Comparative analysis of 31 Streptococcus gallolyticus strains uncovers their potential risks from the perspectives of virulence factors and antibiotic resistance genes

Abstract

Streptococcus gallolyticus is an opportunistic pathogen and plays important role in various ecological niches, particularly in the intestinal tract of mammals. Obtaining the composition of S. gallolyticus strains from multiple perspectives is beneficial to broadening the knowledge of S. gallolyticus. Hence, we collected the genomic datasets of 31 S. gallolyticus strains and conducted the pan-genome analysis to systemically illustrate the genetic features and investigate the mechanism of its pathogenicity. Our results showed that the pan-genome of S. gallolyticus is composed of 4,606 homologous clusters and presented an open pan-genome structure. The phylogenetic analysis revealed the complicated relationship among S. gallolyticus strains. Six CAZyme families were identified from 182 orthologous genes that mainly derived from the core genome to clarify the carbohydrate metabolism of S. gallolyticus strains. The results showed that the metabolic ability of carbohydrates of 31 S. gallolyticus strains was different and these strains preferred glycosides and a crucial influence on the formation and modification of glycans and glycoconjugates. Particularly, the results of virulence factors indicated that the pathogenicity of S. gallolyticus strains was related to immunity, bile acid metabolism, and membrane synthesis. Besides, to guide the clinical treatment, we investigated the composition of antibiotic resistance genes of S. gallolyticus strains and claimed that these strains are resistant to antibiotics. Overall, our work systematically explores the genetic background of S. gallolyticus, provides an in-depth understanding of the biological characteristics of S. gallolyticus, and sheds light on the clinical detection and prevention of S. gallolyticus.