Legionella Pneumophila Flashcards
Why did they call it as such?
Because there was a conventional legion in a hotel in Philadelphia where around 10% of them died of an unknown pneumonia.
Are they gram negative or positive?
They are gram negative
Are they motile? Spore forming?
they are nonmotile and non-spore forming
Are they aerobic, anaerobic or facultative anaerobes?
They are aerobic
How are they transmitted?
By inhalation from AC
By aspiration from heads of shower
From hospitals (nosocomial infections)
Where do bacteria go directly when they are acquired?
They go to alveoli
In which type of environments they like to live?
They live in moist and warm environments
What is the clinical presentation?
Pontiac fever
Legionnaire’s disease (related to pneumonia)
Which factors affect the pathogenesis?
- 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
Which one is the milder outcome?
Pontiac fever
How does it occur?
It occurs in epidemic waves, anytime during the year
What’s the incubation period?
1 to 2 days like a cold or flu
What are the symptoms?
They are flu like symptoms
Is there a person to person spread? Do we need to have background predisposing factors to be infected?
There is no person to person spread except in a few cases
There is no need for a background predisposing factors
Is there bacteremia? Pneumonia?
There is no bacteremia
There is no pneumonia because it is related to the upper respiratory tract
What is the presentation of legionnaires disease?
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
Do we need to have background predisposing factors to be infected?
There has to be an underlying pulmonary disease in order to be infected
To which part of the respiratory tract it is related?
It is related to the lower respiratory tract, upper respiratory tract manifestations are very rare or absent
Where do bacteria go once acquired?
To the lungs in the alveoli
How some of them resist killing by macrophages in alveoli?
By inhibiting the oxidative burst
What is the difference between this pneumonia and those caused by other bacteria?
Chest pain in this case will be more pronounced
What do we find in alveoli and bronchioles?
Large amount of solidified sputum that’s not expectorated
There is a thick mucus plugs with fibrin, RBCs, PMN and macrophages
Is it a systemic type of infection? M
Yes it is, it can spread via blood or lymphatic chain with activity of LPS
Where bacteria could be present after spread?
In intestines, liver, spleen, kidneys, lymph nodes, brain
What does it cause when it is in the intestines?
Watery diarrhea, nausea, vomiting, high fever
Where bacteria can be detected when they spread to kidneys?
In urine
What does it cause when it spreads to the brain?
Nervousness and unconsciousness
What’s the incubation period?
2 to 10 days
Is it self-limited? What is the mortality rate?
It is not self-limited, it requires antibiotic therapy
The mortality rate is 15 to 20%
Which prevention should be taken in consideration? Is there any vaccine?
Cleaning and disinfection of tanks and reservoirs with disinfectants and detergents
There is no vaccine
From where the specimen is taken?
It can be taken from sputum bit it is not always present, so we do a bronchioloalveolar lavage, or a bronchoscopy
What is their medium of growth? What does it contain?
The BCYE (buffer charcoal yeast extract) It contains cysteine without which growth isn’t possible
Which other tests are done?
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
Which antibiotics are given?
Quinolones and azithromycin for at least 2 weeks if it is simple without complications, and for at least 3 weeks if there is complications
What’s the treatment in this case? The mortality rate?
it is self limited so no need for treatment
Mortality rate is less than 1%
