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MHD 1 > L27 Pseudomonas and Other Gram Negative Rods > Flashcards

L27 Pseudomonas and Other Gram Negative Rods Flashcards

1
Q

What are the key characteristics of glucose non-fermenting gram-negative bacilli?

A
  1. Gram-negative
  2. Non-spore-forming
  3. Rods or coccobacilli
  4. Obligate aerobes
  5. Good growth seen in 24 hours
  6. Glucose not fermented
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2
Q

What is the natural habitat of glucose non-fermenting gram-negative bacilli?

A

Water, soil, plants, moist areas, hospital environment

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3
Q

Pseudomonas aeruginosa is an aerobic Gram ___ ___ (shape).

A

Negative; rod

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4
Q

What are the major virulence factors of P. aeruginosa?

A
  1. Motility with polar flagella
  2. Mucoid polysaccharide slime layer
  3. Pili on the cell surface
  4. LPS
  5. Pyocyanin
  6. Exotoxin A
  7. Exoenzyme S
  8. Elastase
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5
Q

What factors pre-dispose patients to serious infection with P. aeruginosa?

A
  1. Burn patients
  2. CF patients
  3. Patients with hematologic malignancies
  4. Immunocompromised patients
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6
Q

True or false - P. aeruginosa can be part of the microbial flora in hospitalized patients and ambulatory, immunocompromised hosts.

A

True

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7
Q

What skin infections are caused by pseudomonas?

A
  1. Burn wounds
  2. Folliculitis
  3. Nail infections
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8
Q

What pulmonary infections are caused by/associated with pseudomonas?

A
  1. Asymptomatic colonization
  2. CF and chronic lung disease
  3. Severe necrotizing bronchopneumonia
  4. Ventilator associated pneumonia (VAP)
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9
Q

What is the most common cause of VAP?

A

Pseudomonas

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10
Q

What other infections are caused by Pseudomonas?

A

UTI, ear infections (swimmer’s ear, malignant external otitis, chronic otitis media), eye infections, bacteremia with ecthyma gangrenosum, endocarditis, osteomyelitis

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11
Q

What is ecthyma gangrenosum?

A

A well-recognized but uncommon cutaneous infection most often associated with a P. aeruginosa bacteremia; usually occurs in patients who are critically ill and immunocompromised. It is almost always a sign of pseudomonal sepsis. q

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12
Q

What are the symptoms of bacteremia with ecthyma gangrenosum?

A

Characteristic hemorrhagic pustules or infarcted-appearing areas with surrounding erythema that evolve quickly into necrotic ulcers surrounded by erythema

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13
Q

What are the structural virulence factors of P. aeruginosa?

A
  1. Capsule
  2. Pili
  3. LPS
  4. Pyocyanin
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14
Q

How does exotoxin A function?

A

Exotoxin A blocks protein synthesis and contributes to dermatonecrosis in wounds and tissue damage in lungs

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15
Q

How does exoenzyme S function?

A

Exoenzyme S is an ADP-ribosylating toxin that causes epithelial damage, which facilitates bacterial spread, tissue invasion, and necrosis

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16
Q

How does elastase (Las A and Las B) function?

A

Causes tissue destruction and hemorrhagic lesions by degrading elastin and complement components, and inhibiting neutrophil chemotaxis and function

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17
Q

Describe growth of P. aeruginosa.

A

Grows on blood and MacConkey agar, producing spreading colonies with a metallic sheen. It is temperature tolerant and grows at 42 degrees Celcius.

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18
Q

What are some ID aspects of P. aeruginosa?

A
  1. Glucose non-fermenter
  2. Oxidase positive
  3. Grape-like odor
  4. Produces pyocyanin
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19
Q

How are Pseudomonas infections treated?

A

They are resistant to many common antibiotics used for Gram negative infections due to changes in porins. Combination therapy of cell wall active agent + aminoglycosides are needed for serious systemic infection.

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20
Q

What is the habitat of Burkholderia pseudomallei?

A

Soil, water, and vegetation of Southeast Asia

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21
Q

What disease does Burkholderia pseudomallei cause?

A

Melioidosis

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22
Q

B. pseudomallei is a category B ___.

A

Biothreat agent

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23
Q

What are the three types of melioidosis?

