Characterizing clinically isolated Vibrio cholerae bacteriophages for the development of a phage prophylaxis cocktail
Yen, Minmin.
2016
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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 ... read moreprogression 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.
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
- Component ID:
- tufts:20680
- To Cite:
- DCA Citation Guide EndNote
