The accession

number for Treponema pallidum was AE000520. Results Sample extraction procedure and MALDI-TOF MS measurements This study focused mainly on well-defined pathogenic leptospiral strains used for serodiagnostic purposes which belong to three genomospecies: L. interrogans, L. borgpetersenii and L. kirschneri. To complete the strain collection, analyses were also performed with intermediate and non-pathogenic strains (see Table 1). To assess the influence of the optional washing step in the sample preparation procedure for MALDI-TOF MS typing, regarding the quality of the protein spectra, we compared strains that were prepared with and without the optional additional washing step combined selleck compound with the concentrator process. No differences were found in the created protein spectra when the concentrator was used to evaporate the ethanol. However, the use of the concentrator shortened the vaporizing step to 10 minutes. When the PBS washing step was omitted, Selleck EPZ 6438 peaks representing protein sizes larger than 11,000 Da were removed (data not shown). No differences

were seen for reference spectra that were created on two different MALDI-TOF MS instruments (data not shown). To evaluate if the number of passages showed any influence on the quality of the protein spectra, measurements of Y-27632 2HCl all reference strains were applied, with cultures that were cultivated up to thirteen passages. The number of passages did not show any influence on the quality of the protein spectra (data not shown). Reference spectra database creation for MALDI-TOF MS Since the commercially available MALDI Biotyper™ database lacks leptospiral protein profiles, reference spectra were created for all 28 leptospiral strains listed in Table 1. The established database was implemented in the

reference spectra library as unassigned MSPs. Using the software MALDI Biotyper™ all 28 leptospiral protein reference spectra were visualized in a dendrogram (Figure 1). Each of the 28 strains yielded a species-specific protein profile and was clustered according to its pathogenicity in the MALDI-TOF MS dendrogram. The strains of the pathogenic Leptospira species (red color) could clearly be differentiated from the non-pathogenic Leptospira species (green color) as well as from the intermediate species (blue color). Within the pathogenic species L. borgpetersenii and L. interrogans were located in separate clusters. Discrimination was difficult for the species L. interrogans and L. kirschneri (see Figure 1). Figure 1 Dendrogram representing the protein reference spectra of the 28 leptospiral strains. blue: intermediate leptospiral strains green: non-pathogenic leptospiral strains red: pathogenic leptospiral strains.