Prevotella intermedia ATCC 25611 targets host cell lamellipodia in epithelial cell adhesion and invasion

Introduction: The Prevotella intermedia group bacteria, namely P. intermedia, Prevotella nigrescens, and Prevotella pallens, are phylogenetically closely related and potentially connected with oral and gastrointestinal tract disease pathogenesis. The aim of the present study was to examine whether these species differ in their capabilities of adhesion to and invasion of epithelial cells. Methods: Adhesion and invasion were assayed by standard antibiotic/culture assays and fluorescent microscopy techniques. The effect of Prevotella strains on epithelial cell viability was measured using a commercial cell proliferation assay. Results: The strains P. intermedia ATCC 25611 and P. nigrescens ATCC 33263 adhered to epithelial cells, the adhesion numbers of P. intermedia being twice as high as those of P. nigrescens. These strains invaded epithelial cells but invasion was weak. The adhesion of P. intermedia was specifically targeted to epithelial cell lamellipodia. The number of adhered P. intermedia cells increased or decreased when the formation of lamellipodia was stimulated or inhibited, respectively. None of the tested strains showed toxic effects on epithelial cells; a clinical P. intermedia strain even increased the number of viable cells by about 20%. Conclusion: The results suggest that among the P. intermedia group bacteria, P. intermedia and P. nigrescens type strains can adhere to and invade epithelial cells, the capability of P. intermedia ATCC 25611(T)f being highest in this context. This strain proved to have a special affinity in binding to epithelial cell lamellipodia.