Gram negative rods id methods

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47 Terms

1
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What is the principle of the nitrate reduction test?

Sulfanilic acid and alpha-naphthylamine are added to inoculated sample to detect if the organism reduces nitrate to nitrite

2
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What color is a positive nitrate reduction test?

Red

3
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What is the principle of the Kligler Iron agar (KIA) test?

1:10 ratio of glucose to lactose is used to detect and differentiate between glucose and lactose fermentation. Ferrous sulfate and Na thiosulfate is also added to detect H2S production

4
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What it the appearance of a KIA tube if no fermentation occurs?

Ak/Ak (red/red)

5
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What is the appearance of a KIA tube if only glucose fermentation occurs?

Ak/A (red (slant)/yellow (butt))

6
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What is the appearance of a KIA tube if both glucose and lactose are fermented?

A/A (yellow/yellow)

7
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If the organism produces H2S what happens to the KIA tube?

Deep black appears

8
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What organisms are AK/AK on a KIA tube?

  • Morganella

  • Providencea

  • Shigella

9
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What organisms are AK/A on a kia tube?

  • Citrobacter (Variable)

  • Salmonella

  • Proteus

  • Edwardsiella

10
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What organisms are A/A on a kia tube?

  • e. coli

  • Enterobacter

  • klebsiella

11
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What is the principle of triple sugar agar?

Similar to KIA but sugars are 1% lactose, 1% sucrose, and 0.01% glucose and peptones.

12
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What can Triple sugar agar be used to screen for and why?

Salmonella and shigella as it contains sucrose which Sal/shigella can not ferment but other enterics can

13
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What is the principle of Indole testing?

Ehrlich’s/Kovac’s reagent is added to see if the organism possesses tryptophanase, which breaks down tryptophane into indole and pyruvic acid

14
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What color is a positive Indole test?

Pink

15
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What is the principle of the methyl red test?

If the organism produces strong acids through mixed acid fermentation.

16
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What is the principle of the Voges Proskauer test?

Detects acetoin which is the end product of the butylene glycol pathway by adding KOH and alpha napthol.

17
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What colors to the MR/VP tests turn when positive?

Both turn red

18
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What is the principle of the citrate utilization test?

To see if an organism can us citrate as its sole energy source through the use of bromothymol blue

19
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What color is a positive citrate test?

Blue (alkaline metabolic products present)

20
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What is the principle of the urease test?

To see if an organism breaks down urea through the use of christensen’s agar

21
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What color is a positive urease test?

Pink, ammonia produced

22
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What is the principle of decarboxylation tests?

Testing for the organism’s ability to decarboxylate specific amino acids in anaerobic conditions by adding mineral oil over the top

23
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What is in the decarboxylation tubes?

Moellar decarboxylase medium, specific amino acid, small amount of glucose and bromocresol purple

24
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What color is a positive decarboxylation test?

Purple

25
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What amino acid produces cadaverine?

Lysine

26
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What amino acid produces putrescine?

Ornithine

27
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What amino acid produces citrulline?

Arginine

28
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If there is glucose fermentation of no decarboxylation what color is the tube?

Yellow

29
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What does decarboxylation mean?

Removal of a CO2 molecule

30
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What is the principle of the phenylalanine deaminase (PDA) test?

Test for the presence of phenylalanine deaminase which produces phenyl pyruvic acid and ammonia.

31
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What color is a positive PDA test?

Green (phenylpyrivic acid + ferric chloride)

32
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What does test are in the MIO agar?

  • mobility

  • Indole

  • Ornithine

33
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How is a MIO test read?

Agar checked for motility, purple color for ornithine decarboxylation, then indole reagent

34
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What is the principle of Lysine Iron agar (LIA)?

Used to determine if an organism can decarboxylate or deaminate lysine and form H2S.

35
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What does a LIA tube contain?

  • Ferric ammonium citrate and sodium thiosulfate

  • bromocresol purple

  • glucose/dextrose

  • lysine

36
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If lysine is deaminated what color is the LIA tube?

Red color on slant

37
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If lysine is decarboxylatde was color is the LIA tube?

Purple color in the butt

38
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If glucose is used what color is the LIA?

Yellow

39
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If the LIA tube is AK/A what does that mean?

(purple/yellow) Lysine not broken down, glucose used fermentatively, negative test

40
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If the LIA tube is AK/AK what does that mean?

(purple/purple), lysine decarboxylase positive

41
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If the LIA tube is R/A what does that mean?

Red/yellow. Lysine deaminase positive

42
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What are the IMViC reactions?

  • indole

  • methyl red

  • Voges-Proskauer

  • Citrate

43
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What are the mixed acid in the MR test?

Lactic, acetic and formic

44
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What are the neutral products of VP?

Ethyl alcohol, acetoin, and butanediol

45
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Which enterics are PDA positive?

  • proteus

  • providencia

  • morganella

46
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Which enterics are H2S positive?

  • edwardsiella tarda

  • Salmonella

  • Proteus

  • citrobacter

47
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Which enterics are VP positive?

  • klebsiella

  • enterobacter

  • serratia