Characterizing clinically isolated Vibrio cholerae bacteriophages for the development of a phage prophylaxis cocktail
Yen, Minmin.
2016
-
Abstract: Vibrio cholerae is the causative agent of cholera, a severe diarrheal disease that is a substantial health burden on the developing world. It is a Gram-negative bacterium that lives in the aquatic ecosystem and can colonize the human small intestine upon ingestion. Virulent bacteriophages are hypothesized to play a crucial role in modulating the dynamics of cholera epidemics and the prog... read moreression of disease. Studies to date, however, have not demonstrated this in the context of human cholera infection. Therefore, the goals of my thesis are to understand the impact of intra-patient phage predation on V. cholerae population structure and how phages can be used to prevent disease. In the first study, we investigated the heterogeneity of phage resistance in Bangladeshi and Haitian stool samples containing V. cholerae and high titers of the virulent phage ICP2. Using whole-genome sequencing, we determined that ICP2 uses the major outer membrane protein OmpU as its receptor to initiate infection. The potential fitness consequences of OmpU mutants were addressed using assays measuring in vitro growth, bile sensitivity, and colonization in an infant mouse model. We were also able to recapitulate the infection dynamics thought to occur in human cholera patients that lead to the selection of OmpU mutants. Our results indicate phage pressure during infection results in an altered V. cholerae population structure that exits the host. In the second study, we determined that ICP2 is widespread in Haiti. We purified 34 ICP2 isolates from clinical samples collected from 2012 to 2014 and performed phylogenetic analyses to determine evolutionary relationships. Although there was a high degree of similarity, the relatedness does not seem to be associated with geographic location or time of isolation. In the third study, we developed a prophylactic three-phage cocktail for the prevention of cholera. Oral administration of the phages up to 24 hours before V. cholerae challenge reduced colonization of the intestinal tract and prevented the onset of disease symptoms in two animal models of cholera pathogenesis. For acute infections, such as cholera, phage prophylaxis could provide a strategy to limit the impact of bacterial disease on human health.
At the request of the author, this graduate work is not available to view in the Tufts Digital Library until February 21, 2019.
Thesis (Ph.D.)--Tufts University, 2016.
Submitted to the Dept. of Molecular Microbiology.
Advisors: Andrew Camilli, and Stephen Calderwood.
Committee: Ralph Isberg, Carol Kumamoto, and Wai-Leung Ng.
Keyword: Microbiology.read less - ID:
- zs25xm811
- To Cite:
- DCA Citation Guide EndNote
