Date of Award

5-2016

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Microbiology

Committee Member

Dr. Tamara McNealy, Committee Chair

Committee Member

Dr. Claressa Lucas

Committee Member

Dr. Terri Bruce

Committee Member

Dr. Lesly Temesvari

Abstract

Legionella is the causative agent Legionnaires’ Disease and the number one cause of bacterial water-borne outbreaks in the United States. 85% of Legionnaires’ Disease cases are attributed to one species, L. pneumophila. Other virulent Legionella species exist, yet we have limited knowledge of them. Four non-pneumophila species: L. clemsonensis, L. gormanii, L. anisa, and the uncharacterized strain D4482, were chosen to assess host interactions with two species of amoebae, Acanthamoeba polyphaga and A. castellanii. Interactions were assessed with both planktonic, amoebae grown and biofilm Legionella. For planktonic assays, L. pneumophila invaded significantly higher into A. castellanii than into A. polyphaga. Invasion of L. pneumophila was also higher than the four non-pneumophila species in both Acanthamoebae species. Amoebae grown L. clemsonensis showed an increased invasion ability compared to broth grown in A. castellanii. Both A. polyphaga and A. castellanii grazed equally from all Legionella biofilms started from planktonic culture. When amoebae grown bacteria were used to establish biofilms, L. pneumophila, L. gormanii, and L. anisa were grazed at lower amounts by Acanthamoebae than planktonically grown biofilms. Our results suggest that the Acanthamoebae host shows no preference for the Legionella species it consumes and that growth within an amoebae affects the host interaction. Characterization of host-pathogen interactions can aid in creating improved understanding of the microbial ecology and in turn predictive risk assessment for Legionella.

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