BacterTube™ Simmons Citrate Agar

The test medium used to assess the ability of organisms to utilize citrate as their sole carbon source.
Code: 08032
Packaging: 50 tubes/ box or as per customer request.
Storage Conditions: 2–8°C.
Transportation: Ambient temperature.
Shelf Life: 6 months from the date of manufacture.

INTENDED USE

BacterTube™ Simmons Citrate Agar is used for the differentiation between Enterobacteriaceae and the members of aerogenes group on the basis of citrate utilization as sole carbon source by IMViC tests.

PRINCIPLES

The citrate medium was initially developed by Koser, containing ammonium salts as the sole nitrogen source and citrate as the sole carbon source, to differentiate Escherichia coli and Enterobacter aerogenes using IMViC tests. Later, Simmons modified Koser’s formulation by adding agar and the pH indicator bromothymol blue. This medium is recommended by APHA.
In this medium, ammonium dihydrogen phosphate and sodium citrate serve as the sole nitrogen and carbon sources, respectively. Microorganisms utilize inorganic ammonium salts as their nitrogen source, and the metabolism of these salts causes the medium to become alkaline, indicated by a color change of the pH indicator bromothymol blue from green to blue.

Allow the BacterTube™ Simmons Citrate Agar medium tubes to reach room temperature.
Sample Collection: Use a sterile straight inoculating needle to touch a bacterial colony that has been cultured for 18 – 24 hours on a solid medium. Do not use liquid cultures.
Inoculation: Gently streak the bacterial colony along the slanted surface of the agar without stabbing into the medium
Incubate the inoculated tubes at 35 – 37°C for up to 7 daysmunder aerobic conditions

RESULTS

Observe the results and interpret as per the color change:
- Positive reaction: The green color of the medium changes to blue, indicating the organism can utilize citrate as a carbon source.
- Negative reaction: The green color of the medium remains unchanged, indicating the organism cannot utilize citrate.

BacterLab ensures the quality of each product batch by testing with ATCC reference strains.

Reference strain	Incubation conditions	Expected result
Klebsiella aerogenes ATCC 13048	18 – 24 hours at 35 – 37⁰C, aerobic	Good growth, medium turns blue
Escherichia coli ATCC 25922		Inhibited, no color change
Salmonella Typhimurium ATCC 14028		Good growth, medium turns blue
Salmonella Enteritidis ATCC 13076		Good growth, medium turns blue

For 1 liter of medium

Sodium Chloride (NaCl)	5,0 g
Sodium Citrate (dehydrate)	2,0 g
Ammonium Dihydrogen Phosphate	1,0 g
Dipotassium Phosphate	1,0 g
Magnesium Sulfate (heptahydrate)	0,2 g
Bromothymol Blue	0,08 g
Agar	15,0 g