Fig. 1. Colonies of B. cereus grown on MYP are pink and lecithinase positive, but other bacteria are not inhibited and can interfere with isolation of B. cereus. Colonies of B. cereus grown on Bacara are pink-orange and are lecithinase positive, but other organisms are inhibited.
This test may be omitted if primary inoculation media was Bacara or test results were clear-cut with original MYP agar plates and there was no interference from other microorganisms.. Mark bottom of a plate into six equal sections with felt marking pen, and label each section with sample number. Inoculate premarked 4 cm sq area of MYP agar plate by gently touching surface of agar with 2 mm loopful of culture. Allow inoculum to be fully absorbed before incubating for 24 h at 30°C. Check plates for lecithinase production as indicated by zone of precipitation surrounding growth. Mannitol is not fermented by isolate if growth and surrounding medium are eosin pink. (Yellow color indicates that acid is produced from mannitol.) B. cereus colonies are usually