STEC Millichrome^™ plus Agar Base

STEC Millichrome^™ plus Agar Base is a selective chromogenic culture medium used for the identification of Shiga-like toxin-producing E. coli (STEC). The media contains chromogenic substrates that produce visible color changes upon enzymatic activity of E. coli. Peptone and yeast extract are nitrogenous nutrients for growth and other essential growth factors. Sodium chloride provides osmotic balance. The chromogenic mix contains chromogenic substrates for color differentiation based on the ability to cleave the substrate by characteristic enzymes. STEC Millichrome^™ plus supplement contains selective agents that allow STEC to grow while other organisms are inhibited. Agar is a solidifying agent.

STEC Millichrome^™ plus Agar Base is a highly selective chromogenic culture medium intended for use in the qualitative direct detection, differentiation, and presumptive identification of Shiga-like-toxin producing E. coli (STEC) in various samples, including food products for human consumption, animal feed, and environmental samples.

Step 1 (Preparation of the base STEC Millichrome^™ plus Agar Base)

• Disperse slowly 30.8 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: 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. Swirl or stir gently to homogenize.

Step 2 (Preparation of the STEC Millichrome^™ plus Agar Base and mix with base)

• Aseptically rehydrate 1 vial with 10 mL of sterile water.
• Swirl well until complete dissolution.
• Add 1 vial rehydrated solution to 1L STEC Millichrome^™ plus Agar Base cooled at 45-50 °C.
• Swirl gently to homogenize.

Step 3 Pour plates

• Pour into sterile Petri dishes
• Let it solidify and dry.

The presence of mauve colonies indicates the presence of STEC. Other organisms may show colorless or blue colonies or be inhibited. STEC O157 is nonfluorescent under UV light, while other STEC serotypes are variable in fluorescence under the UV lamp at 365nm.

MilliChrome is a trademark of Merck KGaA, Darmstadt, Germany

The product is notintended for diagnosing infections or guiding treatment.