6. Confirmation of B. cereus
Pick 5 or more eosin pink, lecithinase-positive colonies from MYP agar plates and transfer to nutrient agar slants. Incubate slants 24 h at 30°C. Prepare Gram-stained smears from slants and examine microscopically. B. cereus will appear as large Gram-positive bacilli in short-to-long chains; spores are ellipsoidal, central to subterminal, and do not swell the sporangium. Transfer 3 mm loopful of culture from each slant to 13 × 100 mm tube containing 0.5 ml of sterile phosphate-buffered dilution water and suspend culture in diluent with Vortex mixer. Use suspended cultures including ATCC 14579 B. cereus and ATCC 64 Brevibacillus laterosporus as positive and negative controls respectively to inoculate the following confirmatory media: