Azide Dextrose Agar (ROTHE)

Azide Dextrose Agar (ROTHE) – ADA

Selective Medium for Enterococci Detection in Water, Food, and Dairy
Catalog Number: AS-1127

Overview

Azide Dextrose Agar (ROTHE), also known as Roth’s Agar or Azide Blood Agar Base (without blood), is a highly selective solid culture medium originally developed by Rothe et al. (1954) for the isolation and enumeration of faecal streptococci / enterococci, including Streptococcus faecalis, S. faecium, and Enterococcus species.

The inclusion of sodium azide (0.02–0.04 %) strongly inhibits Gram-negative bacteria and most competing Gram-positive flora, while enterococci grow readily. Typical colonies appear small, translucent to pink-red, allowing reliable differentiation and enumeration.

Azide Dextrose Agar is widely used in water, food, and dairy microbiology, including methods aligned with ISO 7899-2 for the detection of intestinal enterococci.

Applications

• Detection and enumeration of enterococci in drinking, bathing, and waste water
  (ISO 7899-2 reference method)

• Quality-control testing of milk and dairy products

• Isolation of enterococci from foods such as meat, cheese, and vegetables

• Confirmation of enterococci following presumptive growth on
  m-Enterococcus Agar or Kanamycin-Aesculin-Azide Agar

Key Features & Benefits

• High selectivity due to sodium azide (0.02–0.04 %)

• Glucose content (0.5–1 %) enhances characteristic pink-red colony pigmentation

• Can be used with or without 5 % sterile blood
  (blood supplementation improves colony distinction)

• Established medium in European water and food microbiology protocols

Typical Composition (per litre)

• Peptone (or meat extract) – 19.5 g

• Glucose – 7.5 g

• Sodium chloride (NaCl) – 7.5 g

• Sodium azide (NaN₃) – 0.2 g

• Agar – 15.0 g

Final pH: 7.2 ± 0.2 at 25 °C

Preparation

• Suspend 47.9 g of dehydrated medium in 1 L purified water
  (manufacturer-specific)

• Heat with frequent agitation and boil for 1 minute until fully dissolved

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

• Cool to 45–50 °C

• Optional: add 5–7 % sterile defibrinated blood to prepare
  Azide Blood Agar (ROTHE)

• Pour into sterile Petri dishes

Incubation Conditions

• Temperature: 35–37 °C

• Time: 24–48 hours

• Colony morphology: 0.5–2 mm, translucent to pink-red colonies

Storage & Stability

• Dehydrated medium: Store below 25 °C, dry and protected from light

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

• Recommended use within 2–3 weeks

Safety Note

Sodium azide is highly toxic and may form explosive compounds in contact with metals.
Dispose of prepared plates and waste in accordance with laboratory safety and chemical disposal regulations.

Intended Use

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

Quality & Compliance

• Selective medium for enterococci detection and enumeration

• Suitable for ISO-aligned water and food microbiology 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