Persistent Link:
http://hdl.handle.net/10150/194128
Title:
Survival of Salmonella Newport in Oysters
Author:
Morrison, Christopher Michael
Issue Date:
2010
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Salmonella enterica is a foodborne pathogen of major significance, and as such it has been extensively studied by researchers around the world. However, despite the numerous scientific publications on Salmonella, there are still many gaps in our understanding of its biology. One such gap is in the bacteria's interactions with invertebrate hosts, and in particular, oysters. Nearly 70 million pounds of oysters are consumed in the United States each year, and previous work in the Joens' laboratory found Salmonella in roughly 7% of the market oysters they sampled, with the majority of the isolates being the Newport serovar. The majority of oysters are consumed raw, which makes the presence of Salmonella within oysters a potentially significant food safety problem.To more closely examine the interactions between Salmonella and oysters, the Present Study developed a method to consistently and reproducibly raise oysters in a controlled laboratory environment in order to systematically expose them to enteric bacteria and quantify the amount of surviving bacteria at various time points after the initial exposure. Use of this model system throughout the Present Study led to four main conclusions.The first is that Salmonella enterica serovar Newport is capable of surviving in oysters for at least 60 days, from an average concentration of 3.7x103 CFU/g of oyster meat after 10 days, to over 102 CFU/g of oyster meat after 60 days. The second main conclusion is that the Newport serovar of Salmonella, which was found in such predominance in the earlier Joens' laboratory study, does not appear to have any special adaptations for survival within oysters, as other strains of Newport and other serovars of Salmonella survived equally well within our model. The third main conclusion, based on the results of immunohistochemistry, is that the relationship between Salmonella and oysters is not a transient interaction that is limited to the outside of the oyster's gut epithelium, but involves a long-term colonization inside the oysters' connective tissues. Because the survival of Salmonella in oysters could be of a pathogenic nature, the Present Study knocked out two key type III secretion systems (T3SS) found in two distinct Salmonella pathogenicity islands (SPI-1 and SPI-2) known to be critical for pathogenesis in mammalian hosts and examined their role in the bacteria's ability to survive within oysters. The results revealed that neither the SPI-1 nor the SPI-2 T3SS were necessary for Salmonella's survival in oysters, which led to the final conclusion of the Present Study that the nature of Salmonella's infection of oysters is fundamentally different than the pathogenesis that occurs in mammalian hosts and that further study of the mechanisms of the survival of Salmonella in oysters is needed to better understand the important and interesting relationship between a significant source of food and this common, and occasionally deadly, foodborne pathogen.
Type:
text; Electronic Dissertation
Keywords:
enteric bacteria; food safety; oysters; Salmonella; shellfish
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Microbiology; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Joens, Lynn A

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleSurvival of Salmonella Newport in Oystersen_US
dc.creatorMorrison, Christopher Michaelen_US
dc.contributor.authorMorrison, Christopher Michaelen_US
dc.date.issued2010en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractSalmonella enterica is a foodborne pathogen of major significance, and as such it has been extensively studied by researchers around the world. However, despite the numerous scientific publications on Salmonella, there are still many gaps in our understanding of its biology. One such gap is in the bacteria's interactions with invertebrate hosts, and in particular, oysters. Nearly 70 million pounds of oysters are consumed in the United States each year, and previous work in the Joens' laboratory found Salmonella in roughly 7% of the market oysters they sampled, with the majority of the isolates being the Newport serovar. The majority of oysters are consumed raw, which makes the presence of Salmonella within oysters a potentially significant food safety problem.To more closely examine the interactions between Salmonella and oysters, the Present Study developed a method to consistently and reproducibly raise oysters in a controlled laboratory environment in order to systematically expose them to enteric bacteria and quantify the amount of surviving bacteria at various time points after the initial exposure. Use of this model system throughout the Present Study led to four main conclusions.The first is that Salmonella enterica serovar Newport is capable of surviving in oysters for at least 60 days, from an average concentration of 3.7x103 CFU/g of oyster meat after 10 days, to over 102 CFU/g of oyster meat after 60 days. The second main conclusion is that the Newport serovar of Salmonella, which was found in such predominance in the earlier Joens' laboratory study, does not appear to have any special adaptations for survival within oysters, as other strains of Newport and other serovars of Salmonella survived equally well within our model. The third main conclusion, based on the results of immunohistochemistry, is that the relationship between Salmonella and oysters is not a transient interaction that is limited to the outside of the oyster's gut epithelium, but involves a long-term colonization inside the oysters' connective tissues. Because the survival of Salmonella in oysters could be of a pathogenic nature, the Present Study knocked out two key type III secretion systems (T3SS) found in two distinct Salmonella pathogenicity islands (SPI-1 and SPI-2) known to be critical for pathogenesis in mammalian hosts and examined their role in the bacteria's ability to survive within oysters. The results revealed that neither the SPI-1 nor the SPI-2 T3SS were necessary for Salmonella's survival in oysters, which led to the final conclusion of the Present Study that the nature of Salmonella's infection of oysters is fundamentally different than the pathogenesis that occurs in mammalian hosts and that further study of the mechanisms of the survival of Salmonella in oysters is needed to better understand the important and interesting relationship between a significant source of food and this common, and occasionally deadly, foodborne pathogen.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectenteric bacteriaen_US
dc.subjectfood safetyen_US
dc.subjectoystersen_US
dc.subjectSalmonellaen_US
dc.subjectshellfishen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineMicrobiologyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairJoens, Lynn Aen_US
dc.contributor.committeememberJoens, Lynn A.en_US
dc.contributor.committeememberDial, Sharon Men_US
dc.contributor.committeememberLightner, Donald Ven_US
dc.contributor.committeememberViswanathan, V Ken_US
dc.contributor.committeememberDay, William Aen_US
dc.identifier.proquest11361en_US
dc.identifier.oclc752261223en_US
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