Leptospira is a genus of gram-negative spirochete bacteria formed by free-living saprophytic or non-pathogenic species such as L. biflexa, and pathogenic species such as L. interrogans that are the etiological agents of leptospirosis [1]. The leptospiral transmission occurs through the exposure of the host to pathogenic bacteria present in soil or water contaminated with urine from chronically infected mammals [2]. The infection in humans can be asymptomatic or symptomatic with varied clinical manifestations and, in more severe cases it can lead to multiple organ failure and, consequently, to death [3,4].

This zoonosis has a worldwide prevalence, although a higher incidence occurs in tropical and subtropical countries, becoming epidemic in rainy periods especially in regions with high population concentrations and inadequate sanitation conditions [5,6]. Annually, approximately 1.03 million cases of leptospirosis and 60,000 deaths are registered [7]. It is estimated that 90% of leptospirosis cases may progress to a disease with mild symptoms and 10% of cases to severe forms which might be related to the immune status and age of the host and the type of bacteria, whether a virulent or low-virulent strain [3,8]. The growing number of human leptospirosis cases in countries located in temperate regions indicates that this zoonosis is spreading to all places characterizing it as a reemerging disease [[9], [10], [11], [12]].

The genomic sequencing of L. interrogans [13] and L. biflexa [14] were performed and comparative analysis allowed to identify some genes in the pathogenic species that are absent in the saprophytic species [14,15]. The comparison of bacterial species from different ecological niches has the potential to help to elucidate the molecular mechanisms of leptospirosis.

There are several published studies on proteomic analysis by mass spectrometry in different experimental conditions for some pathogenic leptospires species [16]. Proteomics analysis of L. interrogans serovar Pomona cultured from the kidney and liver of infected hamsters identified for the first time 286 proteins expressed using a virulent low-passage strain [17]. The global proteome of pathogenic strain L. interrogans serovar Copenhageni identified >2000 proteins, of which 1864 with the estimated number of copies per bacterial cell [18]. The comparative proteogenomic analysis between culture-attenuated IPAV and virulent 5661 strains of L. interrogans serovar Lai was performed identifying changes in the expression profile of lipoproteins and outer membrane proteins [19]. The L. interrogans serovar Copenhageni subcellular proteome fractionated by Triton X-114 resulted in more outer membrane proteins (OMPs) identified in the aqueous and pellet fractions and fewer OMPs in the detergent fraction [20].

Stewart and co-workers [21] analyzed the proteome of L. biflexa serovar Patoc during exponential growth and in the stationary phase by two-dimensional gel electrophoresis. The authors described several posttranslational modifications among membrane-associated proteins. In the current work, we present a global proteome of L. biflexa serovar Patoc strain Patoc 1, via shotgun analysis, and compared the data with the reported proteome of the pathogenic L. interrogans serovar Copenhageni strain Fiocruz L1–130. Low conserved proteins in L. biflexa or specific of L. interrogans by bioinformatics analysis were further examined by different algorithms aiming to increase the repertoire of proteins that warranted experimental studies as potential virulence factors.