ABSTRACT
Gram-positive anaerobic cocci (GPAC) account for 24%-31% of the anaerobic bacteria isolated from human clinical specimens. At present, GPAC are under-represented in the Biotyper MALDI-TOF MS database. Profiles of new species have yet to be added. We present the optimization of the matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) database for the identification of GPAC. Main spectral profiles (MSPs) were created for 108 clinical GPAC isolates. Identity was confirmed using 16S rRNA gene sequencing. Species identification was considered to be reliable if the sequence similarity with its closest relative was ≥98.7%. The optimized database was validated using 140 clinical isolates. The 16S rRNA sequencing identity was compared with the MALDI-TOF MS result. MSPs were added from 17 species that were not yet represented in the MALDI-TOF MS database or were under-represented (fewer than five MSPs). This resulted in an increase from 53.6% (75/140) to 82.1% (115/140) of GPAC isolates that could be identified at the species level using MALDI-TOF MS. An improved log score was obtained for 51.4% (72/140) of the strains. For strains with a sequence similarity <98.7% with their closest relative (n = 5) or with an inconclusive sequence identity (n = 4), no identification was obtained by MALDI-TOF MS or in the latter case an identity with one of its relatives. For some species the MSP of the type strain was not part of the confined cluster of the corresponding clinical isolates. Also, not all species formed a homogeneous cluster. It emphasizes the necessity of adding sufficient MSPs of human clinical isolates.
Subject(s)
Bacteria, Anaerobic/classification , Gram-Positive Bacteria/classification , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization , Bacteria, Anaerobic/genetics , Bacterial Typing Techniques , Databases, Factual , Gram-Positive Bacteria/genetics , Humans , Phylogeny , RNA, Ribosomal, 16S/genetics , Reproducibility of Results , Sequence Analysis, DNA , Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methodsABSTRACT
We describe a new Anaerococcus species isolated from human clinical specimens. Analyses of 16S rRNA gene sequences of three strains showed <98% similarity with its closest relative Anaerococcus octavius. Phylogenetically the isolated strains form a cluster and can be differentiated from other species of the genus Anaerococcus based on its phenotypic characteristics and its MALDI-TOF MS profile. We propose the name Anaerococcus nagyae, with A. nagyae DSM101193 (accession number KU043522) as the type strain.
