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Published on: September 5, 2013
Emergence of ST3390: A Novel Apigmented MRSA Clone From the CC5 Lineage
Emily A Felton1,2, Mary-Elizabeth Jobson1,2, Nathanial J Torres1,2
1Department of Molecular Biosciences, University of South Florida, Tampa, Florida, USA.
Background:
One of the most successful and widely-distributed hospital-associated lineages of MRSA is clonal complex 5 (CC5). These strains are known for widespread antibiotic resistance but less severe disease than CA-MRSA counterparts. Recently, CC5 descendant lineages have appeared globally with hypervirulent properties. Herein, we identify and characterize a rare and novel CC5 MRSA sequence type, ST3390.
Methods:
We used whole genome sequencing, alongside phenotypic characterizations, genetic complementation, blood viability- and neutrophil-killing assays, and a murine model of sepsis to study the pathogenic capabilities of ST3390 strains.
Results:
To date, there have only been 65 recorded instances of infection caused by ST3390 globally, with 36 of those occurring in Tampa (TPA-ST3390). Genomic analysis of strains identified numerous spa-types, with a t010 cluster found only in our strains. Exploration of AMR genes detected the presence of unique hybrid SCCmec types, with ∼90% of Tampa strains possessing components of SCCmecIa, SCCmecIIa, and/or SCCmecVIII. Phenotypically, all ST3390 strains lack the staphyloxanthin pigment, which is mediated by a conserved 6aa in frame deletion within the staphyloxanthin biosynthesis protein CrtN. TPA-ST3390 strains display high levels of cytotoxicity towards human neutrophils compared with other CC5 lineages and are also virulent in animal models of infection.
Conclusions:
This is the first study to characterize the pathogenicity and genomic architecture of the rare MRSA lineage ST3390. Our work provides a deeper understanding of the clonal expansion of CC5, and the wider diversification of Staphylococcus aureus isolates within patient populations.
Insights
A rare Methicillin-resistant Staphylococcus aureus (MRSA) lineage, ST3390, has been identified. This CC5 MRSA strain exhibits hypervirulence, increased cytotoxicity, and unique genetic traits, expanding our understanding of S. aureus diversification.
Area of Science:
- Microbiology
- Genomics
- Infectious Diseases
Background:
- Clonal complex 5 (CC5) is a prevalent hospital-associated MRSA lineage known for antibiotic resistance.
- Emerging CC5 descendant lineages display hypervirulent properties globally.
- This study identifies and characterizes a novel and rare CC5 MRSA sequence type, ST3390.
Purpose of the Study:
- To identify and characterize the rare MRSA lineage ST3390.
- To investigate the pathogenic capabilities and genomic architecture of ST3390.
- To understand the diversification of S. aureus within patient populations.
Main Methods:
- Whole genome sequencing
- Phenotypic characterizations
- In vitro assays (blood viability, neutrophil-killing) and in vivo murine model of sepsis.
Main Results:
- ST3390 is a rare MRSA lineage with 65 global cases, predominantly in Tampa (TPA-ST3390).
- Genomic analysis revealed unique spa-types and hybrid SCCmec types in TPA-ST3390 strains.
- ST3390 strains exhibit high neutrophil cytotoxicity and virulence in murine sepsis models, lacking staphyloxanthin pigment.
Conclusions:
- This is the first characterization of the pathogenicity and genomic architecture of the rare MRSA lineage ST3390.
- The findings deepen the understanding of CC5 clonal expansion and S. aureus diversification.
- ST3390 represents a significant, hypervirulent MRSA lineage with unique genetic and phenotypic traits.
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