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microbiology 1 > FASTIDIOUS GRAM NEGATIVE RODS. PART 5 > Flashcards

FASTIDIOUS GRAM NEGATIVE RODS. PART 5 Flashcards

Legionella pneumophila

1
Q

What is the most frequent cause of human legionellosis?

A

Legionella pneumophila

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2
Q

What type of pneumonia does L. pneumophila commonly cause?

A

community-acquired and nosocomial pneumonia

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3
Q

What are the two distinct clinical syndromes associated with legionellosis

A

Legionnaires’ disease: This is a severe form of pneumonia caused by L. pneumophila.

Pontiac Fever: A milder, flu-like illness caused by the same bacterium.

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4
Q

Where is L. pneumophila associated with environmental water sources?

A

L. pneumophila is chiefly associated with environmental water sources such as air conditioners and water-cooling towers.

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5
Q

What has been attributed to outbreaks of pneumonia in hospitals?

A

Outbreaks of pneumonia in hospitals have been attributed to the presence of L. pneumophila in water taps, sinks, and showers.

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6
Q

What is the exact incidence of legionellosis worldwide?

A

The exact incidence of legionellosis worldwide is unknown.

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7
Q

Which bacterium causes approximately 90% of pneumonia attributed to legionellae?

A

L. pneumophila causes approximately 90% of pneumonia attributed to legionellae.

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8
Q

What is the predominant mode of transmission for L. pneumophila?

A

The predominant mode of transmission for L. pneumophila is aspiration.

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9
Q

What are the other modes of transmission for L. pneumophila?

A
  1. Oropharyngeal colonization: This can lead to infection, especially if the person drinks contaminated water.
  2. Aerosol exposure: Contaminated air conditioners, nebulizers, and humidifiers can release aerosols containing the bacterium.
  3. Direct instillation into the lung: This can occur during respiratory tract manipulations.
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10
Q

Who is considered the typical candidate for Legionnaires’ disease?

A

The typical candidate for Legionnaires’ disease is an older man who smokes and consumes substantial amounts of alcohol.

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11
Q

Which patient groups are predisposed to Legionella pneumonia?

A

Patients with acquired immunodeficiency syndrome (AIDS), cancer, or transplants (especially renal transplants), as well as patients being treated with corticosteroids, are predisposed to Legionella pneumonia.

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12
Q

5 clinical manifestations of legionella pneumophila

A
  1. fever
  2. chills
  3. headache
  4. diarrhea
  5. vomiting
  6. fluid in the lungs
  7. pain in the chest and abdomen
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13
Q

How are Legionella organisms taken up after inhalation?

A

After inhalation, Legionella organisms are taken up into amoeboid phagocytes by a spirally progressing form of phagocytosis.

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14
Q

Where do Legionella organisms thrive inside the host cell?

A

They thrive inside the acidic conditions of the phagolysosome, where they multiply and eventually rupture the cell.

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15
Q

What type of cells do Legionella organisms adapt well to living inside

A

Legionella organisms adapt well to living inside amoeboid white blood cells.

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16
Q

What is the major virulence factor of Legionella pneumophila?

A

The major virulence factor of the organism is lipopolysaccharide (endotoxin).

17
Q

Types of specimens needed for legionella pneumophila testing

A
  1. Bronchial washings
  2. Lung biopsy
  3. Pleural fluid
18
Q

Rapid test methods for identification of legionella pneumophila

A
  1. urine antigen test
  2. Direct fluorescent antibody test (DFA)
  3. DNA detection serological tests
19
Q

Treatment of legionella pneumophila

A
  1. Azithromycin or Erythromycin alone or with Rifampin
20
Q

Biochemical tests results for legionella pneumophila

A
  1. Oxidase positive
  2. Catalase Positive
  3. Motile by polar flagella
21
Q

What type of plate is used for inoculating the sputum specimen for legionella pneumophila testing

A

A nonselective buffered charcoal yeast extract (BCYE) plate is used

22
Q

How do colonies appear on the nonselective BCYE plate?

A

colonies appear blue-green or gray-white and glistening.

23
Q

What is the purpose of the selective BCYE plate?

A

The selective BCYE plate contains added antibiotics and is inoculated with the same specimen but treated before inoculation. It is used to identify the smallest visible colonies.

24
Q

How do colonies appear on the selective BCYE plate after 2-4 days?

A

On the selective BCYE plate, colonies are grayish-white and glistening after 2-4 days

25
Q

Prevention of legionella pneumophila

A
  1. Reducing cigarette and alcohol consumption
  2. Eliminating aerosols from water sources, and
    3Reducing the incidence of Legionella in hospital water supplies by using high
    temperatures and hyper chlorination.
    ~ There is no vaccine.

microbiology 1 (27 decks)

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