Listeria monocytogenes is the etiological agent of a life-threatening, opportunistic infection caused by the ingestion of contaminated foods. Although L. monocytogenes is divided into 13 serotypes, 98% of human illness is caused by serotype 1/2a, 1/2b and 4b strains, with serotype 4b accounting for almost all the major outbreaks of human listeriosis. The principle objective of this work was to develop surface-binding monoclonal antibodies (MAbs) highly specific for serotype 4b, as well as characterize their antigen targets to aid in the detection and isolation of serotype 4b strains using an antibody based procedure. To create such antibodies, mice were immunized with formalin killed whole cells of L. monocytogenes serotype 4b strain LI0521. A total of 15 MAbs reactive to serotype 4b isolates were shown to recognize a ~77 kDa surface antigen subsequently identified by mass spectrometry as surface associated autolysin, IspC. Epitope mapping experiments further revealed that each of the 15 MAbs bound to the cell wall binding GW domain of IspC and can be essentially divided into 4 major groups based on epitope localization. ELISA analysis of the reactivity of each of the MAbs with various L. monocytogenes serotypes indicated that several MAbs were 100% specific for serotype 4b isolates. Surface plasmon resonance experiments showed that the affinity constants for each of these MAbs fell within the range of 1.0 x 10-7 to 6.4 x 10-9 M. To determine whether IspC, shown to be well conserved among various serotype 4b strains, is a useful diagnostic marker with antibody-based methods, the expression of IspC was assessed in L. monocytogenes cultured under normal and stress conditions. A functional promoter directing the transcription of ispC gene was identified immediately upstream of the ispC open reading frame by constructing the promoterless lacZ gene fusion with the putative ispC promoter region and by 5'RACE analysis. Data obtained with the lacZ reporter gene system and immunofluorescent microscopy revealed that IspC is expressed on the cell surface under all growth conditions tested (temperature, osmotic stress, pH, ethanol, oxidative stress, anaerobic conditions, carbon source and enrichment media) that allow for cellular division, although the level of ispC gene expression varies. In addition, a significant effort were put into elucidating the hydrolytic bond specificity of IspC by HPLC and mass spectrometry analysis of muropeptides released from IspC-mediated hydrolysis of L. monocytogenes peptidoglycan (PG). The results demonstrated that IspC functions as an N-acetylglucosaminidase capable of cleaving the β-1,4-glycosidic bond of the PG glycan strand. Furthermore, IspC was more efficient at hydrolysing fully Nacetylated PG from a PG deacetylase gene (pgdA) deletion mutant of L. monocytogenes than partially de-N-acetylated wild-type PG, indicating that modification of PG by de-Nacetylation of GlcNAc residues renders PG resistant to IspC hydrolysis. In conclusion, the surface autolysin IspC with the N-acetylglucosaminidase activity is a novel diagnostic marker for the 4b serotype strains, which can be explored , in conjunction with specific MAbs developed here, for detection and isolation of L. monocytogenes serotype 4b strains directly from food, environmental and clinical samples with the need for minimal or no culture enrichment.

The objective of this dissertation was to (1) determine which grow-out and processing sampling points best predicts and causes Campylobacter later in production (2) identify risk factors within the hatchery that influenced Campylobacter prevalence later in production (3) identify biosecurity risk factors that were associated with Campylobacter presence during production and processing (4) identify farm and production characteristics that were associated with Campylobacter presence later in production, and (5) to estimate the proportion of variance and the intraclass correlation coefficients within the hierarchical levels (complex, farm, bird) of the data. The best predictors of post-chill Campylobacter carcass status were the exterior whole carcass sample in the grow-out environment and the crop upon arrival at the processing plant. The best post-chill causal model contained the grow-out whole carcass. Variables associated with the increased odds of a Campylobacter positive sample included controlling the humidity in the hatchery chick room, 2-4 people handling the chicks at the hatchery, washing the setter twice yearly, 2 or more breeder farms providing eggs for the sampled flock, using low water pressure when washing the hatch trays, having more walk-in doors on the boiler house, the farmer removing the litter from the farm, concrete at most used door of the broiler house, the number of workers that work with the birds during grow-out, having more houses on the farm, standing water on the farm day 1, wood interior walls, a vegetation surface next the house footing, and 6 or less flocks on the litter. Protective factors included the use of footbaths and dedicated shoes, greater frequency of entering the house during brooding, disinfectant added to the drinker lines, having concrete outside the most used door, the cleanliness of the workroom, and harvesting birds at 56-63 days of age. The highest percent of variance occurred at the farm level meaning intervention efforts should focus on factors at the broiler farm level i.e. factors that are different among farms within a broiler complex.

Child care providers in Mississippi are required by the Mississippi Health Department to obtain food manager’s training and certification. The TummySafe© program satisfies this requirement and is offered in a self-paced computer delivered version and a traditional classroom version. This research explores participant changes in attitude and self-reported behaviors in the two methods of curriculum delivery as well as the correlation of knowledge change with attitude and self-reported behavior change. A quasi-experimental, pre-test/post-test design was used. Attitude change was not significantly different in the two methods. Traditional participants reported a higher change in self-reported behaviors than computer delivered participants. Both attitude and self-reported behavior change were positively correlated with knowledge gain.

