Title page for ETD etd-07132005-161622

Type of Document Dissertation
Author da Silva, Ligia Virginia Antonia
Author's Email Address ldasil1@lsu.edu
URN etd-07132005-161622
Title Control of Vibrio vulnificus and Vibrio parahaemolyticus in Oysters
Degree Doctor of Philosophy (Ph.D.)
Department Food Science
Advisory Committee
Advisor Name Title
Marlene E. Janes Committee Chair
Donal Day Committee Member
Jon Bell Committee Member
Witoon Prinyawiwatkul Committee Member
John Supan Dean's Representative
  • bacteriophages
  • oysters
  • temperature
  • ph
  • salinity
  • liquid smoke
  • vibrio parahaemolyticus
  • vibrio vulnificus
Date of Defense 2005-07-06
Availability unrestricted
Vibrio vulnificus and Vibrio parahaemolyticus are gram-negative halophilic bacteria found in the natural aquatic environment. V. vulnifcus and V. parahaemolyticus have been implicated in foodborne illness and can cause gastroenteritis that has been associated with consumption of raw or undercooked seafood. V. vulnificus can cause primary septicemia after its ingestion, and secondary septicemia through skin lesions in individuals with preexisting conditions such as elevated serum iron levels. Bacteriophages, viruses that invade and lyse bacteria, specific to V. vulnificus and V. parahaemolyticus are naturally found in seawater and oysters.

Every summer, the oyster industry is threatened by recall of oysters due to V. vulnificus and V. parahaemolyticus contamination. Destroying these human pathogens in shell stock oysters will reduce the economic loss due to recalls and protect the oyster industry's reputation, along with the health and welfare of the consumers.

The purpose of this study was to evaluate and use different antimicrobial treatments to control Vibrio spp. in raw oysters. The use of bacteriophages active against V. vulnificus and V. parahaemolyticus was investigated. Bacteriophages against V. vulnificus, both opaque and translucent, and V. parahaemolyticus have seasonal distribution, occurring mainly in the summer months when both V. vulnificus and V. parahaemolyticus are at elevated number in oysters. Transmission electron microscopy showed that the predominant morphology of bacteriophages against V. vulnificus (opaque and translucent) and V. parahaemolyticus were icosahedra with thin flexible tail. Bacteriophages against V. vulnificus and V. parahaemolyticus lost their activity at an acidic pH. These bacteriophages were sensitive to elevated temperatures and V. parahaemolyticus bacteriophage was more salt tolerant than V. vulnificus opaque and translucent phages. The antimicrobial property of commercial smoked liquid against V. vulnificus and V. parahaemolyticus was also investigated. Hickory liquid smoke was effective in reducing V. vulnificus and V. parahaemolyticus population in laboratory media and in non-vacuum and vacuum packed oysters stored at 4C.

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