Project description:Staphylococcus saprophyticus is a gram-positive microorganism responsible for urinary tract infections (UTIs). Although some virulence factors have been characterized, such as urease, autolysins, adhesins, hemagglutinins and cell wall proteins, large-scale proteomic studies have not been performed within this species. In our research, we performed the characterization of the exoproteome from three clinical S. saprophyticus strains (ATCC 15305-capsular strain, 7108 non-capsular strain and 9325, a strain containing a thick capsule) which were cultured until the stationary phase of bacterial growth by using mass spectrometry approach. In these strains we observed a core of 72 secreted proteins. In addition, we identified proteins that were not secreted by all the strains. It was possible to detect diversity in the protein profiles of the exoproteomes, and consequently proteins that were differentially expressed were identified. Interestingly, strain 7108 presented no secretion of three antigenic proteins, including the classical SsaA antigen. In addition, the level of antigenic proteins secreted by strain 9325 was higher than in ATCC 15305. This result was confirmed by Western blot analysis using anti-SsaA polyclonal antibodies, and no production or secretion of SsaA was detected in strain 7108. Moreover, when compared with the other strains that were analyzed, it was possible to detect higher levels of proteases secreted by strain 7108. The results reveal diversity in protein secretion among strains. This research is an important first step towards understanding the variability in S. saprophyticus and could be significant in explaining differences in virulence.