ANTIMICROBIAL ACTIVITY OF ESSENTIAL OILS AGAINST Bacillus cereus

Pathogenic spore-forming bacteria have been a major problem for the food industry. Therefore, studying substances that are able to inhibit the growth of these bacteria is relevant as an alternative for their control. In this context, the aim of this study was to evaluate the inhibitory effect of essential oils (EOs) of cinnamon (EOC), marjoram (EOM), pink pepper (EOPR), ginger (EOG), lemon (EOL), rosemary (EOA) and white thyme (EOT) against emetic (NCTC 11143) and diarrheal (NCTC 11145) strains of Bacillus cereus. Minimum inhibitory concentration (MIC) analyses were carried out on vegetative cells and spores and minimum bactericidal concentration (MBC) was performed on vegetative cells. The MIC for vegetative cells varied from 25 to 100 mg/mL for EOL and EOG, which were the least efficient for both strains. The other EOs had MICs ranging from 0.1 to 12.5 mg/mL, especially EOC, that showed inhibition at 0.1mg/mL for both strains. The CBM for emetic strain ranged from 0.1 to 100mg/mL, and OEC showed the lowest concentration, while for diarrheal strain the variation was from 0.1 to 50 mg/mL, and EOL had highest concentration. Regarding the MIC of the spores, EOC and EOM were tested on both strains, showing the same inhibition concentration, 0.39 mg/mL; while EOT was only tested on diarrheal strain, with inhibition at 0.39 mg/mL, EOG was only tested on emetic strain, with inhibition at 1.56 mg/mL. In conclusion, the EOs can be used to inhibit growth of vegetative cells and spore germination of emetic and diarrheal strains of B. cereus, even in low concentrations.. In addition, these preliminary results indicate emetic strain is more resistant to EO than diarrheal strain.