Whole genome sequencing reveals significant intra-hospital clonal transmission and a potential multidrug resistant and hypervirulent sequence cluster of <i>Corynebacterium striatum</i>

With increasing reports about <i>Corynebacteritum straitum</i>, its role as an emerging human pathogen is been recognized. However, few studies have explored the genomic epidemiology of <i>C</i>. <i>straitum</i> in China. A total of 263 isolates collected in various specimens from 2021 to 2022 were analyzed from a tertiary hospital in China. Nearly all isolates (98.5%, 259/263) were multidrug resistant (MDR). The highest resistance was observed for clindamycin (96.5%), followed by ciprofloxacin (95.0%) and erythromycin (93.5%). Genome sequencing indicated a significant prevalence of intra-hospital clonal transmission, involving six distinct clones (clone one-six). An average of 7.35 antimicrobial resistance genes and 10.65 virulence genes were identified in each strain. Genomic analysis identified a potentially hypervirulent sequence cluster (designated SC3) exhibiting near-universal carriage of four pilus assembly genes (<i>spaH</i>, <i>spaI</i>, <i>srtD</i>, and <i>srtE</i>), whereas these genes occurred at significantly lower frequencies in other sequence clusters. Further analysis estimated the emergence of SC3 strains around 1929.56 (95% HPD: 1863.41-1995.71). Phenotypic virulence assays demonstrated that <i>C. straitum</i> strains carrying the <i>spaH</i>, <i>spaI</i>, <i>srtD</i>, and <i>srtE</i> genes exhibited significantly higher virulence compared to strains lacking these genes. Our results revealed that multiple MDR <i>C</i>. <i>straitum</i> colones were circulating in the hospital. A suggestive MDR and hypervirulent SC3 was identified with potential evolutionary advantage and enhanced transmission capability.