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Genome Mining and Comparative Analysis of Streptococcus intermedius Causing Brain Abscess in a Child
Elio Issa1, Tamara Salloum2, Balig Panossian3
1Department of Natural Sciences, School of Arts and Sciences, Lebanese American University, Byblos 36, Lebanon. elio.issa@lau.edu.
Pathogens (Basel, Switzerland)
|February 21, 2019
Summary
Streptococcus intermedius causes severe infections like brain abscess. This study reveals novel genetic insights into its virulence, including the type seven secretion system (T7SS), offering potential therapeutic targets.
Area of Science:
- Microbiology
- Genomics
- Infectious Diseases
Background:
- Streptococcus intermedius (SI) infections are linked to severe outcomes, including prolonged hospitalization and reduced survival rates.
- The genetic basis of SI's role in brain abscess development and its evolutionary relationship with other Streptococcus anginosus group species remain poorly understood.
- Understanding SI's genomic landscape is crucial for developing effective treatments.
Purpose of the Study:
- To conduct a comprehensive whole-genome comparative analysis of SI isolates, focusing on virulence factors, genomic evolution, and the type seven secretion system (T7SS).
- To investigate the genetic mechanisms underlying SI pathogenicity, particularly in relation to brain abscess formation.
- To identify potential therapeutic targets within the SI genome.
Main Methods:
- Whole-genome comparative analysis of an SI brain abscess isolate (LAU_SINT) against other SI, Streptococcus constellatus, and Streptococcus anginosus genomes.
- Assessment of selective pressures on virulence factors, phage content, pan-genome evolution, and single-nucleotide polymorphism (SNP) analysis.
- Elucidation and comparative analysis of the type seven secretion system (T7SS) structure and genomic location.
Main Results:
- Identified conserved and abundant ily and nanA genes. Nisin resistance determinants were present in 47% of isolates.
- Genome analysis revealed no significant geo-patterns in pan-genome or SNP data. Two Streptococcus constellatus isolates were initially misidentified as SI.
- Characterized four proposed T7SS modules (I-IV) located on genomic islands, associated with metal ion-binding factors. This is the first report linking T7SS, nisin resistance, and metal ion binding in SI.
Conclusions:
- The study provides the first detailed characterization of the T7SS in SI, highlighting its association with nisin resistance and metal ion binding.
- Uncharacterized T7SS transmembrane proteins in SI represent promising avenues for future research and potential therapeutic development.
- Accurate identification of bacterial species is critical, as demonstrated by the misclassification of two isolates.
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