Characterization of Corynebacterium species isolated from nasal swabs of healthy volunteers: description of Corynebacterium nasorum sp. nov., Corynebacterium tardum sp. nov., Corynebacterium tuingiense sp. nov., Corynebacterium limaceinasi sp. nov. and Corynebacterium kefirresidentii sp. nov.

Members of the genus Corynebacterium are common constituents of the human nasal microbiota but their cultivable diversity remains incompletely represented in taxonomic and diagnostic databases. Ten coryneform strains isolated from nasal swabs of seven healthy adults were characterized using matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (MALDI-TOF MS), whole-genome sequencing, phylogenomic inference, overall genome relatedness indices, phenotypic testing and chemotaxonomic analyses. MALDI-TOF MS initially assigned most strains to Corynebacterium tuberculostearicum or Corynebacterium accolens , whereas genome-based analyses resolved the strains into five distinct species-level lineages. The lineages represented by strains LaCa116 T , LaCa142 T and LaCa191 T were clearly differentiated from their closest related type strains by average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values below accepted species-level thresholds. Strains LaCa7 T and LaCa117 T represented closely related but distinguishable genomic lineages, with an ANI value of 95.9% and a dDDH value of 66.4%. Strain LaCa117 T was closely related to strain SB, to which the effectively but not validly published name ‘ Corynebacterium kefirresidentii ’ had previously been applied. Phenotypic and chemotaxonomic characteristics supported the genomic groupings and placement of the strains within the genus Corynebacterium . These findings reveal previously unrecognized diversity among cultivable nasal corynebacteria and demonstrate that routine MALDI-TOF MS identification may be unreliable when suitable reference spectra are absent. Based on the integrated taxonomic evidence, the names Corynebacterium nasorum sp. nov. (type strain LaCa7 T =DSM 119349 T =LMG 33882 T ), Corynebacterium kefirresidentii sp. nov. (type strain LaCa117 T =DSM 119343 T =LMG 33886 T ), Corynebacterium tuingiense sp. nov. (type strain LaCa142 T =DSM 119342 T =LMG 33884 T ), Corynebacterium limaceinasi sp. nov. (type strain LaCa191 T =DSM 119341 T =LMG 33883 T ) and Corynebacterium tardum sp. nov. (type strain LaCa116 T =DSM 119344 T =LMG 33885 T ) are proposed.