Synergistic findings from microbiological and evolutional analyses of virulence factors among pathogenic streptococcal species

Publication date: June 2018

Source: Journal of Oral Biosciences, Volume 60, Issue 2

Author(s): Masaya Yamaguchi

Abstract

Background

Members of the genus Streptococcus are major constituents of human skin and the mucosal microbiome, among which Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus pneumoniae are extracellular pathogens that occasionally cause life-threatening infectious diseases. Prior to their successful spread into the blood and deeper organs, pathogenic bacteria must first colonize human epithelial cell surfaces and evade host immunity. Streptococcal extracellular proteins play important roles in this colonization, as they directly interact with the host environment.

Highlight

This review focuses on recent reports of common and specific virulence factors among these species. Most streptococcal virulence factors show multiple functions. For example, conserved essential glycolytic enzymes localize on the bacterial cell surface and in the cytoplasm and contribute to evasion of host innate immunity, while bacterial glycosidases utilize host glycan via the lectin domain or glycosidase activity for survival in the host environment. Furthermore, various streptococcal species and strains show mutually exclusive interactions between the polysaccharide capsule and glycosidase. In addition, phylogenetic and evolutional analysis methods used for determining the importance of virulence factors of the species are introduced. Synergistic findings obtained by microbiological and evolutional analyses enable investigations of the consequence and correlation between genes and infectious phenotypes.

Conclusion

Bacterial pathogens rapidly adapt to clinical intervention, such as antimicrobial agents and vaccination, via horizontal gene transfer, recombination, and/or natural point mutation. It is vital to continue development of innovative analysis methods to counter the mounting threats from evolving bacteria.

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