The Effects of Selected Spices of Escherichia coli O157:H7 on MacConkey Sorbitol Agar and in Ground Beef

by: Tenny Jordan

During the past decade, Escherichia coli O157:H7, a strain of enterohemorrhagic E. coli, has evolved from a clinical novelty to a global public-health concern. The medicinal properties of spices have recently become a focus for testing the sensitivity of foodborne bacterial pathogens. In this experiment three spices (garlic, cinnamon, and clove) that possess antimicrobial activity were selected and it was tested whether or not they had an effect on the number of E. coli O157:H7 colonies grown on MacConkey sorbitol agar. There was strong evidence that cloves possessed the greatest antagonistic effect on the growth of E. coli O157:H7 colonies. When cloves (at a 1.0% concentration) were combined with ground beef and incubated, growth was inhibited and the mean colony forming units per milliliter (CFUs/ml) was 5.10 x 10¹² compared to 4.32 x 10¹⁸ CFUs/ml when ground beef was not treated with cloves. A statistically significant reduction in the numbers of CFUs/ml after treatment of ground beef with cloves was detected. The results have the potential to have many implications on the way ground beef may be packaged in the future.

Research Advisor: Beverly J. Brown, Ph.D., Nazareth College