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Genotyping of Staphylococcus aureus by Ribosomal Spacer PCR RS-PCR
Published on: November 4, 2016
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Finding of Agr Phase Variants in Staphylococcus aureus
Vishal Gor1, Aya J Takemura2, Masami Nishitani3
1Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Japan.
Mbio
|August 8, 2019
Summary
Some Staphylococcus aureus strains with inactivated Agr systems can regain function through reversion. These Agr-revertant strains may act as a survival strategy against host immune responses during infection.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Molecular Biology
Background:
- Staphylococcus aureus utilizes virulence factors for host invasion and survival.
- The accessory gene regulator (Agr) system controls virulence factor expression.
- Many clinical S. aureus isolates have inactivated Agr systems, previously considered irreversible.
Purpose of the Study:
- To investigate the potential for Agr-negative Staphylococcus aureus mutants to revert to Agr activity.
- To identify the genetic mechanisms underlying Agr reversion in S. aureus.
Main Methods:
- Serial passage of Agr-negative S. aureus strains.
- Screening for phenotypic reversion of hemolysis.
- DNA sequencing to identify genetic mutations responsible for reversion.
- Testing Agr revertant activation upon phagocytosis.
Main Results:
- A fraction of Agr-negative S. aureus strains can revert Agr activity.
- Two distinct mutational events were identified: duplication-inversion and poly(A) tract alteration.
- A clinical MRSA isolate generated Agr-revertant colonies via poly(A) tract changes.
- Agr revertants activate their Agr system upon phagocytosis.
Conclusions:
- Agr-negative S. aureus strains can exhibit phase variation, reverting to Agr activity.
- Reversion mechanisms include genetic duplication/inversion and poly(A) tract alterations.
- Agr revertants may represent a cryptic survival strategy against host immune stress.
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