Azide Dextrose Broth (ROTHE)

Azide Dextrose Broth (ROTHE) – ADB

Selective Enrichment Medium for Enterococci Detection in Water, Food, and Dairy
Catalog Number: AS-1128

Overview

Azide Dextrose Broth (ROTHE) is a highly selective liquid enrichment medium originally developed by Rothe et al. (1954) for the isolation and presumptive detection of faecal streptococci / enterococci, including Enterococcus faecalis, E. faecium, and E. durans, from water, milk, food, and environmental samples.

The presence of sodium azide (0.02–0.04 %) inhibits Gram-negative bacteria and most competing Gram-positive flora, while enterococci grow rapidly, producing dense turbidity within 18–24 hours at 37 °C.
Azide Dextrose Broth is specified as the official enrichment step in ISO 7899-1 and DIN 38411 prior to confirmation on bile-aesculin-azide agar or by membrane filtration methods.

Applications

• Selective enrichment of enterococci from heavily contaminated samples
  (water, sewage, milk, meat products)

• Most Probable Number (MPN) determination of faecal streptococci in water testing

• First enrichment step in ISO 7899-1 and national standards for bathing and drinking water

• Pre-enrichment prior to confirmation on
  Kanamycin-Aesculin-Azide Agar or Bile Aesculin Agar

Key Features & Benefits

• High selectivity due to sodium azide inhibition
  (typically 0.2–0.3 g/L)

• Rapid and heavy growth of enterococci with visible turbidity within 18–24 hours

• Available in single- and double-strength formats for MPN series

• Positive tubes show dense turbidity with sediment, requiring confirmatory subculture

Standard Composition (per litre – single strength)

• Peptone / meat extract – 20.0 g

• Glucose (dextrose) – 5.0 g

• Sodium chloride (NaCl) – 5.0 g

• Dipotassium phosphate (K₂HPO₄) – 2.7 g

• Monopotassium phosphate (KH₂PO₄) – 2.7 g

• Sodium azide (NaN₃) – 0.2 g

Final pH: 6.8 ± 0.2 at 25 °C

Preparation

• Dissolve 32–35 g of dehydrated medium in 1 L purified water

• Heat with frequent agitation until completely dissolved

• Do not autoclave (sodium azide is heat-labile and toxic)

• Dispense into tubes:

  • Single strength: 10 mL per tube

  • Double strength: 5 mL per tube (for MPN series)

• Sterilise by tyndallisation
  (100 °C for 30 minutes on three successive days)
  or by membrane filtration where required

Incubation Conditions

• Temperature: 35–37 °C
  (44 °C may be used for faecal streptococci confirmation)

• Time: 18–48 hours

• Positive reaction: Dense turbidity, often with sediment

Storage & Stability

• Dehydrated medium: Store at 10–30 °C, dry and protected from light

• Prepared broth: Store at 2–8 °C

• Recommended use within 4 weeks

Safety Note

Sodium azide is highly toxic and may form explosive compounds in contact with copper or lead plumbing.
Dispose of broth and contaminated materials according to laboratory chemical-safety protocols.

Intended Use

For laboratory, water, food, and environmental microbiology use only.
Not for diagnostic or therapeutic applications without appropriate validation.

Quality & Compliance

• Selective enrichment medium for enterococci

• Suitable for ISO 7899-1 and DIN-aligned workflows

• Manufactured under controlled conditions for batch consistency

Customs & Trade Information

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