Doctor of Philosophy (PhD)
School of Nutrition and Food Sciences
Members of the genus Vibrio are Gram-negative, halophilic bacteria that inhabit warm coastal and estuarine waters worldwide. Among pathogenic vibrios, Vibrio parahaemolyticus is the leading cause of seafood-related illnesses and Vibrio vulnificus causes the highest number of seafood-related deaths in the United States. Moreover, according to the U.S. Centers for Disease Control and Prevention, the incidence of infections of the two vibrios due to the consumption of oysters has shown a sustained increase since 2001, indicating further measures are needed to prevent human Vibrio illness. In this dissertation research, a total of 622 Vibrio isolates, consisting of 252 V. parahaemolyticus and 370 V. vulnificus, were recovered from 82 Louisiana Gulf and retail raw oysters between 2005 and 2006. A selected subset of the isolates (168 V. parahaemolyticus and 151 V. vulnificus) was determined for antimicrobial susceptibility profiles. In addition, V. vulnificus isolates (n = 349) were characterized by the presence/absence of a viuB-associated fragment and genotypes of three biomarkers: the virulence-correlated gene (vcg), 16S rRNA, and the capsular polysaccharide operon (CPS). Then multiplex PCR assays using three biomarkers: vcg, 16S rRNA and CPS, as well as species-specific vvhA were developed to simultaneously detect and characterize V. vulnificus. Finally, loop-mediated isothermal amplification (LAMP) assays were developed and evaluated to detect total or virulent-type V. vulnificus in raw oysters. Compared to PCR, LAMP assay developed were highly specific, sensitive and quantitative. The dissertation research provided comprehensive information on the genotypes, population dynamics, and antimicrobial resistance profiles of the two important vibrios. The rapid, specific, sensitive, and cost-effective molecular detection assays developed provided invaluable tools for the regulatory agencies and seafood industry to facilitate better control of Vibrio in seafood, therefore reducing the incidence of foodborne illnesses and deaths resulted from the consumption of raw oysters.
Document Availability at the Time of Submission
Release the entire work immediately for access worldwide.
Han, Feifei, "Antimicrobial Susceptibility, Genotypic Characterization, and Molecular Detection of Vibrio parahaemolyticus and Vibrio vulnificus from Louisiana Oysters" (2010). LSU Doctoral Dissertations. 2549.