Legionella Flashcards

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1
Q

Morphology (2)

A

Gram Negative coccobacilli

Motile

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2
Q

Diseases (3)

A

Atypical pneumonia

Community-acquired pneumonia

Nosocomial pneumonia

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3
Q

Species (2)

A

L.pneumophila (most common)

L.longbeachae

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4
Q

Gram stain Appearance

A

POORLY staining, THIN gram-negative coccobacilli

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5
Q

Culture (5)

A

Buffered Charcoal Yeast Extract (BCYE) agar

Incubation 3-5% CO2 for 3-4 days at 37 degrees

BLUE-GREEN, glistening, convex, circular colonies with CUT-GLASS type internal granular speckling by plate microscopy

Blue-white AUTOFLUORESCENCE on long wave UV light (Fluorescent Labeled Monoclonal Antibody)

STICKY appearance of colony

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6
Q

Habitat (4)

A

Aquatic bacterium in biofilm, single or living inside water amoeba

Multiplies inside amoeba and kills host

Also present in air-conditioning ducts and cooling towers as biofilms

HEAT-RESISTANT and CHLORINE-RESISTANT

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7
Q

Transmission (2)

A

To humans by RESPIRATORY route by aerosol (liquid-droplet) inhalation

NO HUMAN-HUMAN transmission

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8
Q

Intracellular Pathogen (2)

A

In water amoeba

In macrophage in human lung

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9
Q

How is Legionella internalized?

A

By coiling phagocytosis of Ameoba and Macrophage

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10
Q

Pathogenesis (5)

A

1- Entry into respiratory tract by aspiration of water containing organism or by inhalation of contaminated aerosol

2- Organism phagocytosed by alveolar macrophage

3- Phagosome fails to fuse with lysosome (NO ACIDIFICATION)

4- Multiplication of organism in protected environment of phagosome

5- Rupture of cell with release of new crop of bacteria

(RER allows pathogen to obtain nutrients from host)

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11
Q

Virulence Factors (5)

A

Mip—> (Macrophage infectivity promoter) —> Required for infection of Phagocytic cells, Protozoa

Dot/Icm —> (Defective for organelle trafficking) / (Intracellular multiplication) —> Diverts phagosome from Endocytic pathway; Type IV secretory system (syringe-like) for secretion of virulence factors required in Phagocytic cells and Protozoa

Pmi —> Protozoan and macrophage infectivity

Mak —> Macrophage killing

Mil—> Macrophage-specific infectivity locus

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12
Q

Entry in Ameoba / Macrophage

A

Ameoba —> Receptor-mediated uptake, Requires dot/icm, Gal/GalNac receptor

Macrophage —> Actin dependent, Requires dot/icm

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13
Q

Release from Ameoba / Macrophages

A

Ameoba —>Necrosis (pore formation)

Macrophages —> Necrosis (pore formation), Apoptosis

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14
Q

Radiology

A

Patchy UNILOBAR infiltrates

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15
Q

Systemic Involvement (3)

A

Diarrhea

Kidney dysfunction

Liver dysfunction

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16
Q

Other infections (5)

A

Wound abscess

Encephalitis

Endocarditis

Cellulitis

Peritonitis

17
Q

Pontiac Fever (2)

A

Flu-like illness

Lungs NOT affected

18
Q

Diagnosis (3)

A

MOST COMMON —> URINE (antigen detection by ELISA especially serogroup 1)

Respiratory secretions (BAL) —> Fluorescent antibody tests

NOT GRAM STAIN!!!!

19
Q

Serodiagnosis (serum antibodies)

A

Acute and Convalescent (recovered) sera taken 2 weeks apart:

  • Demonstration of FOUR-FOLD RISE in Legionella antibody-titre by INDIRECT FLUORESCENT ANTIBODY TEST
  • Single serum sample with titre of 256 or more with clinical characteristic is diagnostic
20
Q

Antimicrobial Therapy (3)

A

1- Macrolides (Erythromycin, Azithromycin)

2- Flouroquinlone (Ciprofloxacin, Levofloxacin)

3- Tetracycline

21
Q

Control (3)

A

Monochloramine (CHLORINE = NOT EFFECTIVE)

UV Light treatment

Superheating water to 60 degrees