This Chromogenic Cronobacter Agar (also known as Chromogenic Enterobacter sakazakii Agar) is a dehydrated powder formulation designed for the rapid isolation and detection of Cronobacter species (formerly classified as Enterobacter sakazakii) from food and environmental samples. This medium is particularly valuable in the microbiological testing of powdered infant formula (PIF) and other dairy products, where Cronobacter contamination poses a significant health risk to neonates.
The medium contains a chromogenic substrate that is cleaved by specific Cronobacter enzymes, producing characteristic blue-green colonies. This color reaction allows presumptive identification of Cronobacter within 24 hours, reducing the need for extensive biochemical confirmation and significantly accelerating testing workflows.
Intended Use
- Rapid isolation and detection of Cronobacter species (formerly Enterobacter sakazakii).
- Microbiological testing of powdered infant formula and dairy products.
- Environmental monitoring in infant formula production facilities.
- Food safety and hygiene verification.
- Research and educational laboratory applications.
Composition (per 1000 mL, as Dehydrated Basis)
- Peptone (Casein): 15.0 g
- Soy Peptone: 5.0 g
- Sodium Chloride: 5.0 g
- Ammonium Ferric Citrate: 1.0 g
- Sodium Thiosulfate: 1.0 g
- Sodium Deoxycholate: 1.0 g
- 5-Bromo-4-chloro-3-indolyl-α-D-glucopyranoside (X-α-Glc): 0.1 g
- Agar: 15.0 g
- Final pH: 7.3 ± 0.2 at 25°C
Quality Control (Growth Performance)
Validated at 36 ± 1°C for 48 hours:
- Enterobacter sakazakii ATCC 29544 (30–100 CFU): Growth rate ≥90%; blue-green colonies.
- Salmonella typhimurium ATCC 14028 (streak): Growth; no color change.
- Escherichia coli ATCC 25922 (streak): White, colorless, or light yellow colonies.
- Staphylococcus aureus ATCC 25923 (10⁴–10⁵ CFU): Completely inhibited; no growth.
Physicochemical Properties
- Appearance: Powder – light yellow; Prepared plate – light yellow, transparent.
- Moisture (Powder): ≤5%
- Gel Strength: 550–650 g/cm²
Storage and Shelf Life
- Format: 43.1 g/bottle, dehydrated powder.
- Shelf Life: 2 years from date of manufacture (standard for dehydrated media; confirm with your supplier if different).
- Storage: Store in a dry, dark place at 2–8°C. Keep tightly closed to prevent moisture absorption.
Q: What is Chromogenic Cronobacter Agar used for?
A: It is used for the rapid isolation and detection of Cronobacter species (formerly Enterobacter sakazakii) in food and environmental samples, particularly powdered infant formula.
Q: How quickly can results be obtained?
A: Presumptive Cronobacter colonies appear blue-green after incubation at 36 ± 1°C for 24–48 hours.
Q: Why do Cronobacter colonies appear blue-green?
A: The chromogenic substrate X-α-glucopyranoside is cleaved by the α-glucosidase enzyme produced by Cronobacter, releasing a blue-green chromogen.
Q: How do I prepare the medium?
A: Weigh 43.1 g of powder, add to 1,000 mL of distilled water, heat to boiling until dissolved, autoclave at 121°C for 15 minutes, and cool to 50–55°C before pouring plates.
Q: What is the difference between Cronobacter and Enterobacter sakazakii?
A: Enterobacter sakazakii was reclassified into the genus Cronobacter in 2007. The terms are often used interchangeably in older literature.
Q: How should I dispose of the plates after use?
A: This is a single-use product. After use, plates must be disposed of as biohazardous waste. Autoclave the plates before final disposal.
