Influence of Eukaryotic Microflora on the Survival of Escherichia coli O157:H7 in Compost Slurry

Open Access
- Author:
- Puri, Amrita
- Graduate Program:
- Food Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 11, 2009
- Committee Members:
- Edward G Dudley, Thesis Advisor/Co-Advisor
Edward G Dudley, Thesis Advisor/Co-Advisor - Keywords:
- compost
E. coli O157:H7
survival - Abstract:
- An increasing number of food-borne illnesses are associated with the consumption of fresh produce, leading to a growing interest in the development of strategies to minimize preharvest contamination. Compost made from livestock manure is commonly used as a crop fertilizer and serves as a possible route of transmission for Escherichia coli O157:H7 spread to fresh produce. Therefore, a better understanding of factors contributing to the survival of E. coli O157:H7 in compost material is essential to ensure produce safety. In this study, we hypothesized that the indigenous microflora present in composts adversely affects the survival of E. coli O157:H7. E. coli O157:H7 exhibited a ~4 log reduction in survival over a period of 16 days. At 37˚C, the pathogen was undetectable by day 15. When compost was supplemented with the eukaryotic inhibitor cycloheximide, E. coli O157:H7 exhibited a significant improvement in survival. Analysis of microbial communities present in the compost with denaturing gradient gel electrophoresis (DGGE) suggested minor differences in the fungal communities present in cycloheximide treated compost compared to untreated compost over a period of 8 days. However, DGGE profiles of protists showed significant differences in community complexity. In addition we found that in the absence of moisture, there was no significant difference in survival of E. coli O157:H7 in the cycloheximide-amended compost. It is speculated that protists excyst in moisture-rich compost and feed on E. coli O157:H7. This leads us to conclude that predation of E. coli O157:H7 by protists might be a potential mechanism of killing E. coli O157:H7 in compost materials.