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

With increasing reports about Corynebacteritum straitum, its role as an emerging human pathogen is been recognized. However, few studies have explored the genomic epidemiology of C. straitum 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 (spaH, spaI, srtD, and srtE), 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 C. straitum strains carrying the spaH, spaI, srtD, and srtE genes exhibited significantly higher virulence compared to strains lacking these genes. Our results revealed that multiple MDR C. straitum colones were circulating in the hospital. A suggestive MDR and hypervirulent SC3 was identified with potential evolutionary advantage and enhanced transmission capability.