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M5 Non-Fermenting GNB Flashcards

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1
Q

What are the general characteristics of non-fermenting gram negative bacilli (4)?

A
  1. Do not ferment glucose
  2. May or may not utilize glucose by oxidization.
  3. Oxidative metabolism.
  4. Some grow rapidly and most grow on MAC.
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2
Q

What is the most common genera for Non-fermenting GNB?

A

Pseudomonas spp.

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3
Q

What kind of environment does Psuedomonas spp. really like?

A

Moisture rich environments –> moisture loving.

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4
Q

What is the clinical significance of Pseudomonas aeruginosa (9)?

A
  1. Superficial skin infections
  2. Nail infections
  3. Ear infections - Otitis media, swimmers ear (externa)
  4. Eye infections
  5. Burn infections
  6. Osteomyelitis
  7. UTIs.
  8. Respiratory infections
  9. Sepsis.
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5
Q

What type of infections are caused by Pseudomonas aeruginosa in Cystic Fibrosis (CF) patients?

A
  • Chronic infections
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6
Q

What does Pseudomonas aeruginosa do in CF patients (3)?

A

Pseudomonas aeruginosa causes biofilm formation:
1. ExoPolysaccharide polymer (alginate) - protects from adversity and enhances adhesion.
2. CF patients produce a thick & sticky bronchial secretion because of stasis of the lungs.
3. Mucin layer is resistant to antibiotics.

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7
Q

What virulence factors does Pseudomonas aeruginosa have?

A
  1. Pilli (attachment)
  2. ExoPolysaccharide polymer (Alginate) protects it from adversity and adhesion - antiphagocytic
  3. Pigments
  4. Extracellular products
    a) Hemolysins
    b) Pigments
    c) Exotoxins (shock)
    d) Proteases

Also it’s flagellum make it very motile.

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8
Q

What is the clinical significance of Pseudomonas fluorescens/putida/stutzeri?

A
  1. Patients in hospital with underlying disease
  2. They can cause infections on many sites but their significance has to be questioned and discussed
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9
Q

Are Pseudomonas fluorescens/ putida/stutzeri part of the normal human flora? If not, what?

A

Environmental, not part of the human normal flora

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10
Q

How are infections from Pseudomonas fluorescens/ putida/stutzeri transmitted? Virulence factors?

A
  1. Transmitted through medical devices & solutions
  2. Unknown virulence factors
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11
Q

What is the normal habitat of Acinetobacter spp.?

A

Environmental organism, and sometimes part of human normal flora

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12
Q

What is the clinical significance of Acinetobacter spp.?

A
  1. Opportunistic pathogen
  2. Nosocomial
  3. Ventilator acquired pneumonia
  4. Implicated in postwar infections “Iraqibacter”
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13
Q

What makes Acinetobacter spp. difficult to deal with in the hospital?

A
  1. Survives for a long period of time
  2. Resistant to antibiotics, drying, and disinfection
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14
Q

How does Acinetobacter spp. look like on BA and a gram stain?

A
  1. Purplish hue on BA, large healthy colonies
  2. “tricky” on Gram: plump cocco-bacilli (diplo-cocci-like) and sometimes underde-colorized
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15
Q

What divides the different Acinetobacter species in the lab?

A

Species divided based on saccharolytic or asaccharolytic

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16
Q

What is the clinical significance of Stenotrophomonas maltophilia?

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A
  1. Nosocomial
    a) Must correlate with clinical symptoms
    b) Exogenous spread through ventilators
    c) Immunosuppressed at increased risk
  2. Broad ranges of infections including ocular, UTI, vascular, skin, mostly respiratory.
17
Q

Is Burkholderia cepacia typically pathogenic and where is it normally found in general?

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A

Burkholderia cepacia:
1. Generally non-pathogenic
2. Environmental, not normal flora

18
Q

What disease does B. pseudomallei cause?

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A

B. pseudomallei:

Causes “melioidosis”
presents usually as a pneumonia and spreads systemically to other organs resulting in abscess formation

19
Q

What level of lab should work with B. pseudomallei?

