Identifying Genetic Variations in emm 89 Streptococcus pyogenes Associated with Severe Invasive Infections

  1. Masayuki Ono
  2. Masaya Yamaguchi
  3. Daisuke Motooka
  4. Yujiro Hirose
  5. Kotaro Higashi
  6. Tomoko Sumitomo
  7. Tohru Miyoshi-Akiyama
  8. Rumi Okuno
  9. Takahiro Yamaguchi
  10. Ryuji Kawahara
  11. Hitoshi Otsuka
  12. Noriko Nakanishi
  13. Yu Kazawa
  14. Chikara Nakagawa
  15. Ryo Yamaguchi
  16. Hiroo Sakai
  17. Yuko Matsumoto
  18. Tadayoshi Ikebe
  19. Shigetada Kawabata

  • Curated by eLife

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    eLife Assessment

    This study provides a valuable and timely analysis of invasive and non-invasive Streptococcus pyogenes emm89 isolates, which have become a dominant serotype in the past decade. Using genome sequencing of 311 strains from Japan and comparing them with 666 global strains, the authors present compelling evidence in support of the identification of genetic factors linked to the invasive phenotype of emm89. The findings are both theoretically and practically significant in medical microbiology.

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Abstract

Streptococcus pyogenes causes mild human infections as well as life-threatening invasive diseases. Since the mutations known to enhance virulence to date account for only half of the severe invasive infections, additional mechanisms/mutations need to be identified. Here, we conducted a genome-wide association study of emm 89 S. pyogenes strains to comprehensively identify pathology-related bacterial genetic factors (SNPs, indels, genes, or k-mers). Japanese (n=311) and global (n=666) cohort studies of strains isolated from invasive or non-invasive infections revealed 17 and 1,075 SNPs/indels and 2 and 169 genes, respectively, that displayed associations with invasiveness. We validated one of them, a non-invasiveness-related point mutation, fhuB T218C, by structure predictions and introducing it into a severe invasive strain and confirmed that the mutant showed slower growth in human blood. Thus, we report novel mechanisms that convert emm 89 S. pyogenes to an invasive phenotype and a platform for establishing novel treatments and prevention strategies.

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  1. Version published to 10.1101/2024.07.02.601674v2 on bioRxiv
  2. Version published to 10.7554/elife.101938.1 on eLife
  3. Version published to 10.7554/elife.101938 on eLife
  4. eLife

    eLife Assessment

    This study provides a valuable and timely analysis of invasive and non-invasive Streptococcus pyogenes emm89 isolates, which have become a dominant serotype in the past decade. Using genome sequencing of 311 strains from Japan and comparing them with 666 global strains, the authors present compelling evidence in support of the identification of genetic factors linked to the invasive phenotype of emm89. The findings are both theoretically and practically significant in medical microbiology.

  5. eLife

    Reviewer #1 (Public review):

    Summary:

    In this study, the authors sequenced emm89 serotype genomes of clinical isolates from patients in Japan, where the number of invasive Group A Streptococcus (GAS), especially those of the emm89 serotype, has drastically increased over the past 10-15 years. The sequences from this cohort were compared against a large collection of publicly available global isolates, yielding a total of almost 1000 genomes in the analysis. Because the researchers focused on the emm89 serotype, they could construct a common core genome, with subsequent ability to analyze genomic differences in accessory genes and intergenic regions that contributed to the invasive phenotype using multiple types of GWAS analysis (SNP, k-mer). Their analysis demonstrates some mutations responsible for invasiveness are specific to the Japanese strains, and that multiple independent virulence factors can contribute to invasiveness. None of the invasive phenotypes were correlated with new gene acquisition. Together, the data support that synergy between bacterial survival and upregulation of virulence factors contributes to the development of severe infection.

    Strengths:

    • The authors verify their analysis by confirming that covS is one of the more frequently mutated genes in invasive strains of GAS, as has been shown in other publications.

    • A mutation in one of the SNPs attributed to invasiveness (SNP fhuB) was introduced into an invasive strain. The authors demonstrate that this mutant strain survives less well in human blood. Therefore, the authors have experimental data to support their claims that their analysis uncovered a new mutation/SNP that contributed to invasiveness.

    Weaknesses:

    • It would be helpful for the authors to highlight why their technique (large scale analysis of one emm type) can yield more information than a typical GWAS analysis of invasive vs. non-invasive strains. Are SNPs easier to identify using a large-scale core genome? Is it more likely evolutionarily to find mutations in non-coding regions as opposed to the core genome and accessory genes, and this is what this technique allows? Did the analysis yield unexpected genes or new genes that had not been previously identified in other GWAS analyses? These points may need to be made more apparent in the results and deserve some thought in the discussion section.

    • The Alpha-fold data does not demonstrate why the mutations the authors identified could contribute to the invasive phenotype. It would be helpful to show an overlay of the predicted structures containing the different SNPs to demonstrate the potential structural differences that can occur due to the SNP. This would make the data more convincing that the SNP has a potential impact on the function of the protein. Similarly, the authors discuss modification of the hydrophobicity of the side chain in the ferrichrome transporter (lines 317-318) due to a SNP, but this is not immediately obvious in the figure (Fig. 5).

  6. eLife

    Reviewer #2 (Public review):

    Summary:

    In this manuscript, the authors aim to identify genetic determinants associated with the invasion profile of Streptococcus pyogenes strains of the emm89 type, which has been increasingly linked to invasive infections. The study leverages both in-house sequenced genomes and publicly available genomic data. Several GWAS approaches are applied to these datasets, leading to the identification of potential genetic targets. For these targets, the authors conduct additional analyses, including three-dimensional structural modeling of the encoded proteins, as well as the development of mutant strains. The functional impact of these mutations is further explored through transcriptomic comparisons between the mutants and wild-type strains

    Strengths:

    The strengths of this manuscript include the large amount of data analyzed and the various methodologies applied. The identification of CovS, a gene known to influence the invasion profile, as a significant variation further validates the methodology employed in this study. Then, the gene fhuD is an intriguing target, identified through both bioinformatics and wet lab approaches.

    Weaknesses:

    I do not identify any additional weaknesses in the manuscript, beyond those already acknowledged by the authors themselves.

  7. Version published to 10.1101/2024.07.02.601674v1 on bioRxiv