Publications by authors named "Mary L Tortorello"

Salmonella enterica is frequently implicated in foodborne disease outbreaks associated with fresh-cut fruits. In the U.S.

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Unpasteurized milk is used to produce aged artisanal cheeses, which presents a safety concern due to possible contamination with foodborne pathogens, especially . The objective of this study was to examine the composition of the bacterial community in unpasteurized milk used to prepare Gouda cheese artificially contaminated with (~1 log CFU/ml) and assess the community dynamics and their potential interaction with during a 90-day ripening period using targeted 16S rRNA sequencing. The diversity of bacterial taxa in three batches of unpasteurized milk was not significantly different, and the microbiomes were dominated by species of , , , and .

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Abstract: Environmental monitoring for Listeria monocytogenes in food processing environments is key for ensuring the safety of ready-to-eat foods. For sampling, swabs are often hydrated with a wetting or transport medium that may contain neutralizers and other ingredients. After swabbing the environment, the swabs may then be transported or shipped cold to an off-site laboratory for testing, ideally within 48 h.

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Abstract: Various methods exist for the enrichment and detection of Listeria spp. and Listeria monocytogenes from environmental samples. Procedures for the compositing of environmental samples are not as well defined.

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subspecies I (ssp 1) is the leading cause of hospitalizations and deaths due to known bacterial foodborne pathogens in the United States and is frequently implicated in foodborne disease outbreaks associated with spices and nuts. However, the underlying mechanisms of this association have not been fully elucidated. In this study, we evaluated the influence of storage temperature (4 or 25°C), relative humidity (20 or 60%), and food surface characteristics on the attachment and survival of five individual strains representing ssp 1 serovars Typhimurium, Montevideo, Braenderup, Mbandaka, and Enteritidis on raw in-shell black peppercorns, almonds, and hazelnuts.

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Refrigerated ready-to-eat (RTE) dips often have pH and water activity combinations conducive to the proliferation of foodborne pathogens, including Listeria monocytogenes. This study conducted product assessments of five refrigerated RTE dips: baba ghanoush, guacamole, hummus, pesto, and tahini, along with individual dip components including avocado, basil, chickpeas, cilantro, eggplant, garlic, and jalapeno pepper. Dips and dip components were inoculated with 2 log CFU/g of L.

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Abstract: Cheeses made with unpasteurized milk are a safety concern due to possible contamination with foodborne pathogens. Listeria monocytogenes and Escherichia coli O157:H7 have been implicated in several outbreaks and recalls linked to Gouda cheese made with unpasteurized milk. The U.

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Nuts and seeds have been increasingly associated with recalls due to contamination with Listeria monocytogenes. Storage of these food commodities occurs at various relative humidity (RH) conditions for months or years. The objective of this study was to assess L.

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Listeria monocytogenes was linked to an outbreak of foodborne illness associated with in-process contaminated ice cream in the United States from 2010 to 2015 that sickened 10 individuals and led to 3 deaths. Ice cream obtained from the outbreak was used in this study to examine the population dynamics of L. monocytogenes as in-process contaminants compared with artificially inoculated cells.

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Various outbreaks and recalls have been associated with contamination of ready-to-eat (RTE) food products, including dips. High pressure processing (HPP) is useful for reducing levels of bacteria in many RTE food products, but its efficacy for reduction of pathogens in RTE dips is not well understood. In this study, laboratory-prepared hummus, tahini, baba ghanoush, guacamole, and pesto were initially treated with HPP at 350 MPa for up to 240 s to assess inactivation and determine -values.

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Packaged fresh spinach has been associated with outbreaks of illness caused by O157:H7. The purpose of this study was to assess the behavior of O157:H7 in packaged baby spinach in response to storage conditions of temperature and package atmosphere and including effects of inoculation level, spinach leaf damage (cut leaves), internalized or leaf surface contamination, exposure to hypochlorite sanitizer, and package size. Behavior of O157:H7 inoculated at 2 and 4 log CFU/g on spinach packaged in polymer bags composed of a two-layer laminate (polypropylene and polyethylene) and stored under atmospheres of 20% O-3% CO and 0% O-15% CO (aerobic and anaerobic, respectively) was assessed at 5, 7, 12, and 15°C for up to 14 days.

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A multistate listeriosis outbreak associated with caramel apples from 2014 to 2015 prompted research on the survival of Listeria monocytogenes in fresh apples and caramel apples. Research indicated that stem end-inoculated caramel apples with stick insertion allowed for the survival and growth of L. monocytogenes at both refrigeration and ambient temperatures.

