Gram negative rods id methods

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

What color is a positive nitrate reduction test?

Red

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

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

Ak/Ak (red/red)

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

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

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

A/A (yellow/yellow)

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

Deep black appears

What organisms are AK/AK on a KIA tube?

• Morganella

• Providencea

• Shigella

What organisms are AK/A on a kia tube?

• Citrobacter (Variable)

• Salmonella

• Proteus

• Edwardsiella

What organisms are A/A on a kia tube?

• e. coli

• Enterobacter

• klebsiella

What is the principle of triple sugar agar?

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

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

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

What color is a positive Indole test?

Pink

What is the principle of the methyl red test?

If the organism produces strong acids through mixed acid fermentation.

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.

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

Both turn red

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

What color is a positive citrate test?

Blue (alkaline metabolic products present)

What is the principle of the urease test?

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

What color is a positive urease test?

Pink, ammonia produced

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

What is in the decarboxylation tubes?

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

What color is a positive decarboxylation test?

Purple

What amino acid produces cadaverine?

Lysine

What amino acid produces putrescine?

Ornithine

What amino acid produces citrulline?

Arginine

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

Yellow

What does decarboxylation mean?

Removal of a CO2 molecule

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

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

What color is a positive PDA test?

Green (phenylpyrivic acid + ferric chloride)

What does test are in the MIO agar?

• mobility

• Indole

• Ornithine

How is a MIO test read?

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

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

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

What does a LIA tube contain?

• Ferric ammonium citrate and sodium thiosulfate

• bromocresol purple

• glucose/dextrose

• lysine

If lysine is deaminated what color is the LIA tube?

Red color on slant

If lysine is decarboxylatde was color is the LIA tube?

Purple color in the butt

If glucose is used what color is the LIA?

Yellow

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

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

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

(purple/purple), lysine decarboxylase positive

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

Red/yellow. Lysine deaminase positive

What are the IMViC reactions?

• indole

• methyl red

• Voges-Proskauer

• Citrate

What are the mixed acid in the MR test?

Lactic, acetic and formic

What are the neutral products of VP?

Ethyl alcohol, acetoin, and butanediol

Which enterics are PDA positive?

• proteus

• providencia

• morganella

Which enterics are H2S positive?

• edwardsiella tarda

• Salmonella

• Proteus

• citrobacter

Which enterics are VP positive?

• klebsiella

• enterobacter

• serratia