Liofilchem™ Arginine Decarboxylase Test, 30 Tests

The Arginine Decarboxylase Test is a rapid diagnostic tool used for the identification and differentiation of Enterobacteriaceae and other gram-negative bacteria, based on their ability to decarboxylate arginine into putrescine. The test supports preliminary identification in clinical microbiology, requiring further confirmatory testing for a complete diagnosis.

Principle of the Test

The test detects the enzyme arginine decarboxylase, which removes the carboxyl group from arginine, forming putrescine. This biochemical reaction results in a pH change, visualized through a color change in the medium:

1. Glucose fermentation acidifies the medium (purple → yellow).
2. If arginine decarboxylase is present, alkaline putrescine is produced, shifting the medium back to purple.
3. Positive result: Purple color
4. Negative result: Yellow color
5. No fermentation: Minimal or no color change

Kit Contents

• 30 pre-dosed tubes containing dehydrated reagents:
  • Arginine
  • Glucose
  • Bromocresol purple (pH indicator)
  • Pyridoxal (enzyme cofactor)

Required but Not Provided

• Physiological saline (0.85%)
• Inoculating loop
• Sterile mineral oil (vaseline)
• Incubator (35 ± 2 °C)
• Pipettes and quality control organisms

Test Procedure

1. Bring test tubes to room temperature.
2. Add 0.3 mL of physiological solution to each tube.
3. Inoculate with test organism from a fresh overnight culture.
4. Overlay with 2–3 drops of sterile mineral oil.
5. Incubate at 35 ± 2 °C with caps tightened, up to 96 hours.
6. Observe and interpret color changes after 4 hours, and daily thereafter.

Result Interpretation

Performance & QC Strains

Storage & Stability

• Store test tubes at 2–8 °C in original packaging
• Avoid heat and light exposure
• Shelf life: 1 year from manufacturing date
• Do not use if tubes show signs of contamination or degradation

Warnings & Precautions

• For in vitro diagnostic use only
• Use by trained professionals in microbiology labs
• Read instructions carefully before use
• Use protective equipment (gloves, goggles, lab coat)
• Do not reuse tubes or mix reagents from different batches
• Dispose of used tubes according to biohazard waste regulations

Limitations

• A heavy inoculum may be required for early positivity (4 h)
• Reading results before 12–18 h may cause false negatives
• Air exposure can lead to surface alkalinization → false positives
• Not suitable for direct testing of patient specimens; use pure cultures only

Ordering Information

The Liofilchem® Arginine Decarboxylase Test offers a fast, easy-to-interpret, and reliable solution for detecting arginine decarboxylase activity in bacterial isolates. It is an essential biochemical test for labs engaged in the differentiation of Gram-negative organisms, including clinical, food, environmental, and pharmaceutical microbiology settings.