BACTERICIDAL ACTIVITY OF CARVACROL TOWARDS THE FOOD-BORNE PATHOGEN BACILLUS-CEREUS

Carvacrol, a natural plant constituent occurring in oregano and thyme, was investigated for its bactericidal effect towards the foodborne pa thogen Bacillus cereus. Carvacrol showed a dose-related growth inhibit ion of B. cereus. At concentrations of 0.75 mmol l(-1) and above, tota l inhibition of the growth was observed. Below this concentration, car vacrol extended the lag-phase, reduced the specific growth rate and re duced the maximum population density. Incubation for 40 min in the pre sence of 0.75-3 mmol l(-1) carvacrol decreased the number of viable ce lls of B. cereus exponentially. Spores were found to be approximately 2.3-fold less sensitive to carvacrol than vegetative cells. Bacillus c ereus cells showed reduced susceptibility towards carvacrol at pH 7.0 compared with different values between pH 4.5 and 8.5. The culture and exposure temperatures had a significant influence on the survival of vegetative cells. The highest death rate of cells was observed at an e xposure temperature of 30 degrees C. Membrane fluidity was found to be an important factor influencing the bactericidal activity of carvacro l.