untreated immunocompetent patients
• L. pneumophila is estimated to be responsible for 80%
to 85% of reported cases of Legionella infections

18. Transmission and Control
 Transmission

19.  Control
• Hyperchlorination
and superheating of
water can help
control the
multiplication of
Legionellae in
water and in air-
conditioning
systems.

20. • Legionellae are susceptible to
erythromycin and some other drugs.
The treatment of choice is erythromycin,
which has been effective even in
immunocompromised patients.
• Rifampin, 10–20 mg/kg/d, has been
used in patients whose response to
treatment was delayed.
• Assisted ventilation may be necessary,
and management of shock is essential.

21.  Legionnaires'
disease is the
more severe
form and can be
fatal.
 Pontiac fever is
the far milder
form of the
illness.
Symptoms of
Legionnaires'
disease include
fever, chills, and
a cough. At its
worst,
Legionnaires'

22. ’’ Jawetz, Melnick, & Adelberg's Medical
Microbiology, 24th Edition by Vishal :
Lippincott’s microbiology
Addis DG et al. (1989). Community acquired
Legionnaires’ disease associated with a cooling
tower: evidence for longer distance transport of
Legionella pneumophila. American Journal of
Epidemiology, 130:557–568.
Adeleke A et al. (1996).

23. End of discussion!!!
relax..!!!!