Usefulness of matrix-assisted laser desorption ionization/time of flight mass spectrometry for the identification of Streptococcus mutans.

This study evaluated the reliability of MALDI-TOF MS coupled with statistical tools for the identification of Streptococcus mutans in comparison with PCR-based techniques. Bacterial isolates were identified and serotyped by conventional PCR, using S. mutans species and serotype-specific primers. For bacterial identification, mass spectra data from S. mutans and other streptococci were compared with Biotyper V 3.1 database and the mass peak lists were examined by cluster and principal component (PCA) analysis. Identification of potential biomarkers was performed using UniProtKB/Swiss-Prot and UniProtKB/TrEMBL databases and BLAST tool of the NCBI database. PCR identified 100% of the isolates as S. mutans. S. mutans strains were typed as serotypes c (85.6%), e (8.6%), k (4.8%), and f (0.9%). Although only the 70% of the strains tested were identified at species level by the Biotyper database, PCA and cluster analysis of mass peaks allowed the identification of 100% S. mutans isolates and its differentiation from the other oral and non-oral streptococci. One mass peak at m/z value of 9572.73 was identified as species-specific biomarker for S. mutans. No biomarkers were identified for S. mutans serotypes. KEY POINTS: • MALDI-TOF MS coupled with statistical tools for the identification of S. mutans. • Detection of species identifying biomarkers by MALDI-TOF MS. • PCR identification and serotyping of S. mutans from saliva samples.

Molecular and serological typing of Streptococcus mutans strains isolated from young Galician population: relationship with the oral health status.

The aim of this study was to determine the prevalence of Streptococcus mutans and its serotypes in samples from oral cavity of young Galician population and their relationship with the oral health state. The variables generally associated with dental caries, such as salivary flow rate, buffering capacity, eating habits, and lifestyle, were also analysed. No relationship was found between the variables studied and the presence of S. mutans in the oral cavity or the existence of dental caries. Presumptive strains of S. mutans were isolated from saliva samples from 48% of the analysed population. The use of conventional microbiological methods, API 20 Strep system, and species-specific polymerase chain reaction (PCR) allowed to substantiate the identity of the strains as S. mutans. Multiplex PCR protocols, developed in this study for the simultaneous detection of S. mutans and serotypes c, e, and f and for detection of S. mutans and serotype k, also confirmed this result and demonstrated that serotype c was predominant in the studied young Galician population (86%). Serotypes e (8%), k (3%), and f (2%) were also detected. Serotype c was detected in carious and caries-free subjects, while the remaining serotypes were only found in subjects with caries.

MALDI-TOF mass spectrometry for rapid differentiation of Tenacibaculum species pathogenic for fish.

Tenacibaculosis is a fish disease that limits the culture of a variety of marine fish species of commercial value in the world. The genus Tenacibaculum includes several species, and their discrimination is of clinical interest in order to improve the management of an outbreak of the disease. In this study, a novel proteomic approach based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis was evaluated for the identification and differentiation of Tenacibaculum species. The peak mass lists derived from MALDI-TOF-MS analysis were examined for the detection of potential biomarkers, similarity and cluster analysis and principal component analysis (PCA). Culture media used for bacterial growth did not affect the mass fingerprints. Eight genus-specific peaks were found in all the Tenacibaculum species analysed. Moreover, at least one species-specific peak was found in the species Tenacibaculum maritimum, Tenacibaculum soleae, Tenacibaculum dicentrarchi, Tenacibaculum litoreum and Tenacibaculum ovolyticum. These peaks could serve as biomarkers for the rapid identification of these bacterial fish pathogens. The cluster and PCA clearly separated the species T. maritimum, T. soleae, T. dicentrarchi and T. ovolyticum in different clusters. However, species of Tenacibaculum discolor and Tenacibaculum gallaicum were difficult to distinguish based on their protein fingerprints. To our knowledge, this is the first study that deals with the characterization and determination of biomarkers of Tenacibaculum species by MALDI-TOF mass spectrometry. This approach proved to be an effective and reliable technique for the discrimination of the Tenacibaculum species; therefore, it could be integrated as a routine diagnostic tool in microbiological laboratories.