Legionella Pneumophila

Question 1

Why did they call it as such?

Answer 1

Because there was a conventional legion in a hotel in Philadelphia where around 10% of them died of an unknown pneumonia.

Question 2

Are they gram negative or positive?

Answer 2

They are gram negative

Question 3

Are they motile? Spore forming?

Answer 3

they are nonmotile and non-spore forming

Question 4

Are they aerobic, anaerobic or facultative anaerobes?

Answer 4

They are aerobic

Question 5

How are they transmitted?

Answer 5

By inhalation from AC
By aspiration from heads of shower
From hospitals (nosocomial infections)

Question 6

Where do bacteria go directly when they are acquired?

Answer 6

They go to alveoli

Question 7

In which type of environments they like to live?

Answer 7

They live in moist and warm environments

Question 8

What is the clinical presentation?

Answer 8

Pontiac fever

Legionnaire’s disease (related to pneumonia)

Question 9

Which factors affect the pathogenesis?

Answer 9

• Age, as age increases cellular immunity decreases (Legionnaire‘s disease is never seen in youngsters)
• Immune status, mainly people with background cardiopulmonary diseases, or smokers
• Inoculum size
• Degree of exposure to the source i.e. how long we have been exposed to the shower heads

Question 10

Which one is the milder outcome?

Answer 10

Pontiac fever

Question 11

How does it occur?

Answer 11

It occurs in epidemic waves, anytime during the year

Question 12

What’s the incubation period?

Answer 12

1 to 2 days like a cold or flu

Question 14

What are the symptoms?

Answer 14

They are flu like symptoms

Question 15

Is there a person to person spread? Do we need to have background predisposing factors to be infected?

Answer 15

There is no person to person spread except in a few cases

There is no need for a background predisposing factors

Question 16

Is there bacteremia? Pneumonia?

Answer 16

There is no bacteremia

There is no pneumonia because it is related to the upper respiratory tract

Question 17

What is the presentation of legionnaires disease?

Answer 17

It comes as: epidemics in late summer or fall, or sporadic i.e. nosocomial infections in people having a special surgical procedure, or endemic throughout the year

Question 18

Do we need to have background predisposing factors to be infected?

Answer 18

There has to be an underlying pulmonary disease in order to be infected

Question 19

To which part of the respiratory tract it is related?

Answer 19

It is related to the lower respiratory tract, upper respiratory tract manifestations are very rare or absent

Question 20

Where do bacteria go once acquired?

Answer 20

To the lungs in the alveoli

Question 21

How some of them resist killing by macrophages in alveoli?

Answer 21

By inhibiting the oxidative burst

Question 22

What is the difference between this pneumonia and those caused by other bacteria?

Answer 22

Chest pain in this case will be more pronounced

Question 23

What do we find in alveoli and bronchioles?

Answer 23

Large amount of solidified sputum that’s not expectorated

There is a thick mucus plugs with fibrin, RBCs, PMN and macrophages

Question 24

Is it a systemic type of infection? M

Answer 24

Yes it is, it can spread via blood or lymphatic chain with activity of LPS

Question 25

Where bacteria could be present after spread?

Answer 25

In intestines, liver, spleen, kidneys, lymph nodes, brain

Question 26

What does it cause when it is in the intestines?

Answer 26

Watery diarrhea, nausea, vomiting, high fever

Question 27

Where bacteria can be detected when they spread to kidneys?

Answer 27

In urine

Question 28

What does it cause when it spreads to the brain?

Answer 28

Nervousness and unconsciousness

Question 29

What’s the incubation period?

Answer 29

2 to 10 days

Question 30

Is it self-limited? What is the mortality rate?

Answer 30

It is not self-limited, it requires antibiotic therapy

The mortality rate is 15 to 20%

Question 31

Which prevention should be taken in consideration? Is there any vaccine?

Answer 31

Cleaning and disinfection of tanks and reservoirs with disinfectants and detergents
There is no vaccine

Question 32

From where the specimen is taken?

Answer 32

It can be taken from sputum bit it is not always present, so we do a bronchioloalveolar lavage, or a bronchoscopy

Question 33

What is their medium of growth? What does it contain?

Answer 33

The BCYE (buffer charcoal yeast extract)
It contains cysteine without which growth isn’t possible

Question 34

Which other tests are done?

Answer 34

Direct fluorescent Ab test
Antigen detection
PCR
Serology
Liver tests, to see if there is abnormalities in certain liver functions
Blood tests, they indicate anemia, thrombocytopenia, leukopenia since the bacteria have spread

Question 35

Which antibiotics are given?

Answer 35

Quinolones and azithromycin for at least 2 weeks if it is simple without complications, and for at least 3 weeks if there is complications

Question 36

What’s the treatment in this case? The mortality rate?

Answer 36

it is self limited so no need for treatment

Mortality rate is less than 1%