Abstract
The ability of bacteria to persist in the environment is a critical step in the transmission of many pathogens. The protozoan, Acanthamoeba is a known bacterial predator in the environment that is also host to several human pathogens, including Legionella pneumophila and enterohaemorrhagic Escherichia coli (EHEC). Recent research has shown that virulence factors required during human pathology are also crucial for the survival of these pathogens in environmental protozoans. Although significant research has been done on L. pneumophila lifestyle in protozoa, and initial research has begun on diarrheagenic EHEC, uropathogenic E. coli (UPEC) has yet to be examined. UPEC is the leading cause of community acquired urinary tract infections in the United States and accounts for 70-95% of these cases. This study examines the predator-prey interactions of Acanthamoeba castellanii and UPEC as a possible source for the environmental persistence of UPEC. The primary hypothesis of this study is that UPEC, with its suite of virulence factors, has a fitness advantage over non-pathogenic human enteric commensal E. coli when dealing with predation. The goal of this research was to determine if there are differences in fitness between uropathogenic and non-pathogenic strains of E. coli by examining populations after long-term co-culture, as well as, investigating whether Acanthamoeba can act as an environmental reservoir for UPEC. This research demonstrates that in long-term co-cultures, clinical isolates of UPEC exhibit a greater ability to survive predation with no detriment to amoebal growth. In addition, UPEC isolates demonstrated lower ability to associate with A. castellanii than the non-pathogenic E. coli, with no clinical isolate being able to survive phagocytosis by A. castellanii. Clinical isolates of UPEC had greater fitness than a non-pathogenic E. coli K-12 strain, with the enhanced fitness likely due to avoidance of predation instead of cytotoxicity towards or invasion of protozoa in a low nutrient environment.