Short communicationA lack of genetic basis for biovar differentiation in clinically important Corynebacterium diphtheriae from whole genome sequencing

•Clinical designations of Corynebacterium diphtheriae are investigated by genomics.•Sequencing of two novel C. diphtheriae was undertaken.•Comparative analysis of 17 C. diphtheriae genomes was undertaken.•The genomic basis of strain separation is shown to be more reliable than phenotypic differentiation.•Proposal that molecular characterization of strains should be adopted over phenotypic analysis.

The differentiation of clinically important Corynebacterium diphtheriae into specific biovars is complex and phylogenetically unclear. Comparative genomic analyses of 17 strains indicate that the division of C. diphtheriae into different biovars does not correlate with the variation in the gene content in the relevant metabolic categories that are potentially involved in the biovar discrimination. The biochemical separation is also not supported by phylogenetic analyses, suggesting molecular methods of typing C. diphtheriae strains should be adopted much more widely.

Graphical abstractThe differentiation of clinically important Corynebacterium diphtheriae into specific biovars is complex and phylogenetically unclear. Comparative genomic analyses of 17 strains indicate that the division of C. diphtheriae into different biovars does not correlate with the variation in the gene content in the relevant metabolic categories that are potentially involved in the biovar discrimination. The biochemical separation is also not supported by phylogenetic analyses, suggesting molecular methods of typing C. diphtheriae strains should be adopted much more widely.Download full-size image