Resumo

Staphylococcus saprophyticus is Gram-positive bacteria included in the huge set of microbial that has been described as human pathogen and associated with antimicrobial resistance. This specie is the causative agent of urinary tract infection in young healthy women. The strategies used by this pathogen to establish infection in the human host includes the secretion of antigenic proteins and virulence factors. Some recent studies analyzing secreted proteins in Staphylococcus aureus showed that proteins are differentially expressed during infection on different sites in human host. In this work, we analyzed the exoproteome of S. saprophyticus in order to identify secreted proteins. The exoproteome was obtained after 16 hours of incubation in BHI medium, followed by 3 hours of incubation in the same medium. The protein identifications were performed by using nano-ESI-UPLC-MSE (Waters) after tryptic digestion. Until this moment it was possible to identify a total of 25 proteins. Among the proteins identified there are four transglycosylases (IsaA and SceD 1-3), a bifunctional autolysin, superoxide dismutase [Mn/Fe], alkyl hydroperoxide reductase, and several proteins with unknown function. The most abundant specie protein in the S. saprophyticus exoproteome was the transglycosylase IsaA protein, that is a highly immunogenic protein described in many bacteria species, including S. aureus. The protein extract was submitted to the 2-DE-SDS-PAGE and the protein spot corresponding to IsaA was excised and used to inoculate BalbC mice to stimulate polyclonal antibodies. The antibodies specificity was checked by Western blot analysis. Furthermore, the complete exoproteome was used to inoculate BalbC mice to identify other immunogenic proteins secreted by S. saprophyticus. The polyclonal antibodies were obtained and the identification of immunogenic proteins by MALDI-Q-ToF-MS/MS is under progress. RT-qPCR experiments are under progress to evaluate the transcriptional expression identified level of the proteins identified in the exoproteome in experimental situations that mimic the host environment, such as pH conditions. In this way, our partial findings suggest that S. saprophyticus secretes immunogenic proteins that might play role in pathogenicity in the human host.