title: Identification of Staphylococcus intermedius Group by MALDI-TOF MS.
abstract: The Staphylococcus intermedius Group includes S. intermedius, S. pseudintermedius and S. delphini, coagulase-positive bacteria commonly isolated from animals. The identification of organisms belonging to this group is presently carried out using molecular methods. This study assessed the suitability of MALDI-TOF MS for their identification. 69 strains of different biological and geographic origins, identified by partial hsp60 gene sequencing as S. intermedius (n=15), S. pseudintermedius (n=32) and S. delphini (n=22), were analyzed by MALDI-TOF MS. The estimated sensitivity, specificity and efficiency were calculated. In addition we computed the agreement between the outcome of MALDI-TOF MS identification and partial hsp60 gene sequencing. The sensitivity of MALDI-TOF MS was higher for S. intermedius [0.95 (95% CI: 0.68-0.99)], than for S. pseudintermedius [0.78 (95% CI: 0.60-0.90)] and S. delphini [0.64 (95% CI: 0.41-0.83)], whereas the specificity was 1 for S. intermedius and S. delphini and 0.97 (95% CI: 0.86-0.99) for S. pseudintermedius. The Cohen's kappa coefficient indicated almost perfect agreement between MALDI-TOF MS and hsp60 gene sequencing for the identification of S. intermedius [0.96 (95% CI: 0.87-1.04)], and substantial agreement for S. delphini and S. pseudintermedius [0.70 (95% CI: 0.52-0.89) and 0.76 (95% CI: 0.616-0.92), respectively]. The overall efficiency of the proteomic identification ranged between 0.88 (95% CI: 0.78-0.95) for S. pseudintermedius and S. delphini and 0.99 (95% CI: 0.92-0.99) for S. intermedius. MALDI-TOF MS is thus a valuable and reliable tool for the rapid and accurate identification of bacteria belonging to the S. intermedius Group.
authors.affiliation: Cantonal Institute of Microbiology, 6500 Bellinzona, Switzerland. paola.decristophoris@ti.ch
authors.forename: Paola
authors.initials: P
authors.lastname: Decristophoris
authors.forename: Amy
authors.initials: A
authors.lastname: Fasola
authors.forename: Cinzia
authors.initials: C
authors.lastname: Benagli
authors.forename: Mauro
authors.initials: M
authors.lastname: Tonolla
authors.forename: Orlando
authors.initials: O
authors.lastname: Petrini
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D001431:Bacteriological Techniques / Q000379:methods*; D018834:Chaperonin 60 / Q000235:genetics; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013210:Staphylococcus / Q000737:chemistry* / Q000145:classification*
chemical_list: D001426:Bacterial Proteins; D018834:Chaperonin 60; D004269:DNA, Bacterial