Olive oil polyphenol extract inhibits vegetative cells of Bacillus cereus isolated from raw milk

摘要

This study was conducted to analyze the antibacterialeffect of olive oil polyphenol extract (OOPE)against vegetative cells of Bacillus cereus isolatedfrom raw milk and reveal the possible antibacterialmechanism. The diameter of inhibition zone, minimuminhibitory concentration, minimum bactericidalconcentration, and survival counts of bacterial cells insterile normal saline and pasteurized milk were usedto evaluate the antibacterial activity of OOPE againstB. cereus vegetative cells. The changes in intracellularATP concentration, cell membrane potential, contentof bacterial protein, and cell morphology were analyzedto reveal possible mechanisms of action. Our resultsshowed the diameter of inhibition zone, minimum inhibitoryconcentration, and minimum bactericidal concentrationof OOPE against B. cereus vegetative cellswere 18.44 ± 0.55 mm, 0.625 mg/mL, and 1.25 mg/mL,respectively. Bacillus cereus GF-1 vegetative cells weredecreased to undetectable levels from about 8 log cfu/mL after treatments with 0.625 mg/mL of OOPE innormal saline at 30°C for 3 h and in pasteurized milk at30°C for 10 h. The antibacterial mechanisms of OOPEagainst B. cereus GF-1 vegetative cells may be due tothe reduction of intracellular ATP concentrations, cellmembrane depolarization, decrease of bacterial proteincontent, and leakage from cytoplasm. These findingsillustrated that OOPE could be used to prevent thegrowth of contaminating B. cereus cells in dairy products.