Stenotrophomonas maltophilia fimbrin stimulates mouse bladder innate immune response.

The role of Stenotrophomonas maltophilia fimbrin (SMF) to stimulate the bladder innate immune response was evaluated in this study. SMF was isolated and purified from clinical isolates of S .maltophilia. Different amounts of SMF (1, 5 and 15 μg) was instilled transurethrally. The innate immune response was evaluated in terms of IL-1β, TNF-α, IL-8 and NO concentrations, and mRNA expressions of IL-1β, TNF-α, IL-8 and iNOS in mouse bladder tissue. Moreover, neutrophil infiltration in urine, myeloperoxidase (MPO) activity in bladder tissue and bladder epithelial cells (BECs) activity to engulf and kill bacteria in vitro was studied. The maximum pro-inflammatory cytokines (IL-1β and TNF-α) and chemokine (IL-8) concentrations and their mRNA expressions were found in bladder homogenates of mice that were instilled with 15 μg of SMF transurethrally. The high levels of these mediators was concomitant with the high level of neutrophil infiltration in bladder tissue (MPO) and in collected urine (neutrophil count). The administration of SMF transurethrally activated the BECs in terms of bacterial uptake and intracellular bacterial killing in vitro. This study showed that the SMF administration increased the level of nitric oxide (NO) in bladder tissue. The present study proved for the first time that the administration of mice with SMF transurethrally induced cellular and molecular elements of innate immune response in mouse bladder.