title: Identification of Lactobacilli from deep carious lesions by means of species-specific PCR and MALDI-TOF mass spectrometry.
abstract: BACKGROUND
  The aim of the present study was to compare MALDI-TOF results for the identification of 87 lactobacilli, isolated from soft or hard carious dentin from 70 first molars of 7- to 8-year-old children with those obtained by species-specific PCR.
  
  
  METHODS
  The 87 isolates were analyzed by MALDI-TOF MS (Microflex LT, MALDI Biotyper 3.0, Bruker Daltonik, Bremen, Germany), using a reference data base of 4110 strains including > 90 lactobacillus species. For the identification with species-specific PCR, oligonucleotide primers (16S rRNA) specific for L. casei, L. paracasei, L. rhamnosus, L. gasseri, L. plantarum, and L. acidophilus were used; type strains served as controls. The PCR-products were separated electrophoretically on a 1.5% agarose gel and identified by their position on the gel.
  
  
  RESULTS
  For 93% of the strains both methods produced concordant results: 40 strains were identified as L. rhamnosus, 16 as L. paracasei subsp. paracasei, 15 as L. paracasei subsp. tolerans, 4 as L. paracasei, 3 as L. gasseri, 2 as L. plantarum, and 1 as L. casei. In 4.5% of the cases the results were discordant. Of the 3 strains, not identified by species-specific PCR, 1 strain was identified by MALDI-TOF MS as L. spec. and 1 as L. parabuchneri. One strain could not be identified by either method.
  
  
  CONCLUSIONS
  Both methods are highly sensitive. Limitations can be the precision of the primers (PCR) or the scarcity of strains from a certain habitat in the data base. Additional information is necessary for the strains without or with discordant identification.
authors.affiliation: Department of Operative Dentistry, University Medical Center, Johannes Gutenberg University, Mainz, Germany. callaway@uni-mainz.de
authors.forename: Angelika
authors.initials: A
authors.lastname: Callaway
authors.affiliation: Bruker Daltonik GmbH Bremen, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kostrzewa
authors.affiliation: Department of Operative Dentistry, University Medical Center, Johannes Gutenberg University, Mainz, Germany.
authors.forename: Brita
authors.initials: B
authors.lastname: Willershausen
authors.affiliation: Interfaculty Institute of Genetics and Functional Genomics, Ernst-Moritz-Arndt University, Greifswald, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Schmidt
authors.affiliation: The Biotechnology Center of Oslo, University of Oslo, Norway.
authors.forename: Bernd
authors.initials: B
authors.lastname: Thiede
authors.affiliation: Biological Laboratory, Center of Dentistry, Hospital Jena, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Küpper
authors.affiliation: Biological Laboratory, Center of Dentistry, Hospital Jena, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Kneist
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D003731:Dental Caries / Q000382:microbiology*; D006801:Humans; D007778:Lactobacillus / Q000145:classification / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*; D013045:Species Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D017931:DNA Primers