29F-3 |
Antimicrobial activity of allspice (Pimenta dioica) essential oil on the pathogenicity of Listeria monocytogenes ATCC 43256 |
D. L. BYRD, L. T. Walker, L. L. Williams, and M. Verghese. Dept. of Food & Animal Sciences, Alabama A&M Univ., PO Box 1628, Normal, AL 35762-1628 Listeria monocytogenes is a facultative anaerobic Gram-positive rod-shaped bacterium that causes the food-borne illness, listeriosis. Annually, there is an average of 2,500 reported cases of listeriosis with 500 resulting deaths in the US. It is therefore challenging to devise food preservation and treatment measures for controlling and preventing listeriosis. Recent studies indicate that herbs, spices, and plant-based essential oils (aromatic) can inhibit the growth of Gram-positive and Gram-negative food-borne bacteria, yeasts, and molds. In this research the pathogenicity of L. monocytogenes ATCC 43256 in the presence of allspice (Pimenta dioica) essential oil (AEO) was studied. The objective was to determine the minimum inhibitory concentration of AEO on the cell death rate of L. monocytogenes ATCC 43256. Aliquots (1ml) of L. monocytogenes ATCC 43256 in listeria enrichment broth (106 cfu/ml) were subcultured for 24 hours in a 24-well microtiter plate. A 100% pure sample of AEO was diluted to 10 separate concentrations ranging from 0 – 10% in increments of 1ml (0%=controls). A 100µl aliquot of each concentration was inoculated, in duplicate, into each well containing L. monocytogenes and then incubated for 6 hours. Following incubation, a 100µl sample from each well was removed and plated (Oxford media) after 2, 4, and 6 hours. The plates were incubated for 48 hours and total viable counts determined. The results showed that L. monocytogenes in controls grew exponentially (2 hrs=0; 4 hrs=6.1 x 102; 6 hrs=1.2 x 103 cfu/ml) while AEO treated samples at all concentrations showed no growth. Hence, AEO completely inhibited L. monocytogenes ATCC 43256 at 2, 4, and 6 hours of incubation. These results are significant with regards to the safety of food products as plant-based essential oils could be useful in inhibiting the survival and growth of L. monocytogenes.
Session 29F, Food Microbiology: Control of foodborne microorganisms by antimicrobials
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