Thesis
Genetically and biochemically distinct Yersinia pestis strains exhibit distinct Xenopsylla cheopis flea colonization phenotypes, but comparable transmission efficiency
Washington State University
Master of Science (MS), Washington State University
12/2019
DOI:
https://doi.org/10.7273/000000051
Handle:
https://hdl.handle.net/2376/119272
Abstract
Yersinia pestis is the flea-transmitted etiologic agent of bubonic plague. Sylvatic
plague ecology is highly complex, consisting of diverse flea and rodent species and
pathogen strains. Transmission by flea bite primarily occurs via the Y. pestis biofilmmediated foregut blockage and regurgitation mechanism, which has been largely
detailed by studies in the single model interaction between Y. pestis KIM6+ and
Xenopylla cheopis. Whether pathogen specific traits influence this interaction is
unknown, but important considering the diversity of Y. pestis strains and vector
competencies. In this study, the ability to proliferate and develop foregut blockage in X.
cheopis fleas was compared between two distinct Y. pestis strains KIM6+ (biovar
Medievalis, glycerol fermentation positive) and CO92 (biovar Orientalis, glycerol
fermentation negative), and a CO92 strain functionally restored for glycerol fermentation (CO92gly). Orientalis biovar strains are specifically implicated in historic plague
pandemics, globally distributed, and cause contemporary epidemics. Our data
demonstrates that KIM6+ and CO92 strains develop foregut blockage at similar rates
and temporal incidences, but the CO92gly strain shows significantly greater blockage
rates and advanced temporal blockage incidence. In contrast, the KIM6+ strain
exhibited faster growth and two-fold higher burdens per flea, with a distinctive foregut
colonization extending the length of the esophagus in ~65% of blocked fleas, in contrast
to 32% and 26%, respectively, in fleas blocked with CO92 and CO92gly. The proximity
of bacteria to the flea mouthparts did not result in greater numbers of bacteria being
regurgitated by KIM6+ infected fleas; all three strains showed variable numbers of Y.
pestis transmission, but we observed a tendency for CO92gly to transmit fewer bacteria.
Higher blockage rates are tantamount to effective transmission, yet lower transmission
rates and absence of naturally occurring CO92gly-like strains confounds this concept
and prompted us to test CO92gly competitive fitness. Co-infection of fleas with the
parental CO92 strain revealed a gross fitness attenuation of CO92gly, suggesting that
glycerol fermentation within the genetic context of CO92 is a fitness cost. Our study
suggests that extant Y. pestis genotypes cumulatively accommodate comparable
transmission efficiencies as it is of paramount importance to maintain pathogen spread
from many competent flea vectors.
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Details
- Title
- Genetically and biochemically distinct Yersinia pestis strains exhibit distinct Xenopsylla cheopis flea colonization phenotypes, but comparable transmission efficiency
- Creators
- Athena Kostrubala Lemon
- Contributors
- VIVEKA VADYVALOO (Degree Supervisor) - Washington State University, Paul G. Allen School for Global Animal HealthKELLY A. BRAYTON (Committee Member) - Washington State University, Veterinary Microbiology and Pathology, Department ofDANA KATHLEEN SHAW (Committee Member) - Washington State University, Veterinary Microbiology and Pathology, Department of
- Awarding Institution
- Washington State University
- Academic Unit
- Veterinary Medicine, College of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Format
- pdf
- Number of pages
- 54
- Identifiers
- 99900590461401842
- Language
- English
- Resource Type
- Thesis