Arginine Decarboxylase Broth

Arginine Decarboxylase Broth

Differential Medium for Arginine Decarboxylation Testing
Catalog Number: AS-1123

Overview

Arginine Decarboxylase Broth is a differential liquid medium used to detect the ability of Enterobacteriaceae and other bacteria to decarboxylate the amino acid L-arginine under anaerobic conditions. Decarboxylation of arginine produces alkaline amines (agmatine and putrescine), resulting in a characteristic pH shift from acidic to alkaline following initial glucose fermentation.

The medium contains bromcresol purple as a pH indicator. After an initial acid phase (yellow), organisms possessing arginine decarboxylase cause re-alkalinisation of the medium, producing a violet or purple colour. The test is performed under anaerobic conditions created by overlaying the inoculated broth with sterile mineral oil.

Arginine Decarboxylase Broth is part of classical biochemical identification schemes related to the IMViC system and is widely used in laboratory workflows for the differentiation and characterisation of Gram-negative bacteria.

Applications

• Biochemical characterisation of Enterobacteriaceae

• Differentiation of Klebsiella and Enterobacter (positive) from Escherichia coli (negative)

• Confirmation of reactions in Salmonella, Citrobacter, Proteus, Serratia, and Yersinia

• Use in standard biochemical test batteries and identification workflows

Key Features & Benefits

• Detects arginine decarboxylase activity via pH change

• Bromcresol purple indicator provides clear visual interpretation

• Requires anaerobic conditions for correct reaction expression

• Classical, well-established biochemical test medium

Principle of the Medium

Glucose fermentation initially lowers the pH of the medium, turning the indicator yellow. Under anaerobic conditions, bacteria capable of arginine decarboxylation convert arginine into alkaline amines, causing the pH to rise and the indicator to return to a violet or purple colour. Organisms lacking arginine decarboxylase remain acidic and yellow.

Composition (per litre)

• L-Arginine hydrochloride – 5.0 g

• Peptone (or meat extract) – 5.0 g

• Glucose – 0.5 g

• Bromcresol Purple – 0.02 g

• Pyridoxal phosphate – 0.005 g (optional; enhances reaction)

Final pH: 6.0 ± 0.2 at 25 °C

Preparation

• Dissolve peptone, L-arginine hydrochloride, and glucose in 990 mL distilled water

• Adjust pH to 6.0

• Add 10 mL of 0.2 % bromcresol purple solution

• Make up to 1 L with distilled water

• Dispense 3–5 mL into small tubes (approximately 10 × 100 mm)

• Sterilise by autoclaving at 121 °C for 15 minutes

Inoculation & Interpretation

• Inoculate heavily with a fresh bacterial culture

• Overlay with 5–10 mm sterile mineral oil or paraffin to ensure anaerobic conditions

• Incubate at 35–37 °C for up to 4 days

Interpretation:

• Yellow throughout: Negative (no arginine decarboxylation)

• Violet/alkaline under oil: Positive (arginine decarboxylase present)

• Yellow initially, turning purple after 24–48 h: Typical positive reaction

Storage & Stability

• Prepared tubes: Store at 2–8 °C, protected from light

• Shelf life: Use within 3 months

Intended Use

For laboratory identification and biochemical characterisation use only.
Not for direct clinical diagnostic use.

Quality & Compliance

• Classical biochemical test medium for amino acid decarboxylation

• Manufactured under controlled conditions for consistency

• Suitable for research, teaching, and method-development laboratories

Customs & Trade Information

HS / AHECC Code: 3821.00.00
Prepared culture media for development or maintenance of microorganisms