LAUSR

PURPOSE Enterococcus faecalis is an emerging nosocomial pathogen. The study investigates the E. faecalis specific innate immune cells interplay between Natural Killer cells (NK) and Dendritic Cells (DC) in vitro. The present study also determines the prevalence, phenotype and genotype of Enterococcus faecalis isolated from paediatric patients with urinary tract infection. MATERIALS AND METHODS A total of 14 clinical isolates of Enterococcus spp were characterized using standard phenotypic tests and virulence factors were determined by polymerase chain reaction (PCR). Immature monocyte-derived DC were cultured in the presence of six pathogenic E. faecalis isolates infected DCs were co-cultured with NK cells. Bacteria induced matured DCs and activated NK cells were evaluated by polychromatic flow cytometry. RESULTS Out of 14 isolates, 13 were identified as E. faecalis. E. faecalis infected DC cells differentiated into inflammatory and CD141 + DC cells that promote NK cell activation. Activated NK cells significantly elevated the secretion of cytokines and chemokines in infected DCs during E. faecalis. This suggests that DC induced NK cell activation is effectively enhanced by the presence of E. faecalis. CONCLUSIONS Studies on virulence determinants are necessary to understand the pathogenesis of E. faecalis. DC/NK cross-talk is of particular importance at mucosal surfaces such as the intestine, urinary tract where the immune system exists in intimate association with commensal bacteria. We found E. faecalis specific NK cells activation by infected DC derived effectors signals may involve in killing of transformed or infected cells, thus coordinating innate and adaptive immune responses. E. faecalis specific DC/NK interaction is necessary for DC maturation and modulation of innate effector functions. Similarly, activated NK cells that induces maturation of DC by pattern recognition receptors is also required for generation of bacterial specific adaptive immunity.