Enterobacter Sakazakii Agar (Chromocult®)
Selective medium for the detection of Enterobacter sakazakii in milk powder and powdered infant formula.

EMD Cat. No. 1.00873.0500
500 g




Mode of Action Preparation
Experimental Procedure and Evaluation Quality Control
Typical Composition (g/liter) Literature
Picture/Image Ordering Information


Mode of Action
 The base in Chromocult Enterobacter sakazakii Agar allows good growth and strong color formation of E. sakazakii colonies.
The addition of inhibitors and the incubation temperature of 44°C largely reduce the growth of the majority of Gram-positive and Gram-negative accompanying flora.
By adding 5-bromo-4-chloro-3-indolyl-α-D-glucopyranoside a differentiation of α-D-glucosidase-positive and -negative bacteria is possible.
E. sakazakii is α-D-glucosidase positive and grows as blue-green colonies on this medium.

Typical Composition (g/liter)
 Peptone 6.0; sodium chloride 5.0; bile salt mixture 1.5; 5-bromo-4-chloro-3-indolyl-α-D-glucopyranoside 0.1; agar agar 12.0.

Preparation
 Suspend 24.6 in 1 liter of demin. water by heating in a boiling water bath or in flowing steam until the medium is completely dissolved. Autoclave at 121°C for 15 min. Cool to 45-50°C in a water bath, mix gently and pour about 15 mL in sterile Petri dishes.
 pH: 7.0 ± 0.2 at 25°C.
 The prepared medium is clear and slightly yellow.
The prepared plates can be stored for up to 2 weeks at +2°C to +8°C (protect from light and dehydration).

Experimental Procedure and Evaluation
 The agar plates must be dry. In the case of visible water, dry them before use (e.g. 20 min. at 55°C).
Inoculate the medium with a loopful of enrichment broth, streaking for isolation.
Incubation:
24 ± 2 hours at 44 ± 1°C.
Note: Incubation temperature has a strong influence on sensitivity and selectivity of this method. Temperatures higher than 45°C will inhibit the growth of E. sakazakii. Temperatures below 43°C will reduce inhibition of accompanying bacteria.
Results:
E. sakazakii: blue green, colonies.
Accompanying bacteria: colorless colonies.

Quality control

Test strains
 Recovery rate
 Color of colony
Enterobacter sakazakii ATCC 29544
 > 70%
 blue-green
Enterobacter sakazakii ATCC 29004
 > 70%
 blue-green
Enterobacter cloacae ATCC 29941
 not limited
 white
Proteus mirabilis ATCC 29906
 not limited
 white
Escherichia coli ATCC 11775
 not limited
 white
Enterococcus faecalis ATCC 11700
 < 0.001%
 --
Staphylococcus saprophyticus ATCC 15305
 < 0.001%
 --


Ordering Information

EMD Cat. No. Product Pack Size
1.00873.0500 Chromocult Enterobacter sakazakii 500 g
1.07228.0500 Buffered Peptone Water 500 g
1.10266.0500 Lauryl Sulfate Broth (LST) 500 g
1.06404.0500 Sodium Chloride 500 g


Literature
ASM Meeting 2005, Atlanta, USA. Comparison of three chromogenic media for detection of enterobacter sakazakii; a preliminary study. M. Manafi and Kerstin Lang, Hygiene Institute, Medical University of Vienna, 10950 Vienna/Austria, 2005.
Anti-bacteria & Anti-fungi Association academic meeting, Japan 2006
Evaluation of simple and rapid detection of E. sakazakii by using chromogenic substrate media.
Fumi Suzuki, Ken Noguchi, Rolf Ossmer, Merck Japan, 2006.

E. coli 11775
E. coli 11775		 Enterobacter sakazakii 29004
Enterobacter sakazakii 29004



© 2002 Merck KGaA, Darmstadt, Germany