Arginine Dihydrolase Broth

Arginine Dihydrolase Broth

Differential Medium for Arginine Dihydrolase (ADH) Testing
Catalog Number: AS-1124

Overview

Arginine Dihydrolase Broth is a differential liquid medium used to detect the ability of non-fermentative Gram-negative rods to produce ammonia from L-arginine via the arginine dihydrolase (ADH) pathway under anaerobic conditions. Typical target organisms include Pseudomonas aeruginosa, Pseudomonas putida, Pseudomonas fluorescens, Burkholderia cepacia, Achromobacter spp., Alcaligenes spp., and Bordetella spp.

A positive reaction results in a strong alkaline shift, producing a colour change from colourless to bright purple-violet due to ammonia production. The test is performed under anaerobic conditions created by overlaying the inoculated medium with sterile mineral oil.

Arginine Dihydrolase Broth is a core component of classical identification schemes for non-enteric, oxidase-positive Gram-negative bacteria in laboratory workflows.

Applications

• Identification of Pseudomonas aeruginosa and related pseudomonads

• Differentiation of Burkholderia, Stenotrophomonas, Achromobacter, and Alcaligenes

• Part of classical identification schemes (King’s scheme, API 20NE, VITEK GNI, and related systems)

• Confirmation of oxidase-positive, non-fermentative Gram-negative isolates

Key Features & Benefits

• Detects arginine dihydrolase (ADH) activity via ammonia production

• Rapid positive reactions in Pseudomonas aeruginosa (often within 4–8 hours)

• Clear colour endpoint using bromothymol blue indicator

• Requires anaerobic conditions for correct expression of the reaction

Principle of the Medium

Under anaerobic conditions, organisms possessing the arginine dihydrolase pathway convert arginine to ammonia, resulting in alkalinisation of the medium. The pH indicator bromothymol blue responds to this increase in pH, producing a bright purple-violet colour. Organisms lacking ADH activity do not alkalinise the medium, which remains colourless or pale.

Composition (per litre)

• L-Arginine hydrochloride – 5.0 g

• Peptone – 1.0 g

• Sodium chloride (NaCl) – 5.0 g

• Dipotassium phosphate (K₂HPO₄) – 0.3 g

• Bromothymol Blue – 0.03 g

Final pH: 7.0 ± 0.2 at 25 °C

Preparation

• Dissolve peptone, sodium chloride, dipotassium phosphate, and L-arginine hydrochloride in 970 mL purified water

• Adjust pH to 7.0

• Add 30 mL of 0.1 % bromothymol blue solution

• Make up to 1 L with purified water

• Dispense 3–4 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 immediately with 5–8 mm sterile mineral oil or paraffin to ensure anaerobiosis

• Incubate at 35–37 °C

• Examine after 4 hours, 8 hours, and 24 hours
  (incubation may be extended up to 7 days for slow-reacting strains)

Interpretation:

• Bright purple-violet throughout: Positive (arginine dihydrolase present)

• Greenish or no colour change: Negative

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 non-fermentative Gram-negative bacteria

• 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