A
  1. Acute disease: septicemia with metastatic lesions
  2. Subacute disease: most common; TB-like disease with cellultis and lymphangitis
  3. Chronic disease: localized chronic cellultis
24
Q

How is chronic melioidosis treated?

A

Treat with antibiotics before draining to avoid bacteremia

25
What is the habitat of B. cepacia?
Water sources, wet surfaces, detergent solutions
26
What diseases are caused by B. cepacia?
1. Respiratory tract infections (60% isolated from these) 2. Problematic in patients with CF and CGD 3. UTIs 4. Septicemia
27
What is the most common autosomal recessive genetic disease in Caucasians?
CF
28
What causes CF?
A mutation in the CFTR gene (CF transmembrane conductance regulator); this gene regulates components of sweat, digestive juices, and mucus
29
How is CF inherited?
Autosomal recessive
30
Mutation in CFTR results in defects in innate immunity, including...
...decreased NO levels, failure to internalize bacteria in bronchial epithelial cells, increased inflammation of CF airway, and abnormal electrolyte transport, which causes thick, dry, sticky mucus.
31
Abnormal mucus adversely effects mucocilliary clearance and provides and ideal ___ for chronic lung infection.
Niche
32
Over 85% of premature deaths in CF are due to...
...cardiopulmonary failure secondary to chronic lung infection
33
What is the median life expectancy in US patients with CF?
37 years
34
What are pulmonary exacerbations?
Cellular defects resulting in thickened viscous mucus layer in the respiratory tract and impaired innate immunity.
35
When does pulmonary exacerbation occur?
When there is impaired mucociliary transport and chronic infection with a number of bacterial species
36
What characterizes pulmonary exacerbation?
Recruitment of neutrophils, cytokine release, and high level of neutrophil derived elastases causing significant lung pathology
37
Which pathogens are known to cause infection in CF/chronic lung disease?
1. S. aureus 2. P. aeruginosa 3. B. cepacia complex
38
What infections are caused by Stenotophomonas maltophilia?
Bacteremia, pneumonia, meningitis, wound infections, UTIs
39
What is the habitat of Stenotrophomonas maltophilia?
Worldwide distribution, soil, water, animals, vegetation, crops; not park of normal flora but can be recovered from almost any clinical site
40
From which clinical site is Stenotrophomonas maltophilia recovered most frequently?
Respiratory tract (60%)
41
>95% of all clinical infections caused by S. maltophilia are ___.
Hospital-acquired
42
S. maltophilia is the second leading cause of ___.
Gram-negative non-fermentive bacillary infections.
43
What is the hallmark of S. maltophilia disease?
Life-threatening systemic infections in debilitated patients (usually with cancer)
44
Describe the lab features of S. maltophilia.
Good growth on BAP and MacConkey, oxidase negative, some strains have yellow pigment
45
How is S. maltophilia treated?
This bacteria is very INHERENTLY resistant to beta-lactams, including imipenem and aminoglycosides. The drug of choice is trimethoprim-sulfamethoxazole (SXT).
46
What is the habitat of E. meningoseptica?
Soil, water, plants, food-stuffs, may exist in water systems and wet surfaces
47
Nosocomial outbreaks of E. meningoseptica are often traced to ___.
Breast pumps used in hospital nurseries
48
E. meningoseptica is associated with neonatal ___.
Meningitis
49
What are the lab features of E. meningoseptica?
1. Oxidase positive 2. Pale yellow pigment on BAP 3. Poor growth on MacConkey
50
How is E. meningoseptica treated?
Very INHERENTLY resistant to beta lactam agents and aminoglycosides; current methods are unreliable
51
What is the habitat of A. baumannii?
Free living in water and soil, isolated foods, hospital air, inanimate objects, human sources
52
What is the most common gram-negative organism carried on the skin of hospital personnel?
A. baumannii
53
What diseases does A. baumannii cause?
Implicated in community acquired and nosocomial infections
54
___ colonizes 45% of inpatient tracheostomy patients.
A. baumanii
55
What are the lab features of A. baumannii?
1. Coccobacilli 2. Good growth on BAP and MacConkey 3. Oxidase negative 4. Non-motile
56
How are A. baumannii treated?
Imipenem or merepenem, fluroquinolone + amikacin or ceftazidime, ampicillin-sulbactam, colistin

MHD 1 (58 decks)

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