Food Microbiology Commons^™

Influence Of Lipoteichoic Acid On Listeria Monocytogenes Biofilm Formation And Cellular Stress, Imelda T. Brooks

Doctoral Dissertations

Lipoteichoic acid (LTA) is an important polymer on the surface of Gram-positive organisms, including the foodborne, biofilm-forming pathogen Listeria monocytogenes, and is connected to the cell membrane through a glycolipid backbone. Previous results have shown the importance of LTA in cell viability and biofilm formation. The purpose of this research is to further investigate the influence of LTA in L. monocytogenes biofilm formation and how the bacterium responds to environmental stress caused by antimicrobial exposures, and a combination of low temperature and high osmolarity. We created in frame deletion mutants along the operon lmo-2555-lmo2554-lmo2553, which have been shown …

Susceptibility Of Escherichia Coli O157:H7, Salmonella Enterica Sp., And Listeria Monocytogenes To Antimicrobial Mixed Micelle Delivery Systems, Chanelle N. Adams

Doctoral Dissertations

Within the food industry, there is an ever increasing demand to improve the quality of food and ensure safety from pathogenic/spoilage microorganisms. Globalization of the food industry in the 1990’s, in conjunction with the worldwide shipment of food created a need for the extension of shelf-life and enhanced maintenance of food quality (12). In the United States alone, the Centers for Disease Control and Prevention report that each year, roughly 1 in 6 Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases; this correlates to approximately $77.7 billion in economic loss annually (17). …

Nisin Resistance Of Bacillus Cerus: Preparation Of Nisin, Peter Weber

Journal of Undergraduate Research at Minnesota State University, Mankato

Nisin is a peptide that is made by the bacterium Lactococcus lactis. Nisin is a small molecule that kills gram positive bacteria by binding to their membrane and by disrupting the proton motive force. When food is processed it is heated to kill bacteria, but some bacteria still survive. Adding nisin to the food provides a second barrier for the growth of the bacteria. Purified nisin has become quite expensive in the current marketplace. Therefore this study is directed at producing nisin and purifying it. L. lactis was grown in five different media (BHI, BHI + 1% glucose, BHI + …

Characterization Of Commercial Probiotics: Antibiotic Resistance, Acid And Bile Resistance, And Prebiotic Utilization, Carmen Lucia Cano Roca

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Probiotics, live microorganisms that beneficially affect the health of their host, must undergo extensive research to ensure they are safe for consumption and possess certain functional properties. Antibiotic resistance in probiotics has raised concern due to the possibility of its transfer to pathogens. Acid and bile tolerance ensures that organisms will survive passage into the intestines. Prebiotic utilization indicates ability to ferment specific carbohydrates for enhanced growth. The objective of this study was to characterize a group of commercial probiotics for their suitability as probiotics.

Nine commercial probiotic strains (7 Lactobacillus, 1 Lactococcus lactis, and 1 Bifidobacterium longum …

Transfer And Survival Of Microorganisms To Produce From Surface Irrigation Water, Stuart Jamison Gorman

Masters Theses

Surface water irrigation sources are widely used for fruit and vegetable crop production in the United States. Surface water is inherently prone to direct and indirect contamination with animal fecal material. Hence, the microbial quality of surface water sources can be highly variable. Water used for irrigation is considered a common source for produce contamination. In addition to this, fruits and vegetables are commonly consumed fresh or minimally processed, thus emphasizing the need for preventative measures in production of fresh produce. This study will examine transfer from naturally contaminated irrigation water to cantaloupes using drip and overhead spray irrigation methods. …

Probiotic Potential Of Bacterial Isolates From ‘Amabere Amaruranu’ Cultured Milk, Blaise B. Boyiri

Electronic Theses and Dissertations

Probiotics are viable nonpathogenic microbes that positively affect host health. Probiotics inhibit infection, activate immunity, and promote mucosal-barrier development. Many microbes have probiotic activity. Nonetheless, the selection of stable strains and their specific mechanism(s) of action are not fully elucidated. Bacteria from ‘Amabere amaruranu’ cultured milk from Kenya were isolated and identified by PCR sequence analysis of the 16S rRNA gene. Isolates were examined for stability to acid and bile, antimicrobial activity, mucin production, and degradation and sensitivity to antibiotics, hence their potential for probiotics. Lactobacillus isolates were acid unstable, bile-stable, nonmucinolytic, and presented antibacterial activity. L. rhamnosus cell fractions …

