The 16S/23S ribosomal RNA (rRNA) intergenic space (IGS) regions from pathogenic and non-pathogenic species (spp.) of Listeria were characterized by the polymerase chain reaction (PCR) and DNA sequencing. DNA sequencing data for the small rRNA IGS region showed that this IGS was approximately 244 bp in length and was highly homologous (95 to 99 %) in five of the six Listeria spp examined; ie., L. monocytogenes, L. innocua, L. seeligeri, L. welshimeri, and L. ivanovii. A lower degree of homology (91 to 94 %) was detected in the large rRNA IGS region (ca. 494 bp) of these species. The DNA sequence data was used to develop two sets of oligonucleotide primers for PCR-based detection of the members of the genus Listeria. The first set of primers were Listeria genus-specific and, the second set of primers were L. monocytogenes-specific. / xv, 131 leaves ; 29 cm.

Thesis (M.P.H.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 90-117). Online version available on the World Wide Web. Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2006]. 1 microfilm reel ; 35 mm.

Thesis (M.S.)--University of Delaware, 2008. / Principal faculty advisor: Kalmia Kniel, Dept. of Animal & Food Sciences. Includes bibliographical references.

Thesis (Ph.D.) in Food and Nutrition Sciences--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 150-176).

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on Sept. 21, 2009). Thesis advisor: Dr. Azlin Mustapha. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisor: Kalmia Kniel, Dept. of Animal & Food Sciences. Includes bibliographical references.

Various control methods used in the meat and poultry processing environment to mitigate listeriosis were evaluated using a dynamic in-plant Monte Carlo model. These control methods included food contact surface testing, sanitation, post-processing lethality treatment, and product formulation with microbial growth inhibitors. The dynamic in-plant model served as an input into the risk assessment model developed by the FDA and FSIS in 2003 which predicts the number of deaths and illnesses resulting from the use of each control method. The use of growth inhibitors combined with a post-processing lethality step was estimated to save over 200 more lives than the FSIS proposed minimum sampling standard. An analysis of data collected by the National Alliance for Food Safety and Security (NAFSS) found that retail-sliced deli meats have a greater prevalence and concentration of L. monocytogenes than prepackaged deli meats. Cross contamination at the retail level is suspected due to clustering of sample positives by store and the influence of sampling time of day on the prevalence of L. monocytogenes. The comparative risk of Listeria monocytogenes in retail sliced versus prepackaged deli meats was evaluated using a modified version of the 2003 FDA-FSIS risk assessment model which considered slicing location and the use of growth inhibitors. The comparative risk ratio for the number of deaths from retail-sliced versus prepackaged deli meats was found to be 9.1 and retail-sliced product with a growth inhibitor was found to be at greater risk for listeriosis than prepackaged product without growth inhibitor. / Master of Science

Hepatitis E virus (HEV), the causative agent of hepatitis E, is an emerging virus of global distribution. At least four distinct genotypes of HEV exist worldwide: genotype 1 and 2 HEV strains are responsible for waterborne epidemics; genotype 3 and 4 HEV strains are responsible for sporadic occurrences of acute hepatitis E. Genotype 3 and 4 HEVs are zoonotic and have a more expanded host range than genotypes 1 and 2 which are restricted to humans. Genotype 3 and 4 HEV isolates obtained from animal tissues are genetically very similar, or identical in some cases, to human HEV recovered from hepatitis E patients. The objectives of this dissertation research were to assess the zoonotic foodborne transmission of HEV and elucidate the viral determinants of HEV host range. To determine the risk of HEV foodborne transmission, 127 packages of commercial pig liver were tested for HEV RNA. Eleven percent of them were positive for HEV RNA and the contaminating virus remained infectious. We also demonstrated that medium-to-rare cooking condition (56°C) does not completely inactivate HEV, although frying and boiling of the contaminated livers inactivated the virus. To reduce the risk of foodborne HEV transmission, commercial pig livers must be thoroughly cooked for consumption. To determine the host range of genotype 4 HEVs, pigs were inoculated with a genotype 4 human HEV. All pigs developed an active HEV infection indicating that genotype 4 human HEVs can cross species barriers and infect pigs. To identify viral determinant(s) of species tropism, ORF2 alone or in combination with its adjacent 5′ junction region (JR) and 3′ non-coding region (NCR), were swapped between genotypes 1 and 4, 3 and 4, and 1 and 3 to produce 5 chimeric viruses. Chimeric viruses containing ORF2 or JR+ORF2+3' NCR from genotype 4 human HEV in the backbone of genotype 3 swine HEV were viable in vitro and infectious in vivo. Chimeric viruses containing the JR+ORF2+3'NCR of genotypes 3 or 4 HEV in the backbone of genotype 1 human HEV were viable in vitro but non-infectious in pigs, suggesting that ORF1 may also be important for host range. / Ph. D.

Foodborne illnesses continue to have a negative impact on the nation's health, accounting annually for an estimated 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States. Syndromic surveillance systems that analyze pre-diagnostic data, such as pharmaceutical sales data are being used to monitor diarrheal disease. The purpose of this study is to evaluate the usefulness of a poison control center (PCC) data collection and triage system for early detection of increases in foodborne illnesses.Data on calls to the Arizona Poison and Drug Information Center (APDIC) reporting suspected foodborne illnesses, and Pima County Health Department (PCHD) enteric illness reports were obtained for July 1, 2002 - June 30, 2007. Prediction algorithms were constructed using the first two and a half years, and validated in the remaining two and a half years. Multiple outcomes were assessed using unadjusted and adjusted raw counts, five and seven day moving averages, and exponentially weighted moving averages. Sensitivity analyses were conducted to evaluate model performance. Increases in PCHD laboratory reports of enteric illnesses were used as a proxy measure for foodborne disease outbreaks.Over the five year study period there were 1,094 APDIC calls reporting suspected foodborne illnesses, and 2,433 PCHD enteric illness cases. Seventy-five percent of cases were reported to PCHD within 23 days of symptom onset. In contrast, 62% of callers contacted APDIC within 24 hours of symptom onset. Forty percent of PCHD cases were missing symptom onset dates, which necessitated constructing and validating predictive algorithms using only those PCHD cases with known symptom onset dates.None of the prediction models performed at sensitivity levels considered acceptable by public health department standards. However, it is possible that a temporal relationship actually exists, but data quality (lack of outbreak dates, and missing symptom onset dates) may have prevented its detection. The study suggests that current surveillance by PCCs is insufficient as a univariate model for syndromic surveillance of diarrheal illness because of low caller volume reporting suspected foodborne illnesses; this can be improved. Methods were discussed to utilize PCCs for active surveillance of foodborne illnesses that are of public health significance.

Thesis (PhD)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Please refer to fulltext for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming