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Microbiology > M5 Non-Fermenting GNB > Flashcards

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
  2. Alginate
  3. Pigments
  4. Extracellular products
    a) Hemolysins
    b) Pigments
    c) Exotoxins
    d) Proteases
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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?

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?

A

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

18
Q

What disease does B. pseudomallei cause?

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?

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?

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?

A

Alcaligenes faecalis

22
Q

What are some of the unique characteristics of Alcaligenes faecalis?

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?

A

Nosocomial septicemia & others in compromised patients

24
Q

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

A

Nitrate reduction +
O/F = +/-

25
Q

What results are expected Pseudomonas aeruginosa in terms of gram, BA morphology, oxidase, TSI and O/F tests?

A
  1. Gram: G-b
  2. BA: Green pigment, Metallic sheen. Fruity smell
  3. Oxidase +
  4. TSI K/NC
  5. O/F +/-
26
Q

What non-fermenting organisms looks like a lavender-green-yellowish (not at 24 h), Fried egg, with an “ammonia” odor on blood agar (BA)?

A

Stenotrophomonas maltophilia

27
Q

What are the results for MAC, oxidase, and DNase for Stenotrophomonas maltophilia?

A

MAC - NLF
Oxidase negative!
DNase +

28
Q

What non fermenting organisms has colony morphology with a slightly raised appearance with a dirt like odor on blood agar (BA)?

A

Burkholderia cepacia

29
Q

What is the gram, oxidase, and lysine results for Burkholderia cepacia?

A

G-b
Weak oxidase positive
Lysine decarboxylase +

30
Q

For Burkholderia cepacia what needs to be used because it is weakly oxidase positive?

A

Need to use Tetramethylphenyldiaminedihydrochloride

31
Q

What is the principle of the O/F (Oxidative/Fermentative) Test?

A

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
Q

What is the procedure for the O/F test?

A
  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
Q

What are the O/F Tube results for oxidative, fermentative, and nonsaccharolytic?

A

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
Q

What is the limitations with the O/F test for organisms such as Pseudomonas, Stenotrophomonas, or Burkholderia?

A

Incubation should be at 30°C. These organisms are more active at lower temperature.

35
Q

What is the principle of the growth at 42C test and what is the main purpose of the test?

A
  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
Q

What is the principle of the Gelatin Liquefaction test and how is it performed?

A
  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
Q

What organism is Gelatinase positive?

A

Pseudomonas fluorescens

Microbiology (13 decks)

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