R & F® Enterobacter sakazakii (Cronobacter) Chromogenic Plating Medium

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Colony Appearance

E. sakazakii (E.s.) appears as blue-black to blue-gray raised to domed colonies 1.0-2.0 mm in diameter with or without colorless halos after 24 h at 35°C. For greater selectivity, incubate plates at 41-42°C for 24 h. Shigella sonnei (S.s.)and Pantoea sp. (P. sp.) were the only other bacteria that produced blue-black colonies. All other bacteria will grow as white, yellow, green or transparent colored colonies. Proteus sp., Pseudomonas sp. and the Gram (+)s are inhibited. A quick and simple biochemical test on our screening medium biplate can easily distinguish, within 6 h, E.s (acid production in both) from S.s. and P. sp. (negative for both).
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Mechanism

Our medium uses two chromogens, X-α-D-glucopyranoside and X–β-D-cellobiopyranoside, to detect the enzymes α-glucosidase and β-cellobiosidase, respectively, which are produced by all E. sakazakii strains. Both substrates will produce the same colored colony in the presence of phenol red, blue-black to blue-gray. With the addition of the 3 sugars which E. sakazakii is negative coupled with the pH indicator, this bacterium produces blue-black to blue-gray colonies. Other enterics that contain the enzyme α-glucosidase and/or β-cellobiosidase and ferment one or more of the above mentioned sugars will produce green colonies. Within the enterics, this medium is 100% sensitivity. A screening medium that uses sucrose and melibiose fermentation (E. sakazakii strains are positive for both of these carbohydrates) increases the selectivity to 99%.
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Industry Types

Powdered infant foods–particularly powdered-milk based infant formulas and their ingredients; dairy products; corn, wheat and rice flours; and infant cereals

See Product Brochure, Use Protocol, SDS, Certificate of Analysis and Medium Preparation for more information about our medium.
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Advantages/Benefits

1. Highly selective/differential detection system using 7 different parameters for isolating E. sakazakii from other bacteria (100% sensitivity and 99% selectivity). No other chromogenic media comes close in having the number of differential parameters.


2. Use of two chromogens (α-D-glucopyranoside and β-D-cellobiopyranoside) identified all 79 E. sakazakiitested – no false negatives.


3. Competitors’ chromogenic media which utilize only one chromogen (α-D-glucopyranoside) as the differential trait will not isolate 7-10% of E. sakazakii strains due to a lack of or a weak α-glucosidase reaction – false negatives.


4. The rapid and convenient acid test using our screening medium biplate for preliminary confirmation, easily differentiates E. sakazakii from S. sonnei, Pantoea sp., or other blue-black colored colonies after 6 hours – saving time and costs.


5. The shelf life of prepared plates remains stable for at least 60 days, stored in the dark at 2-8°C. One bottle of plating medium powder and one box of supplements will make approximately 230 plates.


6. Listed in FDA’s BAM and can be used as one of the equivalent media in USDA/FSIS Microbiology Laboratory Guidebook.

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Publications

1. Restaino, L., E.W. Frampton, W.C. Lionberg, and R.J. Becker. 2006. A chromogenic plating medium for the isolation and identification of Enterobacter sakazakii from foods, food ingredients and environmental sources. J. Food Prot. 69: 315-322.

2. Chen et al. 2009. Evaluation of a revised U.S. Food and Drug Administration method for the detection and isolation of Enterobacter sakazakii in powdered infant formula: Precollaborative Study. J. AOAC International. 92: 862-872.

3. Restaino, L. 2010. Letter to the Editor “Development of an Improved Protocol for the Isolation and Detection of Enterobacter sakazakii (Cronobacter) from Powdered Infant Formula,” A Comment on: J. Food Prot. 73(6): 1016-1022.
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Ordering Information

M-0750

R & F® Enterobacter sakazakii (Cronobacter) Chromogenic Detection System (250 g Bottle of Powder & one Supplement Box – Makes 220-240 Plates)

M-0700

R & F® Enterobacter sakazakii Chromogenic Plating Medium (250 g Bottle)

M-0710

R & F® Enterobacter sakazakii Supplement for Plating Medium (1 Box)

M-0790

R & F® Enterobacter sakazakii Screening Medium Detection System (60 g Bottle of Powder & one Supplement Box – Makes 100-110 Plates)

M-0720

R & F® Enterobacter sakazakii Screening Medium for Preliminary Confirmation (60 g Bottle)

M-0780

R & F® Enterobacter sakazakii Supplement for Screening Medium (1 Box)

M-0760

R & F® Enterobacter sakazakii Chromogenic Prepared Plate (Minimum Order of 20 Plates – Shelf life is 60 Days)

M-0770

R & F® Enterobacter sakazakii Screening Prepared Biplate (Minimum Order of 20 Plates – Shelf life is 60 Days)