Defense Date


Document Type


Degree Name

Doctor of Philosophy


Microbiology & Immunology

First Advisor

Denise Toney


Foodborne illnesses are a significant public health challenge in the United States, with an estimated 9.4 million illnesses annually attributed to the consumption of contaminated food, of which 59% are estimated to be caused by viruses, 39% by bacteria and 2% by parasites. Timely detection and identification of the pathogens causing foodborne outbreaks is vital for the implementation of outbreak control strategies, allowing public health officials to prevent additional illnesses and maintain confidence in the food supply. Public health laboratories employ a variety of traditional and molecular testing techniques to identify foodborne outbreak etiologic agents. One technology is the Luminex XMap® microsphere system, which is also marketed as the Bio-Plex™ 200. This platform has a multiplexing capability with the potential to simultaneously detect up to 100 targets in one reaction. The studies described here show that the combination of two Bio-Plex assays with real-time virus assays and one extraction method provides a flexible foodborne outbreak screening algorithm that potentially identifies an outbreak-associated pathogen on the first day of specimen submission and aids in focusing confirmatory laboratory testing. In these studies, two microsphere-based assays were designed for use on the Bio-Plex 200 system as screening assays for the detection of four enteric protozoa (Giardia intestinalis, Cyclospora cayetanensis, Cryptosporidium parvum, Entamoeba histolytica) and six virulence determinants of shiga toxin-producing Escherichia coli (STEC), enterotoxigenic Escherichia coli (ETEC), enteroinvasive Escherichia coli (EIEC) and Shigella spp. Precision and limits of detections were established for both assays. The sensitivity and specificity of the protozoan assay as compared to reference methods ranged from 81.25% to 100% for most targets, while sensitivity for the E. histolytica target was 42.86%. Sensitivity and specificity for the bacterial assay was 100% as compared to reference methods. However, cross-reactivity of the protozoan assay E. histolytica target with E. dispar and of the bacterial assay uidA target with enteropathogenic E. coli strains was noted. Additionally, real-time detection of norovirus and rotavirus nucleic acids extracted with the QIAamp DNA Stool Mini Kit was statistically comparable to detection when extracted with the Ambion® MagMAX™-96 Viral RNA Isolation Kit combined with the KingFisher® Magnetic Particle Processor.


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VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

August 2011