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MHD #3 > Pseudomonas aeruginosa 
and Other Non-Fermenting Bacilli > Flashcards

Pseudomonas aeruginosa 
and Other Non-Fermenting Bacilli Flashcards

1
Q

*Describe the type of patients who acquire Pseudomonas aeruginosa infections

A

Burn patients
Cystic fibrosis patients
Patients with hematologic malignancies
Immunocompromised patients
Can be part of the microbial flora in hospitalized patients and ambulatory, immunocompromised hosts
Common cause of ventilator associated pneumonia (people on ventilators)

-its an opportunistic pathogen/ wont affect healthy people

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2
Q

*List major toxins produced by Pseudomonas aeruginosa and describe their principle effect on human cells.

A

Exotoxin A

Exoenzyme S

Elastase

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3
Q

*Discuss the association of Burkholderia cepacia and pulmonary infection in cystic fibrosis patients

A

Cellular defect results in thickened viscous mucus layer in resp tract and impaired innate immunity
Results in impaired mucocillary transport and chronic infection with limited number of bacterial species
Chronic infection leads to intermittent pulmonary exacerbations

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4
Q

*Describe the gene defect and resultant pathology of cystic fibrosis disease

A

Caused by a mutation in gene: cystic fibrosis transmembrane conductance regulator(CFTR)

  • Mutation in CFTR results in defects in innate immunity including decreased nitric oxide levels, failure to internalize bacteria in bronchial epithelial cells, increased inflammation in CF airway and abnormal electrolyte transport causing thick, dry, sticky mucus
  • Abnormal mucus adversely effects mucocilliary clearance providing ideal niche for chronic lung infection
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5
Q

*diseases associated with Stenotrophomonas maltophilia

A

Opportunistic infection

  • Bacteremia
  • Pneumonia
  • Meningitis
  • Wound infections
  • Urinary tract
  • Treatment complicated by resistance to many commonly used antibiotics

> 95% of all clinical infections are hospital acquired
2nd leading cause of gram-negative nonfermentative bacillary infections

Hallmark of S. maltophilia disease is life-threatening systemic infections in debilitated patients (usually malignancy)

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6
Q

*diseases associated with Burkholderia cepacia

A

respiratory tract infections. Major clinical problem in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD)

Urinary tract infections
Septicemia
Other opportunistic infections

Resistant to most antibiotics

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7
Q

*diseases associated with Burkholderia pseudomallei

A

Melioidosis

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8
Q

*diseases associated with Acinetobacter baumannii

A

sites Low virulence but implicated in community acquired and nosocomial infections
Recovered from numerous human sources: blood, sputum, urine, feces, vagina
Found to colonize 45% of inpatient tracheostomy

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9
Q

*diseases associated with Elizabethkingia meningoseptica

A

Pathogenic for premature infants
Associated with neonatal meningitis
Epidemics may occur in nurseries
Nosocomial outbreaks traced to breast pumps used in hospital nurseries
Mortality rate as high as 55%
May cause pneumonia in adults usually in IC patients

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10
Q

*Name Non-Fermenting bacteria that are listed as potential bioterrorist agents

A

Burkholderia pseudomallei (category B- highly virulent, no immunity in US, aerosol release)

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11
Q

characteristics of Glucose Non-Fermenting 
Gram-Negative Bacilli

A 
Gram‑negative, nonsporeforming bacteria, may be rods, or coccobacilli 
Obligate aerobes
Good growth usually seen in 24 h 
Glucose not fermented
Natural Habitat:  water, soil, plants
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12
Q

characteristics of Pseudomonas aeruginosa

A 
Aerobic Gram negative rod
Motile with polar flagella
Mucoid polysaccharide slime layer
Pili on cell surface
-Grows on blood and MacConkey agar producing spready colonies with a metallic sheen
  • Identification
  • Glucose Non-Fermenter
  • Oxidase positive
  • Grape-like odor
  • Produces Pyocyanin
  • Grows at 42oC (rare that a bacteria would grow at that high of a temp)
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13
Q

Exotoxin A

A

Correlates with virulence
Blocks protein synthesis much like diphtheria toxin
Most likely contributes to dermatonecrosis in wounds and tissue damage in lungs

