Staphylococcus saprophyticus is a gram-positive microorganism responsible for urinary tract infections (UTIs). Although some virulence factors are characterized, such as urease, autolysins, adhesins and hemagglutinins, large-scale proteomic studies have not been performed within this species. We performed the characterization of the exoproteome from three S. saprophyticus strains: the reference strain ATCC 15,305, a non-capsular strain 7108 and the 9325 strain containing a thick capsule which were cultured in BHI medium and culture supernatants were analysed by using mass spectrometry approach. We observed a core of 72 secreted proteins. In addition, it was possible to detect diversity in the protein profiles of the exoproteomes. 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 15,305. This result was confirmed by Western blot analysis using anti-SsaA polyclonal antibodies, and no production/ secretion of SsaA was detected in strain 7108. Transcriptional data shows that 7108 strain produces transcripts encoding SsaA, suggesting post-transcriptional regulation occurs in this strain. Moreover, when compared with the other strains that were analyzed, it was possible to detect higher levels of proteases secreted by strain 7108 and higher levels of antigenic proteins and transglycosylases secreted by 9325 strain. The results reveal diversity in protein secretion among strains. This research is an important first step towards understanding the variability in S. saprophyticus exoproteome profile and could be significant in explaining differences among strains.

腐生葡萄球菌是引起尿路感染（UTI）的革兰氏阳性微生物。尽管表征了某些毒力因子，例如脲酶，自溶素，粘附素和血凝素，但尚未在该物种内进行大规模蛋白质组学研究。我们对三个腐生葡萄球菌进行了外蛋白质组的表征菌株：在BHI培养基中培养的参考菌株ATCC 15,305，非荚膜菌株7108和含有厚胶囊的9325菌株，并通过质谱法分析培养上清液。我们观察到72种分泌蛋白的核心。另外，有可能检测外蛋白质组蛋白质谱中的多样性。有趣的是，菌株7108并未分泌三种抗原蛋白，包括经典的SsaA抗原。此外，菌株9325分泌的抗原蛋白水平高于ATCC 15,305。使用抗SsaA多克隆抗体的Western印迹分析证实了该结果，在菌株7108中未检测到SsaA的产生/分泌。转录数据显示7108菌株产生了编码SsaA的转录本，提示转录后调控发生在该菌株中。而且，当与所分析的其他菌株相比时，可以检测出菌株7108分泌的蛋白酶的更高水平和9325菌株所分泌的抗原蛋白和转糖基酶的更高水平。结果揭示了菌株之间蛋白质分泌的多样性。这项研究是迈向了解变异性的重要的第一步。腐生葡萄球菌外蛋白质组概况，可能在解释菌株之间的差异方面具有重要意义。