Genomic characterization of Corynebacterium diphtheriae isolates from human origin in Brazil, 1974-2024

Introduction Diphtheria is a potentially fatal disease that still causes deaths mainly in unvaccinated children. Over the last decades, the incidence of this disease has reduced drastically in face to the increase in vaccination coverage. Diphtheria is mainly caused by toxigenic Corynebacterium diphtheriae , however, in more recent years, invasive infections due to nontoxigenic Corynebacterium diphtheriae have emerged. Given this epidemiological threat, the continued surveillance remains essential to guide prevention and control measures. Methodology Using whole genome sequencing, we characterized 299 Corynebacterium diphtheriae isolates, assessing their clinical origin, age distribution of patients, tox gene carriage, antimicrobial resistance markers, and phylogenetic relationships. Results The tox gene was identified in 255 isolates (85.3%). Antimicrobial resistance genes aph(3’’)-Ib , aph(3’)-Ia , aph(6)Id , cmx , tet(33) , tet(O) , tet(W) , and tet(Z) were detected in low (