Pathogen-pathogen interactions: a comparative study of Escherichia coli interactions with the clinical and environmental isolates of Acanthamoeba

In this study, we compared the interactions of invasive and non-invasive strains of E. coli with clinical and environmental isolates of Acanthamoeba. The environmental isolate of Acanthamoeba exhibited significantly higher association with E. coli compared with the clinical isolates of Acanthamoeba. The ratio of E. coli per amoebae was more than 8-fold higher in the environmental isolate compared with the clinical isolates of Acanthamoeba. Interestingly, non-pathogenic environmental Acanthamoeba showed uptake and/or survival of the non-invasive E. coli. In contrast, clinical isolates of Acanthamoeba did not support uptake and/or survival of non-invasive E. coli. Using several mutants derived from K1, we demonstrated that outer membrane protein A (OmpA) and lipopolysaccharide (LPS) are crucial bacterial determinants responsible for E. coli K1 interactions and in the intracellular survival of E. coli in Acanthamoeba. The use of Acanthamoeba as a model to study E. coli K1 pathogenesis and to understand bacterial immune evasion strategies is discussed further.