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Dehydrated Culture Media


A novel enrichment broth for the detection of Cronobacter (formerly E. sakazakii) from food and environmental samples. To be used in conjunction with Chromogenic Cronobacter Isolation (CCI) Agar (CM1122)

CODE: CM1121

Typical Formula*




Meat extract


Sodium chloride


Bromocresol purple

40 mg



pH 7.4 ± 0.2 @ 25°C


*Adjusted as required to meet performance standards



Vial contents: (each vial sufficient for 500ml of medium)
per vial
per litre

Dissolve 14.02g in 500ml of distilled water. Sterilize by autoclaving at 121°C for 15 minutes. Cool to approximately 50°C, and aseptically add the contents of 1 vial of Vancomycin Supplement (5mg) (SR0247E) reconstituted as directed. Mix well and aseptically dispense into sterile containers.

Cronobacter (formerly Enterobacter sakazakii) are Gram-negative rod-shaped members of the Family Enterobacteriaceae that have been implicated in outbreaks of disease in premature infants (neonates), causing sepsis, meningitis and necrotising enterocolitis. Neurological damage can be permanent, and the death rate is reported to be as high as 40-80%1.

Cronobacter spp. have been isolated at low levels from powdered infant formulae, and the organisms’ high tolerance to desiccation provides a competitive advantage in the dry environments of milk powder factories, increasing the risk of product contamination2.

The ongoing development of a new horizontal CEN-ISO standard method for the detection of Cronobacter spp by the ISO/TC 34, SC 9Ad hoc group for E. sakazakii, addresses issues such as the scope of the method, reliability of identification criteria and improvements to the media1. In anticipation of these future needs, Oxoid has launched new Cronobacter Screening Broth (CSB) (CM1121) and Chromogenic Cronobacter Isolation (CCI) Agar (CM1122).

Cronobacter Screening Broth was specifically designed by Iversen et al.3 to be used in conjunction with chromogenic media. It allows presumptive Cronobacter-positive samples to be identified before the selective plating step, and also allows Cronobacter-negative products to be released at least 24 hours earlier than with other standard methods. This is achieved by the inclusion of sucrose and the pH indicator bromocresol purple. Whilst Cronobacter spp. can ferment sucrose, most other Enterobacteriaceae, which grow as false positives on chromogenic agars, cannot. Consequently, a yellow/orange coloration in the broth after incubation (due to sucrose fermentation) indicates presumptive Cronobacter. If the broth is still purple in colour after incubation, the sample is presumed to be negative for Cronobacter.


  1. Prepare test sample in accordance with ISO 68874, ISO 82615 or the appropriate standard
  2. Homogenise x g of sample in 9 times x ml of Buffered Peptone Water ISO (CM1049)
  3. Incubate samples at 37°C ± 1°C for 18h ± 2h
  4. Transfer 0.1ml of enrichment into 10ml of CSB, and incubate at 41.5°C ± 1°C for 24h ± 2h
  5. If broth is purple, the result is negative, and no further work is required. If broth is yellow proceed to step 6.
  6. Using a 10µl loop, streak onto the surface of the CCI Agar plate
  7. Invert and incubate the plates at 41.5°C ± 1°C for 24h ± 2h
  8. Select 1-5 blue/green colonies for confirmation
  9. Streak onto Tryptone Soya Agar (CM0131) plates, and incubate at 37°C ± 1°C for 18h ± 2h
  10. Perform required biochemical confirmation tests

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label
Store the prepared medium at 2-8°C

Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Purple coloured solution

Quality Control

Positive Controls

Expected results

Cronobacter sakazakii ATCC® 12868

Turbid growth, yellow/orange colour

Cronobacter sakazakii ATCC® 29004

Turbid growth, yellow/orange colour

Cronobacter muytjensii ATCC® 51329*

Turbid growth, yellow/orange colour

Negative Controls


Escherichia coli ATCC® 25922*

Turbid growth, purple colour

Staphylococcus aureus ATCC® 25923*

Inhibited or no growth

*This organism is available as a Culti-Loop®


  1. Mullane et al. 2007. Minerva Pediatr. 59. 137-148
  2. Lai. 2001. Medicine. 80. 113-122
  3. Iversen et al. 2008. Appl. Environ. Microbiol. 74, 2550-2552
  4. ISO 6887-1:1999 Microbiology of food and animal feeding stuffs -- Preparation of test samples, initial suspension and decimal dilutions for microbiological examination.
  5. ISO 8261:2001 Milk and milk products -- General guidance for the preparation of test samples, initial suspensions and decimal dilutions for microbiological examination
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