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Understanding ways of improving the safety of food is an important area of research. In this project, I explore the history of the food safety systems in the United States and the Republic of Zambia. Focusing on the traceability of meat (as a form of risk management), I reveal the factors shaping each of these systems, with an eye towards their similarities and differences. I argue that food safety systems come to look different due to how these regulatory systems differently define risk, some of which traceability has brought to light. In both countries, what influences risk cultures is trust in institutions, political leaders and in science and technology. For the Zambian public, trust is in local political leaders, in individuals and in brands. For the US public, trust is in information and knowledge of producers, which is found on labels. While the Zambian public generally trusts institutions, the US public, due to its history of institutional failures, does not. / Master of Science / Tracing where food comes from can be an important aspect of our food system. In this project, I show why food safety systems in the United States and Zambia look the way they that they do today. I do this by specifically focusing on how the two nations trace beef throughout the food supply chain. I show the different factors that have led to the food systems to look the way they do. My argument is that in the US and Zambia, there are non-scientific reasons why these food systems to look the way that they do today and why these countries address risk differently.

Romaine lettuce and leafy greens have been at the center of food safety concerns over the last several years. More specifically, romaine lettuce has been directly linked to seven(7) foodborne illness outbreaks and resulted in five(5) recalls over the eight(8) years period of January 1, 2012, to December 31, 2019. This paper estimates the effects that these food safety events have had on the price returns of romaine lettuce utilizing a series of Generalized Autoregressive Conditional Heteroskedasticity (GARCH) models. Importantly, the GARCH models allowed us to capture the effects of the recall and illness outbreaks on both the returns and volatility of the romaine price series. We find that three (3) of the seven (7) illness outbreaks resulted in marked increases in the price returns - between 4.1% and 9.6%. Conversely, three (3) of the five (5) recalls reduced price returns - between 30% and 57%. However, the volatility is not found to be significantly nor to affect the price volatility significantly. We conclude that recalls serve as a market correction in the romaine lettuce market. Consequently, a continued focus on increasing traceability with in the romaine lettuce market will help to reduce price fluctuation and limit the number of illnesses resulting from outbreaks. / Master of Science / Romaine lettuce and leafy greens have been at the center of food safety concerns over the last several years. More specifically, romaine lettuce has been directly linked to 7 foodborne illness outbreaks and resulted in 5 recalls over the eight years, January 1, 2012, to December 31, 2019. This paper estimates the effects that these food safety events have had on the price returns of romaine lettuce. It was found that 3 of the seven illness outbreaks resulted in marked increases in the price returns - between 4.1% and 9.6% while, 3 of the 5 recalls reduced price returns - between 30% and 57%. However, the volatility is not found to be significantly nor to affect the price volatility significantly. It is concluded that recalls serve as a market correction in the romaine lettuce market. A continued focus on increasing traceability with in the romaine lettuce market will help to reduce price fluctuation and limit the number of illnesses resulting from outbreaks.

The latest edition of the Food and Drug Administration's Model Food Code provides the definition of an acceptable donated food item but does not specify any safe storage or handling standards for these items. Virginia has not adopted this edition, but its own food handling regulations provide liability protections to food donors and exempt food pantries from any relevant retail food handling regulations. This means that food pantries must provide their own oversight over implementation of safe food handling requirements. Some pantries only accept nonperishables, but others accept both perishable and nonperishable food, or prepare/repurpose food on site. Therefore, pantries have varying needs in terms of safe food handling and preparation oversight and guidance. This project aims to observe food safety practices at food pantries within Virginia, and to establish a set of recommendations based on these observations for food pantries to consider implementing. Twenty pantries throughout the Commonwealth of Virginia were observed when distributing food using a standardized rubric. This rubric allowed the observer to collect detail on food storage, handling, and preparation at the pantry. Each pantry was visited once and observed for about two hours. The manager of the pantry completed a survey to determine basic food safety knowledge. Generally, pantries successfully followed basic food safety guidelines, however there were some clear risky practices observed. These included improper handwashing, improper storage of perishable items, and improper volunteer personal hygiene. There were only two handwashing attempts observed between all 20 pantries and neither of these attempts was correct. In addition, 8 of 20 (40%) of the pantries did not keep up to date records of their refrigerator and freezer temperatures. Lack of personal hygiene, especially the use of personal items while handling food and lack of glove usage, was a concern. 9 of 20 (45%) of pantries had someone on site using a personal item while handling food, and 4 of 6 (67%) of pantries that prepared or cooked food on site had volunteers improperly wearing gloves during these activities. Managers at seventeen of twenty (85%) pantries reported completing some type of food safety training while only volunteers at six of twenty (30%) pantries reported the same. This demonstrates gaps in knowledge between volunteers and managers. The results of this study demonstrate the need for standard operating procedures (SOPs) to be made available for food pantries, as well as a food safety training created specifically for food pantry volunteers that is applicable to their scope of work. / Master of Science in Life Sciences / The latest edition of the Food and Drug Administration's Model Food Code provides the definition of an acceptable donated food item but does not specify any safe storage or handling standards for these items. Virginia has not adopted this edition, but its own food handling regulations provide liability to food donors and exempt food pantries from any relevant retail food handling regulations. This means that food pantries must provide their own oversight over implementation of safe food handling requirements. Some pantries only accept nonperishable food items, but others accept both perishable and nonperishable food, or prepare/repurpose food on site. Therefore, pantries have varying needs in terms of safe food handling and preparation oversight and guidance. This project aims to observe food safety practices at food pantries within Virginia, and to establish a set of recommendations based on these observations for food pantries to consider. Twenty pantries throughout the state of Virginia were observed during distribution using a standardized rubric. This rubric allowed the observer to collect detail on food storage, handling, and preparation at the pantry. Each pantry was visited once and observed for two hours. The manager of the pantry completed a survey on general basic food safety knowledge. Generally, pantries successfully followed basic food safety guidelines, however there were some clear risky practices observed. Consistently, these included risky practices around handwashing, proper storage of perishable items, and personal hygiene of volunteers. The results of this study show a pointed need for standard operating procedures (SOPs) to be created for food pantries, as well as a food safety training created specifically for food pantry volunteers that is applicable to their scope of work.

