Reagents

Diverse biochemical reagents are known for determining certain metabolisms and to differentiate the bacteria.

Still often classical biochemical tests are used to determine microorganisms. The result can be seen by a color change. Most reactions are based on the detection of an enzyme with a certain given substrate. Also methods to detect certain metabolites by chemical reaction and or complex building techniques are used. At the end a color change gives a result which leads to more cognition of the unknown organism (see table 1).

Cat. No.	Detection of	Differentiation of Organisms	Reaction	Color (by positive result)	Reagent
29333 39442	acetoin production	Klebsiella, Enterobacter	oxidize acetoin, reacts with alpha-naphtol	red	Barritt's Reagent A Barritt's Reagent B
07689	acetoin production	Klebsiella, Enterobacter	oxidize acetoin, reacts with alpha-naphtol	red	O'Meara's Reagent
38497 39441	nitrate reduction to nitrite	Enterobacter, E. coli, Salmonella	reacts with sulphanilic acid, forms a azo dye with alpha-naphtylamine	red	Nitrate Reagent A Nitrate Reagent B
07345 07817	oxidase activity	oxidase positives, oxidase negatives	oxidize dimethyl-p-phenylenediamine hydrochloride, build a complex with alpha-naphtol	dark blue	Oxidase Reagent acc. Gaby-Hadley A Oxidase Reagent acc. Gaby-Hadley B
18502	oxidase activity	oxidase positives, oxidase negatives	oxidize N,N-dimethyl-p-phenylenediamine to Wurster's blue	dark blue-purple	Oxidase Reagent acc. Gordon-McLeod
08714	strong acid production	E. coli, Enterobacter	indicator reaction	red	Methyl Red Solution
80353	tryptophan deaminase activity	Proteus	reacts with indolepyruvic acid	dark brown	TDA Reagent
49825	tryptophanase activity	E. coli	reacts with indole	blue-purple	DMACA Reagent
60983 67309	tryptophanase activity	E. coli	reacts with indole	red	Kovac's Reagent for indoles Kovac's Reagent for indoles
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table 1: Biochemical Tests

Application example: Oxidase Reagents acc. Gaby-Hadley

These reagents can be used to perform the cytochrome c oxidase test in different methods. To differentiate organisms based on the presence of cytochrome c oxidase is one of the first and most important step by the identification of bacteria. The cytochrome c oxidase present in most gram negative bacteria oxidize dimethyl-p-phenylenediamine and alpha-naphtol a dark blue complex (indophenol blue). The test is applicable on agars in broths and on discs (see figure 1-4). Important is to do a positive and negative control with the samples.

Instructions:
Grow test culture on nutrient agar slant (18-24 hours). Add 2-3 loops of reagents A and B to slant.
Tilt tube to permit reagents to mix and flow over growth.

Result:
Observe for color change. A positive reaction shows a dark purple blue color on growth, especially at the border of the colonies, within 2 minutes.

Figure 1: E. coli on a agar plate	Figure 2: Pseudomonas flourescence on a agar plate
Figure 3: paper discs impregnated with 2 drops of each reagent: left disc with E. coli; right disc with Pseudomonas flourescence	Figure 4: cultures with 2 drops of each reagent: left tube with E. coli; right tube with Pseudomonas fluorescence

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