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14
Q

Exoenzyme S

A

ADP-ribosylating toxin

Epithelial cell damage facilitates bacterial spread, tissue invasion and necrosis

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15
Q

Elastase

A

Results in tissue destruction and hemorrhagic lesions (ecthyma gangrenosum)
Two enzymes: Las A and Las B act synergistically to degrade elastin
Degrades compliment components and inhibits neutrophil chemotaxis and function

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16
Q

Pseudomonas types of infections

A 
skin 
lung 
urinary
ear
eye
bacteremia 
endocarditis (tricuspid valve)
osteomyelitis 
Bacteremia with ecthyma gangrenosum
17
Q

Bacteremia with ecthyma gangrenosum

A

EG is a well-recognized but uncommoncutaneous infection most often associated with a Pseudomonas aeruginosa bacteremia.

EG usually occurs in patients who are critically ill and immunocompromised and is almost always a sign of pseudomonalsepsis.

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

The transformation of an early lesion to a necrotic ulcer may occur in as little as 12 h

18
Q

pyocyanin

A

blue pigment produced by Pseudomonas aeruginosa that turns the agar blue.

p. aeruginosa also produces pyoveridin which is yellow (flourecent under UV light) therefore the agar appears green

19
Q

Treatment of Pseudomonas Infections

A

Resistant to many of the common antibiotics used for Gram negative infections

Resistance due to changes in porins

Combination therapy of cell wall active agent + aminoglycoside for serious systemic infections

20
Q

A gram-negative rod grows as a colorless colony on a MacConkey agar plate. Further laboratory testing shows the organism is oxidase positive, does not ferment glucose, produces a sweet grape-like odor and grows at 420C. Which of the following clinical infections is most likely to be caused by this organism?

Ear infection after swimming in a fresh water lake
Melioidosis
Community acquired urinary tract infection
Community acquired pneumoniae
Gastroenteritis following ingestion of contaminated water

A

Ear infection after swimming in a fresh water lake

21
Q

where is Burkholderia pseudomallei found

A

Habitat: soil, water, vegetation of S.E. Asia, 20o north and south of equator.
Primarily found in India, Thailand, Vietnam, northern Australia. Also endemic in China, Taiwan, Laos

22
Q

Melioidosis

A

caused by Burkholderia pseudomallei

  • Acute Disease: septicemia with metastatic lesions. 95% mortality if untreated
  • Subacute Disease: most common. TB like pneumonia with cellulitis and lymphangitis
  • Chronic Disease: localized chronic cellulitis. Treat with antibiotics before draining otherwise become bacteremic
23
Q

What is a pulmonary exacerbation?

A

Chronic infection leads to intermittent pulmonary exacerbations
Exacerbation characterized by recruitment of neutrophils, cytokine release, and high level of neutrophil derived elastases causing significant lung pathology.

24
Q

Stenotrophomonas maltophilia treatment

A

Drug of choice is trimethoprim-sulfamethoxazole (SXT)

inherently resistant to beta lactam agents

25
Q

Elizabethkingia meningoseptica treatment

A

Susceptibility: Very Resistant
Inherently resistant to beta lactam agents and aminoglycosides
Current methods unreliable

Drugs of choice are minocycline, rifampin, SXT, and quinolones

26
Q


Acinetobacter baumannii identification

A

Coccobacilli on Gram stain
Good growth on BAP and MacConkey
Oxidase negative
Non-motile

27
Q

Acinetobacter baumannii treatment

A 
Imipenem or meropenem
Fluoroquinolone + amikacin or ceftazidime
Ampicillin-sulbactam
Colistin
Resistance rates increasing
28
Q

A gram-negative rod was recovered from the CSF of a newborn with meningitis. It was an oxidase-positive, glucose non-fermenting rod, that failed to grow on MacConkey agar and was indole-positive. An epidemiologic investigation revealed that the mother was using a breast pump that belong to the hospital nursery and may have been the source of the causative agent. What is the likely agent of meningitis in this case.

A

Elizabethkingia meningoseptica

29
Q

Elizabethkingia meningoseptica identifying characteristics

A

Oxidase Positive
Pale yellow pigment on BAP
Poor growth on MacConkey

MHD #3 (11 decks)

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