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This study assessed the growth of in milkshakes made using the process-contaminated ice cream associated with a listeriosis outbreak in comparison to milkshakes made with artificially contaminated ice cream. For all temperatures, growth kinetics including growth rates, lag phases, maximum populations, and population increases were determined for the naturally and artificially derived contaminants at 5, 10, 15, and 25°C storage for 144 h. The artificially inoculated presented lower growth rates and shorter lag phases than the naturally contaminated populations at all temperatures except for 5°C, where the reverse was observed.

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Cut produce continues to constitute a significant portion of the fresh fruit and vegetables sold directly to consumers. As such, the safety of these items during storage, handling, and display remains a concern. Cut tomatoes, cut leafy greens, and cut melons, which have been studied in relation to their ability to support pathogen growth, have been specifically identified as needing temperature control for safety.

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An outbreak of listeriosis in late 2014 and early 2015 associated with caramel apples led to questions about how this product became a vector for Listeria monocytogenes. This investigation aimed to determine information about the survival and growth of L. monocytogenes in both fresh apples and caramel apples, specifically examining the effects of site and level of inoculation, inoculum drying conditions, and storage temperature.

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Postharvest processes for fresh produce commonly include washing in water containing antimicrobial chemicals, such as chlorine; however, if the antimicrobials are not present in sufficient levels, washing can promote the spread of contamination that might be present. To understand cross-contamination risk during washing, we tested a collection of Shiga toxigenic Escherichia coli (STEC), including O157:H7 and other non-O157 strains, for certain traits during washing of fresh-cut lettuce, i.e.

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Recent epidemiological evidence indicates that preparation of fresh produce for use as ingredients in ready-to-eat food in commercial settings has been a significant source of the norovirus (NoV) infections in the U.S. This research investigated the dissemination of NoV from a single tomato to many others via the use of an 11-horizontal blade slicer commonly found in restaurants or sandwich shops.

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Multi-ingredient foods having low- or intermediate-moisture characteristics may pose a special challenge to process design and validation. Ingredients of these foods can create local microenvironments that may have a distinct impact on pathogen survival and processing requirements. In this study, two model systems, each consisting of 80% commercial peanut butter (P) and 20% nonfat dry milk powder (M), were formulated to be identical in composition, but different in the source of the Salmonella contamination as originating in either the ingredient P or M.

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Listeria monocytogenes is a foodborne bacterial pathogen and the causative agent of an infectious disease, listeriosis. L. monocytogenes is ubiquitous in nature and has the ability to persist in food processing environments for extended periods of time by forming biofilms and resisting industrial sanitization.

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Listeria monocytogenes is a food-borne bacterial pathogen and the causative agent of human and animal listeriosis. Among the three major genetic lineages of L. monocytogenes (i.

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Increased water activity in peanut butter significantly (P < 0.05) reduced the heat resistance of desiccation-stressed Salmonella enterica serotypes treated at 90 °C. The difference in thermal resistance was less notable when strains were treated at 126 °C.

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Salmonella enterica is a frequent contaminant of minimally-processed fresh produce linked to major foodborne disease outbreaks. The molecular mechanisms underlying the association of this enteric pathogen with fresh produce remain largely unexplored. In our recent study, we showed that the expression of a putative stress regulatory gene, ycfR, was significantly induced in S.

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The survival of Salmonella in low moisture foods and processing environments remains a great challenge for the food industry and public health. To explore the mechanisms of Salmonella desiccation resistance, we studied the transcriptomic responses in Salmonella Tennessee (Tennessee), using Salmonella Typhimurium LT2 (LT2), a strain weakly resistant to desiccation, as a reference strain. In response to 2 h of air-drying at 11% equilibrated relative humidity, approximately one-fourth of the open reading frames (ORFs) in the Tennessee genome and one-fifth in LT2 were differentially expressed (>2-fold).

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Significant differences (P < 0.05) were found between the survival rates of Salmonella enterica and Escherichia coli O157:H7 in peanut butter with different formulations and water activity. High carbohydrate content in peanut butter and low incubation temperature resulted in higher levels of bacterial survival during storage but lower levels of bacterial resistance to heat treatment.

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Fresh produce has been associated with multiple outbreaks of illness caused by Escherichia coli O157:H7. The mechanism of E. coli O157:H7 survival through postharvest processing of fresh produce needs to be understood to help develop more effective interventions.

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