Diversity of β-hemolysins produced by the human opportunistic streptococci
Atsushi Tabata1, Hideaki Nagamune1
1Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University Graduate School, Tokushima, Japan.
Abstract:
The genus Streptococcus infects a broad range of hosts, including humans. Some species, such as S. pyogenes, S. agalactiae, S. pneumoniae, and S. mutans, are recognized as the major human pathogens, and their pathogenicity toward humans has been investigated. However, many of other streptococcal species have been recognized as opportunistic pathogens in humans, and their clinical importance has been underestimated. In our previous study, the Anginosus group streptococci (AGS) and Mitis group streptococci (MGS) showed clear β-hemolysis on blood agar, and the factors responsible for the hemolysis were homologs of two types of β-hemolysins, cholesterol-dependent cytolysin (CDC) and streptolysin S (SLS). In contrast to the regular β-hemolysins produced by streptococci (typical CDCs and SLSs), genetically, structurally, and functionally atypical β-hemolysins have been observed in AGS and MGS. These atypical β-hemolysins are thought to affect and contribute to the pathogenic potential of opportunistic streptococci mainly inhabiting the human oral cavity. In this review, we introduce the diverse characteristics of β-hemolysin produced by opportunistic streptococci, focusing on the species/strains belonging to AGS and MGS, and discuss their pathogenic potential.
Insights
Opportunistic streptococci, including Anginosus and Mitis groups, produce atypical beta-hemolysins. These toxins contribute to the pathogenic potential of these underappreciated human pathogens.
Area of Science:
- Microbiology
- Pathogenesis
- Bacterial Toxinology
Background:
- The genus Streptococcus comprises major human pathogens and numerous opportunistic species.
- The clinical significance of many opportunistic streptococci remains underestimated.
- Previous work identified beta-hemolysins in Anginosus group streptococci (AGS) and Mitis group streptococci (MGS) as homologs of cholesterol-dependent cytolysin (CDC) and streptolysin S (SLS).
Purpose of the Study:
- To review the diverse characteristics of beta-hemolysins produced by opportunistic streptococci.
- To focus on species and strains within AGS and MGS.
- To discuss the pathogenic potential of these atypical beta-hemolysins.
Main Methods:
- Literature review of studies on beta-hemolysins in opportunistic streptococci.
- Analysis of genetic, structural, and functional properties of identified hemolysins.
- Comparison of atypical hemolysins with typical CDCs and SLSs.
Main Results:
- Atypical beta-hemolysins, distinct from typical CDCs and SLSs, are produced by AGS and MGS.
- These atypical hemolysins exhibit diverse genetic, structural, and functional characteristics.
- The identified hemolysins are associated with the pathogenic potential of these opportunistic bacteria.
Conclusions:
- Opportunistic streptococci, particularly AGS and MGS, possess unique beta-hemolysins.
- These atypical hemolysins play a role in the pathogenicity of streptococci inhabiting the human oral cavity.
- Further research is warranted to fully elucidate the clinical importance of these toxins.
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