Micro Test 3: Legionella
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Legionnaires' Disease or legionellosis is caused by what bacteria? What does it present as?
- Legionella pneumophilia
- Presents as acute pneumonia/ acute respiratory infection
What kind of agar do your culture Legionella on?
Charcoal yeast extract agar
What bacteria do you culture on Charcoal Yeast Extract Agar? Is this a fastidious organism?
- No, charcoal is present because it removes impurities.
- "Legionnaires must be pure."
Microscopically where is Legionella bacteria found?
Facultative intracellular parasite
Found as an intracellular parasite in free-living protozoa (amoeba's etc.)
Which species and serogroup of Legionella causes most cases in the US?
L. pneumophila, sergroup 1 (Lp-1)
- 1) Gram-N
- 2) Aerobic
- 3) Non-encapsulated
Legionellosis: Endogenous or exogenous infection?
Exogenous (environmentally-friendly...because obviously you can't just say exogenous)
2 Forms of Legionellosis
- 1) Legionnaires' Disease: Pneumonia potentially fatal
- 2) Pontiac Fever: Self-limiting influenza-like
Potentially fatal pneumonia form of Legionella
Self-limiting influenza-like form of Legionella
Which form of Legionellosis occurs as an epidemic?
Pontiac Fever ("That's why I hate pontiacs")
Which form of Legionellosis can occur as an epidemic, sporadically, or as a nosocomial infection?
Can Legionellosis be transmitted person-to-person?
- Thought to be aerosolized infection
When is one most likely to get Legionnaire's Disease? Does it require tx?
When is one most likely to get Pontiac Fever? Does it require tx?
Year round, self-limited
Whichis more fatal, Legionnaires' Disease or Pontiac Fever?
Legionnaire's Disease is more likely fatal (15-20% or higher) than Pontiac fever (<1%)
Legionella: Produces inhibitor of ________
Which bacteria produces an enzyme that inhibits oxidative burst? What does this allow the bacteria to do?
- Allows bacteria to survive encounters with phagocytic cells (ie. macrophages, neutrophils, etc.)
Name 3 enzymes Legionella releases into growth medium.
Hemolysin, protease, aminopeptidase
Legionella is found in ____ and is usually transmitted by _____. Can form biofilms on?
- aerosols (showers and respiratory therapy equipment, basically any water source that aerosolizers the water)
- surface & drinking water
- biofilms= silicone and rubber
Name 3 Predisoposing factors for Legionella and 2 environmental factors.
- Cigarette smoking
- Chronic lung disease
- High humidity
- Increased rainfall
Does Legionella have to be sent to a lab for diagnosis?
Yes (Legionella = Lab)
In the Legionella, Urinary Antigen Test what is detected?
LP-1 (pneumophilia specific)
Culture test allows you to grow all species and serogroups.
Name 3 problems clinically with Legionella pneumophilia.
- 25% mortality rate
- Can't perform susceptibility testing.
How do you treat Legionellosis?
Fluoroquinolones, Macrolides (Legionnaires are For her Majesty!)
Which bacteria is more commonly seen in an ICU type setting?
Increased occurrence with increased stay.
Gram-N rods of Moraxellaceae family
- 1) Gram-N
- 2) Moraxellaceae family
- 3) Non-motile
- 4) Non-fermeter
- 5) Encapsulated
- 6) Oxidase-N
How many species of the Moraxellaceae family are there currently? What is the most frequent clinical isolate?
17, A. baumannii is the most frequent clinical isolate.
What can be grown on MacConkey media but doesn't ferment?
Which organism doesn't ferment lactose and is oxidase negative?
Ubiquitous organism that is found in pasteurized milk and frozen foods (as well as soil, sink traps, etc.)
Which organism is important in soil demineralization? Where does it colonize healthy adults?
- Acinetobacter baumannii
- Colonizes skin of 25% of healthy adults
Which organism causes suppurative infection in virtually every organ system? Usually limited infection unless host is immunocompromised.
I don't know why they even say immunocompromised. Every organism is going to be more likely to infect you if you don't have an immune system.
Clinical manifestations of A. baumannii (5)
- Pneumonia: Often ICU ventilated patient (mortality >70%)
- Bacteremia: Associated with respiratory infections and IV catheters. Can very rarely cause endocarditis.
- Intracranial Infection: meningitis (can be morphologically confused with N. meningitidis on gram stain.)
- Soft Tissue Infection: Cellulitis
What cause of meningitis can look VERY similar to N. meningitidis on a gram stain?
Most common cause of wound infections in Iraqi war veterans.
(A cine sobra Baumanni, Iraq)
Spread of ____ is a concern with A. baumannii
- MDRAB (Multi-Drug Resistant)
- Can rapidly acqure antibiotic resistance in addition to its intrinsic antibiotic resistance.
1) ___ kb resistance island
2) ___ resistance genes in this island
How was the MDRAB resistance island acquired?
Horizontally, not acquired as a single element
Name 3 bacteria that contributed to the resistance island of MRAB. Which bacteria contributed the most?
- Pseudomonas (44%)- contributed the most
- E. coli
What are the known virulence factors of A. baumannii?
- Polysaccharide capsule
- NO KNOWN CYTOTOXINS
_______ are important in protecting lungs from A. baumannii
Neutrophils (problem for neutropenic patients)
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