Azide Dextrose Agar (ROTHE) – ADA 
CAT No: AS‑1127
Selective Medium for Enterococci Detection in Water, Food, and Dairy (ISO 7899‑2 Compliant)
 
Overview
Azide Dextrose Agar (ROTHE), also known as Roth’s Agar or Azide Blood Agar Base (without blood), is a highly selective solid medium developed by Rothe et al. (1954) for the isolation and enumeration of faecal streptococci / enterococci (Streptococcus faecalis, S. faecium, Enterococcus spp.) from water, food, milk, and clinical samples.
The inclusion of sodium azide (0.02–0.04%) strongly inhibits Gram‑negative bacteria and most Gram‑positive organisms, while enterococci grow luxuriantly, producing small, translucent to pink‑red colonies that are easily distinguished.
 
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 (meat, cheese, vegetables)
Confirmation of enterococci after presumptive growth on m‑Enterococcus Agar or Kanamycin‑Aesculin‑Azide Agar
 
Key Features & Benefits
High selectivity due to sodium azide (0.02–0.04%)
Addition of 0.5–1% glucose enhances colony pigmentation (pink‑red)
Can be used with or without 5% sterile blood (blood improves colony distinction)
Standard medium in European water and food microbiology protocols
 
Typical Composition (per liter)
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 Instructions
Suspend 47.9 g dehydrated medium in 1 L purified water (manufacturer‑specific).
Heat with frequent agitation; boil for 1 minute until dissolved.
Do not autoclave (sodium azide is heat‑labile and toxic).
Cool to 45–50 °C.
Optional: add 5–7% sterile defibrinated blood for Azide Blood Agar (ROTHE).
Pour into sterile Petri plates.
 
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; use within 2–3 weeks
 
Safety Note
Sodium azide is highly toxic and can form explosive compounds with metals.
Dispose of plates properly according to laboratory safety protocols.
 
Intended Use
For laboratory and water/food microbiology use only. Not for diagnostic or therapeutic applications without proper validation.