Adherence Inhibition Of Human Pathogens Campylobacter Jejuni And Campylobacter Coli By Non-Digestible Oligosaccharides, Alejandra Ramirez-Hernandez

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Adherence is the first and one of the most important steps of bacterial pathogenesis. Natural derived components that inhibit the adherence of pathogens to the surface of epithelial cells have received considered interest. The goal of this research was to assess the anti-adherence activity of mannan oligosaccharides (MOS), pectic oligosaccharides (POS) and cranberry high molecular weight component (HMW) against Campylobacter jejuni and Campylobacter coli. First the anti-adherence activity of MOS and their purified fraction (pMOS) was tested against three strains of C. jejuni and two strains of C. coli. Results shown significant reductions in adherence (up to 70%) …

Non-Digestible Oligosaccharides: Anti-Adherence And Other Biological Properties, Maria I. Quintero-Villegas

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Bacterial adherence is the first and one of the most important steps in bacterial pathogenesis. Adherence to host cell surfaces requires that the bacteria recognize specific receptors in the surface of epithelial cells. Therefore, agents that act as molecular decoys to interfere with adherence could be useful prophylactic treatments to prevent or mitigate the onset of infections. The goal of this research was to assess the ability of several food grade non-digestible oligosaccharides (NDOs) to act as molecular decoys and prevent bacterial adherence in vitro as well as in vivo. First, the antiadherence effect of specific species chitooligosaccharides (CHOS) …

Understanding The Factors Affecting Microbiological Quality Of Wheat Milled Products: From Wheat Fields To Milling Operations, Luis E. Sabillón Galeas

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Although regarded as a low-risk commodity, wheat flour-based mixes have been implicated in several food safety incidents. The present thesis is a compilation of five scientific manuscripts on the effect of weather variation, milling steps and implementation of pre-milling interventions on the microbiological quality and safety of wheat and milled products. The first manuscript is a review of the microbiological quality and safety of wheat-based products. Despite the low water activity, wheat flour may harbor dormant but viable microorganisms, which could lead to safety concerns when flour is used to produce refrigerated dough products. The second manuscript illustrates the effect …

Traceability Implementation In Organic Farming: Case Study, Chamomile Tea Production, Shaima Abdelfattah Ibrahim

Theses and Dissertations

Implementing a traceability plan in an herbal production plant is a complex task. In this study an attempt to integrate food safety, quality and traceability through the different stages of the organic German Chamomile (Matricaria recutita) production chain was made. First, all the current relevant international laws, regulations and standards regarding traceability, safety and quality, with emphasis on how and why they are necessary for any food production chain, were set forward. Second, physico-chemical and microbiological analyses were run throughout the different processing stages of production, for four different Chamomile batches produced over the same season using the same farming …

The Human/Animal Interface: Emergence And Resurgence Of Zoonotic Infectious Diseases, Michael Greger

Michael Greger, MD, FACLM

Emerging infectious diseases, most of which are considered zoonotic in origin, continue to exact a significant toll on society. The origins of major human infectious diseases are reviewed and the factors underlying disease emergence explored. Anthropogenic changes, largely in land use and agriculture, are implicated in the apparent increased frequency of emergence and reemergence of zoonoses in recent decades. Special emphasis is placed on the pathogen with likely the greatest zoonotic potential, influenzavirus A.

Amyloid Fibrils: Potential Food Safety Implications, Michael Greger

Michael Greger, MD, FACLM

The demonstration of oral Amyloid-A (AA) fibril transmissibility has raised food safety questions about the consumption of amyloidotic viscera. In a presumed prion-like mechanism, amyloid fibrils have been shown to trigger and accelerate the development of AA amyloidosis in rodent models. The finding of amyloid fibrils in edible avian and mammalian food animal tissues, combined with the inability of cooking temperatures to eliminate their amyloidogenic potential, has led to concerns that products such as pâté de foie gras may activate a reactive systemic amyloidosis in susceptible consumers. Given the ability of amyloid fibrils to cross-seed the formation of chemically heterologous …

Probiotics: Finding The Right Regulatory Balance, Diane E. Hoffmann, Claire M. Fraser-Liggett, Frank B. Palumbo, Jacques Ravel, Karen H. Rothenberg, Virginia Rowthorn

Karen H. Rothenberg

Some products marketed as drugs should be excused from Phase I trials, but safety and efficacy claims for dietary supplements should be more tightly regulated.

