What does the citrate test differentiate?

Citrate test is used to determine the ability of an organism to utilize citrate as a sole source of energy. A citrate test is performed as a part of the IMViC test to differentiate members of Enterobacteriaceae.

Why is Simmons citrate agar differential?

Simmons Citrate Agar is used as a differential medium for the identification of enteric bacteria by using Citrate as the sole source of carbon and Ammonium as the sole source of nitrogen.

What type of indicator does the citrate test use?

Simmons citrate agar contains sodium citrate as the sole source of carbon, ammonium dihydrogen phosphate as the sole source of nitrogen, other nutrients, and the pH indicator bromthymol blue. This test is part of the IMViC tests and is helpful in differentiating the Enterobacteriaceae .

What are the two types of citrate agar?

Simmons Citrate agar is used to test an organism’s ability to utilize citrate as a source of energy. Ammonium Dihydrogen Phosphate is the sole source of nitrogen. Dipotassium Phosphate acts as a buffer. Sodium Chloride maintains the osmotic balance of the medium.

Why citrate test is done?

Citrate agar is used to test an organism’s ability to utilize citrate as a source of energy. When the bacteria metabolize citrate, the ammonium salts are broken down to ammonia, which increases alkalinity. The shift in pH turns the bromthymol blue indicator in the medium from green to blue above pH 7.6.

What organism is citrate positive?

Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms. Escherichia coli and Shigella dysenteriae are citrate negative.

What is the substrate in the citrate test?

Citrate agar is used to test an organism’s ability to utilize citrate as a source of energy. The medium contains citrate as the sole carbon source and inorganic ammonium salts (NH4H2PO4) as the sole source of nitrogen.

How citrate test is performed?

Procedure of Citrate Utilization Test Streak the slant back and forth with a light inoculum picked from the center of a well-isolated colony. Incubate aerobically at 35 to 37 C for up to 4-7 days. Observe a color change from green to blue along the slant.

Is a positive citrate test acidic or alkaline?

The alkaline pH turns the pH indicator (bromthymol blue) from green to blue. This is a positive result (the tube on the right is citrate positive). Klebsiella pneumoniae and Proteus mirabilis are examples of citrate positive organisms.

What is the substrate in citrate test?

What is the substrate for the Citrate Agar? An enzyme called citrase will catabolize the citrate into oxaloacetic acid and acetic acid.

How is citrate test performed?

What is the alternative citrate test media?

Christensen developed an alternative citrate test medium that does not require the organism to use citrate as a sole carbon source. Christensen’s medium contains both peptone and cysteine. Thus citrate-negative bacteria can also grow on this medium.

What are the ingredients used in a citrate test?

Citrate test is conducted in the medium of simmon citrate agar and the mixture is prepared using the following ingredients. Sodium citrate is considered as both a carbon source and an energy source. Nitrogen source is NH 4+.

What is christchristensen’s alternative citrate test?

Christensen developed an alternative citrate test medium that does not require the organism to use citrate as a sole carbon source. Christensen’s medium contains both peptone and cysteine.

What is a positive citrate utilization test?

Some organisms are capable of growth on citrate and do not produce a color change. Growth is considered a positive citrate utilization test, even in the absence of a color change. The inoculum should be from a pure, overnight culture grown on a solid medium and not from a broth suspension.