Characterization of a Highly Virulent Strain Isolated from a Preterm Infant with Sepsis.

PURPOSE

is an opportunistic pathogen that causes an increasing number of serious infections. This study aimed to investigate the etiology of the severe clinical symptoms of sepsis in preterm infants and the characterization of isolates.

PATIENTS AND METHODS

Whole-genome sequencing (WGS) was performed on three strains isolated from an infected preterm infant. Additionally, the genomic sequences of 534 strains were obtained from the NCBI database. To gain deeper insights into these strains, we utilized the Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Clusters of Orthologous Groups (COG), and Pathogen Host Interactions (PHI) database annotation tools for comprehensive gene function analyses. Moreover, the multilocus sequence typing (MLST), EasyCGtree, and virulence factor database (VFDB) were employed to determine the sequence types (STs), construct phylogenetic trees, and identify potential virulence factors.

RESULTS

Sequence analysis found that the three isolated strains had identical sequence characteristics and did not correspond to any of the known ST types. Virulence factor analysis revealed that the three strains harbored , and capsule genes. These virulence factors are likely to play crucial roles in enhancing adhesion and metabolic capabilities, resisting phagocytosis (inducing immune cell damage), and ultimately contributing to prolonged bacteremia. The phylogenetic tree and comparative genomics of virulence factors showed the genetic and virulence factor diversity of the currently reported strains.

CONCLUSION

We identified a novel strain of that exhibits high virulence and leads to severe septicemia phenotypes in preterm infants. Furthermore, comparative genomic analysis of previously reported strains revealed the existence of three clades. This comprehensive analysis provides novel insights into the genetic relationships and virulence factor profiles of diverse strains of . In future, it will be necessary to investigate the concept of the high virulence of to determine the treatment method.