Population structure and antimicrobial resistance of Corynebacterium diphtheriae in Victoria, Australia

Abstract

Corynebacterium diphtheriae, the main aetiological agent of diphtheria, is a re-emerging bacterial pathogen of public health concern, yet remains largely understudied globally. In this study, we analysed the population structure and anti-microbial resistance (AMR) of 210 C. diphtheriae isolates from Victoria, Australia, including 103 historical (1950–1970) and 107 contemporary clinical isolates (2004–2023), using whole-genome sequencing and phenotypic susceptibility testing. The diphtheria toxin gene (tox) was detected in 89 isolates, the majority of which (n=83; 93.3%) were historical. Population structure comprised two primary phylogenetic lineages, Mitis and Gravis, each containing multip..