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A

Level 3/Risk Group 3
“A pathogen that usually causes serious human or animal disease but usually not spread by casual contact. These organisms have a high individual risk but low community risk”

20
Q

From what patients is Burkholderia cepacia may be isolated from?

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A
  1. Often isolated from CF
  2. Occasionally UTI’s and respiratory infections
21
Q

What non-fermenting GNB bacteria can be found in diabetic ulcers?

Study These Flashcards
A

Alcaligenes faecalis

22
Q

What are some of the unique characteristics of Alcaligenes faecalis?

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A
  1. “Fruity odor” on BA
  2. Nitrate reduction – (NEG)
  3. Asaccharolytic (incapable of hydrolyzing or breaking down sugar molecules)
  4. O/F = -/-
23
Q

What is the clinical significance of Achromobacter xylosoxidans/denitrificans?

Study These Flashcards
A

Nosocomial septicemia & others in compromised patients

24
Q

What are the nitrate reduction and O/F results expected for Achromobacter xylosoxidans/denitrificans?

Study These Flashcards
A

Nitrate reduction +
O/F = +/-

25
What results are expected Pseudomonas aeruginosa in terms of gram, BA morphology, oxidase, TSI and O/F tests?
1. Gram: G-b 2. BA: Green pigment, Metallic sheen. Fruity smell 3. Oxidase + 4. TSI K/NC 5. O/F +/-
26
What non-fermenting organisms looks like a lavender-green-yellowish (not at 24 h), Fried egg, with an “ammonia” odor on blood agar (BA)?
Stenotrophomonas maltophilia
27
What are the results for MAC, oxidase, and DNase for Stenotrophomonas maltophilia?
MAC - NLF Oxidase negative! DNase +
28
What non fermenting organisms has colony morphology with a slightly raised appearance with a dirt like odor on blood agar (BA)?
Burkholderia cepacia
29
What is the gram, oxidase, and lysine results for Burkholderia cepacia?
G-b Weak oxidase positive Lysine decarboxylase +
30
For Burkholderia cepacia what needs to be used because it is weakly oxidase positive?
Need to use Tetramethylphenyldiaminedihydrochloride
31
What is the principle of the O/F (Oxidative/Fermentative) Test?
Media contains a high concentration of carbohydrate (dextrose, maltose, glucose, etc.) relative to peptones. Organisms ability to ferment or oxidize carbohydrates can be determined.
32
What is the procedure for the O/F test?
1. Pick a colony from a 24 hour culture plate and inoculate 2 OF medium with a straight stab almost to the bottom of tube followed by a BA ck plate. 2. Leave cap loose on 1 of the tubes. 3. Cover one tube from the pair of inoculated tubes with a 1 cm layer of sterile mineral oil and tighten cap. 4. Incubate both tubes at 35C in ambient air up to 5 days depending on the organism.
33
What are the O/F Tube results for oxidative, fermentative, and nonsaccharolytic?
Interpretation: Oxidative: opened tube acid (yellow); closed tube alkaline (green) Fermentative: opened tube acid (yellow); closed tube acid (yellow) Nonsaccharolytic: opened tube alkaline (green or blue); closed tube alkaline (green or blue). Organisms do not use the carbohydrate oxidatively or fermentatively (inert).
34
What is the limitations with the O/F test for organisms such as Pseudomonas, Stenotrophomonas, or Burkholderia?
Incubation should be at 30°C. These organisms are more active at lower temperature.
35
What is the principle of the growth at 42C test and what is the main purpose of the test?
1. Determine the ability of an organism to grow at 42°C 2. Differentiates Pseudomonas spp. (aeruginosa grows at 42°C, others do not) Positive = Pseudomonas aeruginosa ATCC 10145 Negative = E coli It can be done on agar or broth (see growth or turbidity)
36
What is the principle of the Gelatin Liquefaction test and how is it performed?
1. Determine the presence of the proteolytic enzyme gelatinase that liquefies gelatin. 2. Incubate, then refrigerate, and read: Positive = liquefaction of solidified media Negative = complete solidification of media
37
What organism is Gelatinase positive?
Pseudomonas fluorescens

Microbiology (13 decks)

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