Liofilchem™ Citrate Test Kit

The Liofilchem™ Citrate Test is a rapid and reliable method for the presumptive identification of Enterobacteriaceae and non-fermenting Gram-negative bacteria. This diagnostic test is based on the organism's ability to utilize citrate as its sole carbon source and ammonium as its sole nitrogen source. It is widely used in clinical microbiology for bacterial differentiation and as part of biochemical identification workflows.

Key Features

1. Selective for Citrate Utilization:
   • Differentiates citrate-positive and citrate-negative bacteria by color change.
2. Rapid and Reliable:
   • Positive reactions can be observed as early as 4–6 hours, with final results in 18–24 hours.
3. Convenient Format:
   • Supplied in a kit containing 30 ready-to-use tubes, making it ideal for high-throughput testing.
4. Easy Interpretation:
   • Positive reaction: Blue color (alkaline pH due to citrate utilization).
   • Negative reaction: Green color (no citrate utilization).
5. Validated Performance:
   • Tested using standard QC strains, ensuring accuracy and reproducibility.

Kit Contents

• 30 tubes of Citrate Test medium, each containing lyophilized reagents (ammonium salts, citrate, bromothymol blue indicator).

Method Principle

• Bacteria capable of utilizing sodium citrate as the sole carbon source and ammonium dihydrogen phosphate as the sole nitrogen source will produce an alkaline reaction, turning the bromothymol blue indicator from green to blue.

Applications

1. Clinical Microbiology:
   • Identification of Klebsiella pneumoniae, Proteus mirabilis, and Enterobacter cloacae (citrate-positive).
   • Differentiation of Escherichia coli (citrate-negative) from other Enterobacteriaceae.
2. Research:
   • Studies on metabolic pathways involving citrate utilization in Gram-negative bacteria.
3. Quality Control:
   • Use validated control strains to ensure accuracy and reliability in diagnostic workflows.

Test Procedure

1. Prepare a bacterial suspension equivalent to 0.5 McFarland in 0.25 mL of physiological saline.
2. Add the entire suspension to a Citrate Test tube.
3. Incubate at 35 ± 2°C for 18–24 hours (positive reactions may appear in 4–6 hours).
4. Observe the color change in the suspension:
   • Positive: Blue (citrate utilized).
   • Negative: Green (no citrate utilization).

Quality Control

Storage and Shelf Life

• Storage Conditions: 2°C to 8°C, away from light.
• Shelf Life: 1 year.

Limitations

1. Luxuriant growth without a color change may indicate a false positive; repeat the test with a lighter inoculum.
2. Results alone are insufficient for species-level identification; additional biochemical tests are recommended.
3. Avoid carryover contamination from the previous medium to prevent false positives.

Warnings and Precautions

1. For in vitro diagnostic use only.
2. Handle all specimens as potentially infectious.
3. Use a light inoculum to avoid false-positive reactions due to carryover substances.
4. Do not use if the product shows signs of contamination or deterioration.

Advantages

• Rapid and Accurate: Detects citrate utilization in as little as 4–6 hours.
• Convenient Format: Ready-to-use tubes eliminate the need for media preparation.
• Reliable Results: Validated with control strains for accuracy.
• Easy-to-Interpret: Clear color change ensures straightforward results.

Packaging

Why Choose Liofilchem Citrate Test?

• Simplifies bacterial differentiation through a reliable, easy-to-use format.
• Saves time with rapid detection of citrate utilization.
• Trusted for clinical diagnostics and research applications.