HiCrome™ Escherichia coli HiCynth™ Agar

Principle And Interpretation

HiCrome™ E.coli Agar is based on Tryptone Bile Agar to detect Escherichia coli in foods (1), where recovery of E.coli is faster, more reliable and accurate. Most of the E.coli strains can be differentiated from other coliforms by the presence of enzyme glucuronidase, which is highly specific for E.coli (2). The chromogenic agent X-glucuronide used in this medium helps to detect glucuronidase activity of E.coli. E.coli cells absorb X-glucuronide and the intracellular glucuronidase enzyme splits the bond between the chromophore and the glucuronide. The released chromophore gives bluish green coloration to the E.coli colonies. This medium is recommended for isolation of E.coli from water and food samples. HiCrome™ E.coli HiCynth™ Agar is prepared by completely replacing animal based peptones and vegetable peptones with chemically defined peptones to avoid BSE/TSE risks associated with animal peptones. HiCynth™ peptone no. 2 and HiCynth™ peptone no. 5 provides carbon, nitrogen compounds, long chain amino acids, vitamins and other essential growth nutrients to the organisms. Synthetic detergent No.1 inhibits gram-positive organisms. Sodium chloride and phosphates maintain osmotic balance and buffering action respectively. The surface of the plated medium is dried before use. Dilute food samples 1:5 or 1:10 with 0.1% (w/v) sterile Peptone Water (M028) and homogenize in a blender or a stomacher. Pipette 0.5 ml or 1.0 ml of the homogenized food sample on to the plate and spread with sterile glass spreader. Incubate the plates at 30°C for 4 hours and then at 44°C for 18 hours.