The Influence of Environmental Microbiota in the Control of L. monocytogenes
Open Access
- Author:
- Sinclair, Priscilla
- Graduate Program:
- Food Science
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- May 17, 2021
- Committee Members:
- Robert Roberts, Program Head/Chair
Jasna Kovac, Thesis Advisor/Co-Advisor
Darrell William Cockburn, Committee Member
Luke F Laborde, Thesis Advisor/Co-Advisor - Keywords:
- L. monocytogenes
Microbiota - Abstract:
- Foodborne pathogens cause an estimated 128,000 hospitalizations and 3,000 deaths in the United States of America each year. L. monocytogenes is one of the leading causes of foodborne illness related deaths in the USA. Many L. monocytogenes outbreaks originate from food packing and/or processing environment (FDA, 2015, 2020, 2021; Pouillot et al., 2016), demonstrating a need for enhanced cleaning and sanitizing procedures. In part, L. monocytogenes is able to survive in the environment by biofilm formation as well as beneficial relationships with other microorganisms. Biofilms are difficult to remove once established and shield the microorganisms within them from lethal levels of sanitizers. Multiple studies have characterized the microbiome of various food packing and processing environments; however, it is unknown if the microbial families identified are universally found in food processing environments or unique to those included in the studies. In this thesis we aim to improve the understanding of the distribution of bacterial families found in food processing environment by determining the core microbiota of animal- and plant- based food processing facilities as well as the taxa that are differentially abundant among them. We also aim to assess the efficacy of two biocontrol lactic acid bacteria (LAB) strains against L. monocytogenes in a quasi-biofilm assay. In order to assess the first aim, literature review was conducted to identify papers that characterized the microbiota in food processing or packing environments using Illumina 16s amplicon sequencing. The published data from the identified papers were then analyzed using Mothur v 1.44.2 and underwent downstream analysis to determine the core microbiota in animal- vs plant-based environments as well as the differentially abundant taxa between the two environments. In order to assess the efficacy of two LAB biocontrol strains to inhibit L. monocytogenes they were first tested against phylogenetically distinct L. monocytogenes isolates in a spot inoculation assay. The strains were then grown with L. monocytogenes in apple packinghouse microbiome samples for 3-,5-, and 15-days in order to assay their ability to inhibit L. monocytogenes in an attached biomass. The microbiota at experimental end point was characterized for all quasi-biofilms. The secondary analysis included eight previously published studies that sampled food processing environments. The Families Moraxellaceae and Flavobacteriaceae were identified as the shared core microbiota between animal- and plant- based common core microbiota. The biocontrol LAB strains were able to inhibit all distinct L. monocytogenes isolates in a spot inoculation assay. However, the two biocontrol strains were unable to reduce L. monocytogenes in 3- and 5-day quasi-biofilms. The biocontrol strains were able to reduce L. monocytogenes in the 15-day quasi biofilms, however, all reductions were below 0.50 log MPN/mL. These studies will help to inform development of enhanced cleaning and sanitizing procedures for control of L. monocytogenes.