Y. enterocolitica Millichrome^™ plus Agar Base

Y. enterocolitica Millichrome plus Agar Base is a selective media for the detection of Y. enterocolitica. The distinguishing feature of these media is the inclusion of a chromogenic substrate mix that produces visible color changes upon the enzymatic activity of Y. enterocolitica.{TM="Millichrome"] chromogenic media is a specialized type of culture medium used to detect and isolate specific groups of bacteria based on their ability to produce enzymes with chromogenic substrates. The cleavage of the substrate by specific enzymes in the target microorganism releases the chromophore and thus colors the growing microbial colonies. Hence, using chromogenic agars can eliminate the need for subcultures and provide presumptive identification of a chosen microorganism. This approach shortens the turnaround time for microbial diagnosis, reduces the analytical workload, and generates cost savings relative to conventional methods for the isolation and identification of bacterial pathogens

Y. enterocolitica Millichrome plus Agar Base is a selective chromogenic culture medium intended for use in the qualitative direct detection, differentiation, and presumptive identification of pathogenic biotypes of Yersinia enterocolitica from various samples

Step 1 (Preparation of 1L Y. enterocolitica Millichrome^™ plus Agar Base)

• Disperse slowly 41.3 g of powder base in 1 L of purified water.
• Stir until agar is well thickened.
• Heat and bring to boil (100 °C) while swirling or stirring regularly. DO NOT HEAT TO MORE THAN 100 °C. DO NOT AUTOCLAVE AT 121 °C.

Warning 1: If using an autoclave, do so without pressure. Advice 1: For the 100 °C heating step, mixture may also be brought to a boil in a microwave oven: after initial boiling, remove from oven, stir gently, then return to oven for short repeated bursts of heating until complete fusion of the agar grains has taken place (large bubbles replacing foam).

• Cool in a water bath to 45-50 °C +/- 2 °C.
• Step 2 (Preparation of the Y. enterocolitica Millichrome^™ plus Supplement)
• Prepare a stock solution of the supplement: Add 100 mg to 1 mL of purified water.
• Swirl well until complete dissolution. Filter sterilize at 0.45 μm.

Warning 2: This supplement stock solution should be used immediately after Preparation, or can be stored at -20 °C and used within 15 days.
Step 3 (Mixing of the prepared base and the prepared supplement)

• Add 1 mL of the prepared supplement solution to the prepared base cooled at 45-50 °C +/- 2 °C.
• Swirl gently to homogenize.
• Pour into sterile Petri dishes.
• Let it solidify and dry.

The pathogenic Y. enterocolitica colonies are colored mauve after 48 h of incubation at an optimal growth temperature of 28°C, whereas nonpathogenic strains of the species and occasional isolates of other Enterobacteriaceae grow as metallic blue colonies after as little as 24 h of incubation at the same temperature

MilliChrome is a trademark of Merck KGaA, Darmstadt, Germany