Probiotics: Finding The Right Regulatory Balance, Diane E. Hoffmann, Claire M. Fraser-Liggett, Frank B. Palumbo, Jacques Ravel, Karen H. Rothenberg, Virginia Rowthorn

Virginia Rowthorn

Some products marketed as drugs should be excused from Phase I trials, but safety and efficacy claims for dietary supplements should be more tightly regulated.

Thermal Inactivation Of Human Norovirus Surrogates And Hepatitis A Virus In Foods, Hayriye Bozkurt Cekmer

Doctoral Dissertations

Foodborne enteric viruses are the leading cause of gastroenteritis in humans. In particular, human noroviruses and hepatitis A virus (HAV) are the most important foodborne viral pathogens with regard to the number of outbreaks and people affected. Therefore, studies are needed to bridge existing data gaps and determine appropriate parameters for thermal inactivation methods for human norovirus and hepatitis A virus. Due to the absence of appropriate cell culture systems to propagate these viruses, cultivable surrogates (feline calicivirus, FCV-F9 and murine norovirus, MNV-1) are commonly used based on the assumption that they can mimic the viruses they represent. The objectives …

Investigating Antibiotic Resistance Levels Of Salmonella Internalized In Lettuce Leaves, Jason B. Thomas

McNair Scholars Research Journal

Contamination of food crops by the human pathogen Salmonella is a food safety threat worldwide. Though using treated wastewater for irrigation is a sustainable practice, it may introduce trace levels of Salmonella that may contaminate food crops. Salmonella could develop resistance to antibiotics present in wastewater. The overall goal of the project is to increase the understanding of the public health risk associated with the use of treated wastewater to irrigate food crops. The objective of this particular study is to determine the antibiotic resistance level of Salmonella internalized in lettuce leaves. In this experiment, thirty-six plants of the lettuce …

Inactivation Of Sporeforming Spoilage Bacteria In Milk And Juice Using Ultra High Pressure Homogenization, Julie Michelle Gidley

Masters Theses

Inactivation of spores is essential for extending the shelf life of fluid milk and other food products. Three studies were conducted to evaluate the effects of ultra-high pressure homogenization (UHPH) on spores from three spore forming bacteria. The first experiment studied UHPH effects on Geobacillus stearothermophilus, Paenibacillus lautus, and Bacillus licheniformis in fluid milk. Homogenization pressures of 100 - 500 MPa were applied to spore-inoculated samples, and spore viability was determined by plating onto agar media. Heat shock treatments (80°C, 10 min) were applied to a portion of each sample prior to UHPH. UHPH treatment significantly reduced spore populations on …

Chitosan Reduces Enteric Colonization Of Campylobacter In Young Chickens, But Not On Post-Harvest Chicken Skin Samples, Hanna Royce Arambel

Graduate Theses and Dissertations

Worldwide, Campylobacter is one of the leading causes of foodborne bacterial gastroenteritis causing an estimated 1.3 million infections in the United States alone. Consumption and/or cross-contamination of raw or undercooked poultry products have been linked as the most common source of Campylobacter infection, making the poultry industry a target for Campylobacter reduction strategies. Campylobacter is prevalent in most poultry flocks in the United States, with as many as 90% of flocks Campylobacter-positive at the time of slaughter. It is estimated that a reduction of Campylobacter in poultry would greatly reduce the risk of campylobacteriosis in humans. Unfortunately, there are …

Antimicrobial Activity Of Cinnamic Acid, Citric Acid, Cinnamaldehyde, And Levulinic Acid Against Foodborne Pathogens, Savannah G. Hawkins

Chancellor’s Honors Program Projects

No abstract provided.

Tracking Heat-Resistant, Sporeforming Bacteria In The Milk Chain: A Farm To Table Approach, Maricarmen Estrada Anzueto

Department of Food Science and Technology: Dissertations, Theses, and Student Research

Sporeforming bacteria (such as Bacillus and Paenibacillus spp.) can survive pasteurization conditions (Collins, 1981) and grow in pasteurized fluid milk during refrigerated storage (Huck et al., 2008; Ivy et al., 2012), causing fluid milk spoilage and limiting the further extension of fluid milk’s shelf life (Fromm and Boor, 2004; Durak et al., 2006). Moreover, Bacillus and related genera have been found in raw milk, pasteurized milk and environmental samples from dairy farms, indicating that these organisms are ubiquitous in nature and can enter the milk chain from different sources (Huck et al., 2007b; Huck et al., 2008; Ranieri and Boor, …