Description of some coryneform bacteria isolated from human clinical specimens as Corynebacterium falsenii sp. nov.

This study describes four yellowish-pigmented coryneform bacterial strains isolated from normally sterile human body fluids between 1991 and 1995. Initially designated EF group 42 bacteria, these isolates could not be classified into any established Corynebacterium taxon. Using a polyphasic approach combining phenotypic and molecular methods, researchers characterized the strains through biochemical profiling, antimicrobial susceptibility testing, protein analysis, chemotaxonomy, and 16S rRNA gene sequencing. Key distinguishing features included weak pyrazinamidase and urease activities, slow fermentative acid production from glucose, and distinctive yellowish pigmentation. Whole-cell protein analysis via SDS-PAGE demonstrated all four strains represented a homogeneous group with greater than 70% within-group correlation. Chemotaxonomic analysis confirmed assignment to genus Corynebacterium based on cellular fatty acid patterns and presence of meso-diaminopimelic acid in cell walls. Comparative 16S rRNA sequence analysis revealed 100% sequence identity among the four isolates and approximately 2% divergence from their closest relative, Corynebacterium jeikeium. Based on these phenotypic and genealogical distinctions, the authors propose a new species designation: Corynebacterium falsenii sp. nov., with type strain CCUG 33651.

Key findings

• Four phenotypically and genetically identical yellowish-pigmented coryneform strains isolated from normally sterile human body sites were identified as a novel Corynebacterium species
• C. falsenii is distinguished by weak pyrazinamidase activity, delayed urease activity, slow fermentative acid production from glucose, and yellowish pigmentation after 72 hours incubation
• 16S rRNA sequence analysis showed the four strains had 100% identity with each other and approximately 2% divergence from C. jeikeium, their nearest phylogenetic relative
• Chemotaxonomic analysis confirmed genus Corynebacterium assignment through characteristic cellular fatty acid profiles and presence of meso-diaminopimelic acid and mycolic acids