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. The reaction produces alkaline amines (agmatine ? putrescine), causing a pH shift from acidic (purple) to alkaline (violet) after initial acid production from glucose. It is part of the classical IMViC-related biochemical tests and is widely used for identification of genera such as Escherichia, Klebsiella, Enterobacter, Salmonella, Citrobacter, Serratia, Proteus, and Yersinia.
Applications:
?? Identification of Enterobacteriaceae in clinical, food, and environmental microbiology
?? Differentiation of Klebsiella/Enterobacter (positive) from Escherichia coli (negative)
?? Confirmation of Salmonella, Citrobacter, and some Proteus strains
?? Included in standard biochemical test batteries (API 20E, Enterotube, etc.)
Key Features:
?? Positive reaction: violet/alkaline after 24�48 h (arginine decarboxylase present)
?? Negative reaction: remains yellow/acid (no decarboxylase)
?? Must be overlaid with sterile mineral oil to create anaerobic conditions
?? Bromcresol purple as pH indicator
Composition (per liter):
L-Arginine HCl   � 5.0 g
Peptone (or meat extract)     � 5.0 g
Glucose � 0.5 g
Bromcresol Purple (0.2 % sol.)� 10.0 mL (0.02 g)
Pyridoxal phosphate (optional, enhances reaction) � 0.005 g
Final pH: 6.0 � 0.2 at 25�C
Preparation:
Dissolve 10.5 g peptone + arginine + glucose in 990 mL distilled water.
Adjust pH to 6.0.
Add 10 mL of 0.2 % bromcresol purple solution.
Dispense 3�5 mL into small tubes (10 � 100 mm).
Autoclave at 121�C for 15 minutes.
Inoculation & Reading:
Inoculate heavily with fresh culture.
Overlay with 5�10 mm sterile mineral oil or paraffin.
Incubate at 35�37�C for up to 4 days.
Interpretation:
Yellow throughout ? negative (no decarboxylation)
Violet/alkaline layer under oil ? positive (arginine decarboxylase present)
Initial yellow ? purple after 24�48 h ? typical positive pattern
Storage:
Prepared tubes: 2�8�C, protected from light, use within 3 months.
For laboratory identification use only.