2021 Fiscal Year Research-status Report
Temperature-driven regulation system of hypermucoviscosity in carbapenem-resistant Klebsiella pneumoniae
| Project/Area Number |
21K16947
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| Research Institution | Hiroshima University |
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Principal Investigator |
レ グエントラミ 広島大学, 医系科学研究科(歯), 助教 (20897904)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | Klebsiella pneumoniae / hypermucoviscous / hypervirulent / multidrug resistance / string test |
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| Outline of Annual Research Achievements |
Klebsiella pneumoniae (Kp) has emerged as a global life-threatening pathogen owing to its multidrug resistance and hypervirulence phenotype. Hypermucoviscosity (HMV) is a phenotype commonly associated with hypervirulence of Kp, which is usually regulated by rmpA or rmpA2 (regulators of the mucoid phenotype). My study has found that temperature was important in HMV phenotype of Kp, and the impact of temperature on HMV was not uniform among strains. I investigated the HMV phenotype at 37°C and room temperature in 170 clinically isolated hypermucoviscous Kp strains in Japan and analyzed the association between the HMV phenotype, virulence genes, and antimicrobial resistance (AMR) genes. String length distribution at different temperatures was correlated with the genomic population of Kp. The strains carrying rmpA/rmpA2 frequently showed the HMV phenotype at 37°C, while the strains negative for these genes tended to show the HMV phenotype at room temperature. Hypervirulent Kp clusters carried rmpA/rmpA2 without extended-spectrum beta-lactamases (ESBL)/carbapenemases, produced higher string lengths at 37 °C than at room temperature, and were mostly isolated from the respiratory tract. Other HMV strains showed distinct characteristics of not carrying rmpA/rmpA2 but were positive for ESBL/carbapenemases, with a higher string length at room temperature than at 37°C, and were frequently isolated from bloodstream infections.
My first manuscript of this topic has been accepted in Microbial Genomics on April 14th and is going to be published soon.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
I have finished the first stage of my research proposal with an accepted paper in Microbial Genomics entitle "Genomic epidemiology and temperature dependency of hypermucoviscous Klebsiella pneumoniae in Japan". The paper is currently under production and is expected to be published in May or June.
At this moment, I am proceeding the next stage with the focus on the molecular mechanisms of temperature-driven hypermucoviscosity. Hopefully we will produce some more papers in the coming year.
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| Strategy for Future Research Activity |
In the next stage, the isolates with medium/high-HMV phenotype and negative for rmpA and rmpA2 genes will be selected for investigation of novel gene(s) responsible for hypermucoviscosity.
Isolates with medium/high-HMV phenotype and negative for rmpA and rmpA2 genes will be selected for investigation of novel gene(s) responsible for hypermucoviscosity.
(1) RNA sequencing. Predicted genes responsible for the HMV phenotype will be recognized using the RNA sequencing method.
(2) Construction of bacterial mutants and complementation strains. Deletion mutants of predicted HMV genes will be constructed to evaluate the alteration in HMV phenotype, then complementation strains will be created to confirm the restoration of the HMV phenotype in the deletion mutants.
(3) Virulence assay: neutrophil killing assay, murine pneumonia model. Neutrophil killing assay and murine pneumonia model assay will be performed on wild type strains, deletion mutants and complementation strains to observe the role of HMV phenotype in virulence of these strains.
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