Browsing by Author "Sophia Kathariou, Committee Member"

Now showing 1 - 5 of 5

Antimicrobial Susceptibility Profiles and Clonal Population of Multidrug Resistant Campylobacter coli Isolates from Commercially Grown Turkeys.
(2011-02-04) Ahmad, Harun; Sophia Kathariou, Committee Chair; Jonathan Allen, Committee Member; Donna Carver, Committee Member; Deborah Threadgill, Committee Member; Sophia Kathariou, Committee Member
Behavior of Listeria monocytogenes Biofilms in a Simulated Food Processing (SFP) Ecosystem
(2006-08-25) Pan, Youwen; Fred Breidt, Committee Chair; Sophia Kathariou, Committee Member; Hosni Hassan, Committee Member
The purpose of the research has been to develop an experimental biofilm ecocystem for the characterization of Listeria monocytogenes biofilms in a simulated food processing (SFP) environment. Individual strains of L. monocytogenes were initially surveyed for their ability to attach to surfaces and form biofilms under a variety of conditions. Five strains of L. monocytogenes were then screened for optimal cell attachment and biofilm formation. Significant differences in surface attachment and biofilm formation were observed among the different strains of L. monocytogenes. The biofilms of the five-strain mixture of L. monocytogenes were formed on surfaces that are commonly used in food processing facilities, such as stainless steel and Teflon®. The biofilms were subjected to the SFP system in sequential 24-h daily cycles. Conditions of the SFP system included: starvation, washing, rinsing, and sanitation that routinely occur in a food processing plant. Cell survival in biofilms was determined during the time course of the experiment. The susceptibility of the cells in biofilms and detached cells to different sanitizers was measured. The morphology of the cells in biofilms and the planktonic cells detached from biofilms was observed. The study indicated that the progressive resistance developed by L. monocytogenes biofilms to a sanitizer could protect the cells in biofilms from this and other sanitizing agents. The progressive resistance and cross protection was observed in biofilms, but not in detached cells. These findings could provide a basis for further research on the mechanism of progressive resistance to stresses by L. monocytogenes in biofilms under food processing conditions. The data may help to establish effective sanitation programs for food processing and related industries.
Effects of Carcass Washing Systems on Campylobacter Contamination in Large Broiler Processing Plants
(2003-06-19) Bashor, Michael Paul; Kevin Keener, Committee Co-Chair; Pat Curtis, Committee Co-Chair; Brian Sheldon, Committee Member; Sophia Kathariou, Committee Member
Campylobacter, a major food borne pathogen found in poultry products, remains a serious problem facing poultry processors. Campylobacter research has primarily focused on detection methods, prevalence and detection on carcasses, with limited research conducted on intervention. The aim of this study was to assess the effectiveness of carcass washing systems in four large broiler-processing plants in removing Campylobacter species. Washing systems evaluated included combinations of inside/outside carcass washers and homemade cabinet washers. Processing aids evaluated were trisodium phosphate (TSP) and acidified sodium chlorite (ASC). The washer systems consisted of 1 to 3 carcass washers and used from 0.57 to 2.57 gallons of water per carcass. The washer systems used chlorinated water with 25 to 35 ppm of total chlorine. These washer systems on average reduced Campylobacter populations log 0.5 cfu/ml from log 4.8 cfu/ml to log 4.3 cfu/ml. Washer systems with TSP or ASC reduced Campylobacter populations on average by an additional log 1.03 to log 1.26 respectively. Total average reductions in Campylobacter populations across the washer system and chill tank were log 0.76 cfu/ml. Washer systems that included antimicrobial systems had total average reductions in Campylobacter populations of log 1.53 cfu/ml. These results suggest that carcass washer systems consisting of multiple washers provide minimal reductions in Campylobacter populations found on poultry in processing plants. A more effective treatment for reducing Campylobacter populations is ASC or TSP treatments; however, these reductions, while significant, will not eliminate the organism from raw poultry.
In-Package Heat Pasteurization Combined with Biocide-Impregnated Packaging Films for Inhibition of Escherichia coli 0157:H7 and Campylobacter jejuni.