Thesis advisor: Babak Momeni / Thesis advisor: Charles Hoffman / Aflatoxins (AFs) are secondary fungal metabolites that contaminate common food crops and are harmful to humans and animals. The ability to remove AFs from feed commodities will improve health standards and counter the economic drain inflicted by AF contamination. Strategies to mitigate AF contamination fall into three categories: physical, chemical, and biological. In this thesis, I explore the identification of degraders and degradation mechanisms, as well as their enhancement, within the context of chemical and biological strategies. Known chemical strategies have used strong acids and bases to remove contaminating AF, but these methods often lead to ecological waste issues downstream. Chapter 3 investigates the application of weaker acidic and alkaline conditions to remove two types of AFs, AFB1 and AFG2. I find that a weakly alkaline environment is sufficient to degrade AF, providing an alternative solution for chemical decontamination. Biodetoxification is a promising solution to AF contamination because of its low cost and few undesired environmental side-effects. Microbes possess a rich potential for removing toxins and pollutants from the environment. Despite the fairly wide availability of this potential, identifying suitable candidates and improving them remain challenging. In Chapter 2, I explore the use of computational tools to discover strains and enzymes that detoxify harmful toxins. Of focus is the detoxification of mycotoxins by biological enzymes. Existing computational tools can be used to address questions in the discovery of new detoxification potential, the investigation the cellular processes that contribute to detoxification, and the improvement of detoxification potential in discovered enzymes. I showcase open bioremediation questions where computational researchers can contribute and highlight relevant existing and emerging computational tools that could benefit bioremediation researchers. In Chapter 4, I screen several environmental isolates for their AF detoxification ability, using AFG2. I used different carbon sources (glucose and starch) as isolation and culturing media to examine the effect of the environment on degradation ability. Overall, I find that starch medium expedites the screening process and generally improves the performance of isolates, making this a promising method for identifying new degraders and enhancing their performance. Chapter 5 highlights the characterization of degradation by two promising Rhodococcus species, R. erythropolis and R. pyridinivorans. While previous work has identified their degradation ability, further investigation into degradation mechanisms has been understudied. Here, I explore the characterization of degradation mechanisms toward enzyme identification. Finally, the appendix starts to broach the question of enhancing degradation of known degrading enzymes, the example here is laccase from the fungus Trametes versicolor. Using molecular dynamic and quantum mechanics simulations to identify mutations of interest in increasing the affinity of laccase toward AF, I create five mutants to test their degradation against the performance of wildtype. These mutants show a range of improvements against AF and showcase the efficacy of this approach to enhancement. Together, this body of work highlights the importance of understanding AF degradation for the creation of new strategies of AF mitigation. My thesis provides a framework for developing AF decontamination strategies, from identifying degraders and unlocking their mechanisms to enhancing their performance. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Master of Science / Department of Agricultural Economics / John A. Fox / The United States has been inspecting commercial meat processing for over 100 years. Currently there is a push to increase the number of bacteria that meat processors are responsible to test for, which would lead to an increase in the costs of production. The goal of this thesis was to investigate antimicrobial practices used in small beef processing facilities across the Great Plains and the costs associated with those practices. A survey instrument was constructed and administered resulting in a total of 39 usable surveys for analysis. Preliminary analysis of the data was followed by an ordinary least squares regression to determine cost increasing or decreasing practices and attributes of the small processors. It was determined that on average small meat processors face a per ton variable cost of $914.71 or $0.46 per pound. Regression analysis indicated that plants can benefit from economies of scale. It was also determined there are no cost savings from being a state inspected as opposed to a federally inspected plant. Certain practices such as dry aging beef to increase quality and decrease bacterial load were found to increase the variable cost per pound. Microbial testing accounted for only 0.5% of the total variable cost of production.