Molecular characterization and whole-genome sequencing of Corynebacterium diphtheriae causing skin lesion.

We present a case of skin lesion caused by nontoxigenic Corynebacterium diphtheriae. Genomic taxonomy analyses corroborated the preliminary identification provided by mass spectrometry. The strain showed a susceptible phenotype with increased exposure to penicillin, the first drug of choice for the treatment. An empty type 1 class integron carrying only the sul1 gene, which encodes sulfonamide resistance, was found flanked by transposases. Virulence factors involved in adherence and iron uptake, as well as the CRISPR-Cas system, were predicted. MLST analysis revealed the ST-681, previously reported in French Guiana, a European territory.

Phenotypic and molecular characterization and complete genome sequence of a Corynebacterium diphtheriae strain isolated from cutaneous infection in an immunized individual.

Diphtheria is an infectious disease potentially fatal that constitutes a threat to global health security, with possible local and systemic manifestations that result mainly from the production of diphtheria toxin (DT). In the present work, we report a case of infection by Corynebacterium diphtheriae in a cutaneous lesion of a fully immunized individual and provided an analysis of the complete genome of the isolate. The clinical isolate was first identified by MALDI-TOF Mass Spectrometry. The commercial strip system and mPCR performed phenotypic and genotypic characterization, respectively. The antimicrobial susceptibility profile was determined by the disk diffusion method. Additionally, genomic DNA was sequenced and analyzed for species confirmation and sequence type (ST) determination. Detection of resistance and virulence genes was performed by comparisons against ResFinder and VFDB databases. The isolate was identified as a nontoxigenic C. diphtheriae biovar Gravis strain. Its genome presented a size of 2.46 Mbp and a G + C content of 53.5%. Ribosomal Multilocus Sequence Typing (rMLST) allowed the confirmation of species as C. diphtheriae with 100% identity. DDH in silico corroborated this identification. Moreover, MLST analyses revealed that the isolate belongs to ST-536. No resistance genes were predicted or mutations detected in antimicrobial-related genes. On the other hand, virulence genes, mostly involved in iron uptake and adherence, were found. Presently, we provided sufficient clinical data regarding the C. diphtheriae cutaneous infection in addition to the phenotypic and genomic data of the isolate. Our results indicate a possible circulation of ST-536 in Brazil, causing cutaneous infection. Considering that cases of C. diphtheriae infections, as well as diphtheria outbreaks, have still been reported in several regions of the world, studies focusing on taxonomic analyzes and predictions of resistance genes may help to improve the diagnosis and to monitor the propagation of resistant clones. In addition, they can contribute to understanding the association between variation in genetic factors and resistance to antimicrobials.