(2003-11-05) Hughes-Hollar, LaVonda Ann; Patricia A. Curtis, Committee Co-Chair; Sophia Kathariou, Committee Member; Geraldine Luginbuhl, Committee Member; Paul L. Dawson, Committee Member; Brian W. Sheldon, Committee Co-Chair
Even with HACCP food safety programs in place, millions of pounds of ready-to-eat food products are recalled annually due to product recontamination after cooking and prior to packaging. As a consequence of this risk of contamination, numerous cases of foodborne illness occur yearly. Food processors are extremely interested in identifying and implementing additional food safety critical control points during and following packaging operations that would ensure that consumers receive products that are of high quality and that are safe. The first objective of this study was to generate and evaluate the thermal inactivation and lethality kinetics of E. coli O157:H7 and C. jejuni inoculated on the surface of vacuumpackaged, low-fat turkey bologna slices. This investigation included determining decimal reduction times (D-values) and ZD-values, activation energies, and rates of inactivation for these two pathogens. Packaged samples were submerged in a pre-heated water bath at temperatures of 55°, 60°, 65°, 70°, and 75°C or 53°, 55°, 60° and 62°C for E. coli O157:H7 and C. jejuni, respectively. The corresponding D-values calculated from survivor plots for E. coli O157:H7 were 289.5, 45.8, 15.8, 11.9 and 9.1 seconds, respectively (zD-value = 13.9°C). D-values for C. jejuni at 53°, 55°, 60°, and 62°C were 272.0, 192.1, 38.4, and 25.2 seconds, respectively (zD-value = 8.3°C). These findings indicate that C. jejuni has greater temperature dependence (i.e., more heat sensitive) than E. coli O157:H7. The second objective of this study was to examine the inhibitory activity of a wheat gluten (70% w/w) and glycerol (30% w/w)-based film containing 500 μg/ml nisin as Nisaplin, 3% citric acid, 5 mM EDTA, and 0.50% Tween 80 (Film+N) against E. coli O157:H7 and C. jejuni suspended in 0.1% peptone water. Alternatively, a control wheat gluten and glycerol-based film (Film) lacking nisin and the other treatment components and a 0.1% peptone water suspension without any films (Control) were tested. While the E. coli O157:H7 population increased 3-logs over the 72 hour exposure period (~23°C) for the Control and Film treatments, the Film+N treatment population decreased by 2-logs (a 5.6 to 7.4 log reduction). In contrast, C. jejuni populations decreased to below the minimum detectable level (log 1.2 cfu/ml) after 24h exposure to all three treatments. However, C. jejuni populations exposed to the Film+N treatment died at approximately twice the rate as the other two treatments. Information gleamed from the previous two studies was used in designing a third study where inoculated bologna samples were subjected to a minimal in-package pasteurization process (≤1-log reduction) combined with the inhibitory films. A heat treatment of 60°C for 60 seconds was initially applied to the inoculated and vacuumpackaged bologna and film treatments and then stored at 4°C for 7 days. A duplicate study involving only E. coli O157:H7 was also conducted but the storage time was extended to 5 weeks. Minimal reductions in E. coli O157:H7 populations of 1.0, 0.5, and 0.35 log cfu/ml were detected across the Control, Film and Film+N treatments, respectively, following the seven day storage/exposure period. Following the extended five week refrigerated storage period, the E. coli O157:H7 populations declined by 1.74, 1.14 and 0.27 log cfu/ml, respectively. For C. jejuni, population reductions of log 1.51, 2.11, 2.68 cfu/ml were detected for the Control, Film and Film+N, respectively, following the 7-day refrigerated storage period. The findings of this study demonstrate that wheat gluten and glycerol packaging films containing nisin, chelators and a surfactant are more inhibitory against bacterial pathogens when suspended in a liquid system as opposed to contact with a relatively dry ready-to-eat food (bologna). The loss of inhibitory activity in the combined in-package pasteurization and film treatment may be related to a lack of product moisture necessary to facilitate extraction and migration of the treatment components to the food surface. The ultimate goal of this line of investigation is to develop a modified inhibitory packaging film that would prove useful as one of several food safety .hurdles. that collectively might contribute to producing safer and higher quality food products having extended shelf lives.
Prevalence and Persistence of Select Foodborne Pathogens in a mid-Atlantic Turkey Processing Facility
(2005-05-31) Stam, Christina Nicole; Sophia Kathariou, Committee Member; Brian Sheldon, Committee Member; Lee-Ann Jaykus, Committee Chair
Listeria monocytogenes, Salmonella and Campylobacter combined are responsible for the majority of foodborne disease hospitalizations and over 1200 deaths annually in the U.S. alone. Although raw poultry has been identified as a source of these pathogens, most microbiological studies have focused on broilers with little attention given to turkey processing. The purpose of this research was to investigate the prevalence of select pathogens (L. monocytogenes, Salmonella spp., and Campylobacter spp.) and microbiological indicators (Enterococcus spp.) in the turkey processing environment. Environmental samples were collected in one Southeastern processing facility using swab methods at two month intervals over a period of 14 months. Samples were taken from conveyors, drains, walls and various food contact surfaces. Isolation and identification of bacteria was done using the USDA-FSIS Microbiology Laboratory Guidebook protocols. The prevalence of contamination was 11.5%, 7.4%, and 0.4% for L. monocytogenes, Salmonella, and Campylobacter, respectively. Enterococcus spp., an environmental indicator of fecal contamination, were isolated from over >75% of the samples screened. Salmonella isolates were typed using pulsed-field gel electrophoresis (PFGE) and Enterococcus isolates were speciated by PCR with antibiotic resistance profiles characterized using the SensiTitre system. A diverse set of relatively non-persistent Salmonella strains were obtained from the processing environment, as evaluated by PFGE. Thirty-nine percent of the Enterococcus isolates were speciated as E. faecium and 55% were E. faecalis. Both E. faecalis as E. faecium strains were susceptible to most antibiotics of human clinical relevance. Thirty-three L. monocytogenes strains were screened for their biofilm formation capabilities using a microtiter well assay. None of the strains formed a biofilm in monoculture; however, sixteen of the strains were able to form a biofilm in the presence of another organism. Data collected in prevalence studies such as this one can help processors identify contamination frequency and sites in an effort to control resident pathogenic bacteria in the processing environment.