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Updated: Oct 5, 2025
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
Predominance of ST8 and CC1/spa-t1784 methicillin-resistant Staphylococcus aureus isolates in Japan and their genomic
Kohei Ogura1, Daiki Kaji2, Masakazu Sasaki3
1Advanced Health Care Science Research Unit, Institute for Frontier Science Initiative, Kanazawa University, Kanazawa, Japan.
Objectives:
Methicillin-resistant Staphylococcus aureus (MRSA) has become a serious epidemiologic problem worldwide. In this study, we aimed to investigate recently isolated MRSA types and determine their characteristics.
Methods:
We collected 164 strains isolated from 13 hospitals located in Tokyo and surrounding prefectures. In addition to drug resistance tests, we sequenced whole genomes of the prevalent MRSA clones and analysed their genomic characteristics, such as drug resistance genes, virulence factor genes, and genome arrangements.
Results:
Multilocus sequencing typing showed that 51% of the SCCmecⅣ MRSA isolates belonged to clonal complex 1 (CC1). Staphylococcus protein A gene (spa) typing showed that 91% of these CC1 isolates could be categorised as t1784 type. These CC1/t1784 isolates possessed genes encoding erythromycin resistance protein, spectinomycin 9-adenylyltransferase, and staphylococcal enterotoxins (SEA, SEI, SEM), but not the pvl gene encoding Panton-Valentine leukocidin. Complete genomic analysis of nine CC1/t1784 isolates showed that they shared an intact phage, which carried no annotated virulence factor genes except for two encoding a hypothetical membrane protein and a teichoic acid biosynthesis protein. No significant genomic rearrangements were observed among the CC1/t1784 isolates.
Conclusion:
These data and previous reports indicate that this CC1/t1784 clone has been expanding rapidly in Japan without genomic changes.
Insights
A rapidly expanding Methicillin-resistant Staphylococcus aureus (MRSA) clone, CC1/t1784, is prevalent in Japan. This specific MRSA type shows drug resistance and specific toxin genes but lacks the pvl gene and significant genomic changes.
Area of Science:
- Microbiology
- Genomics
- Epidemiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant global health challenge.
- Understanding the characteristics of emerging MRSA strains is crucial for effective control strategies.
Purpose of the Study:
- To investigate and characterize recently isolated MRSA types in Japan.
- To determine the genomic features, including resistance and virulence genes, of prevalent MRSA clones.
Main Methods:
- Collected 164 MRSA strains from 13 hospitals in the Tokyo region.
- Performed drug resistance testing, whole-genome sequencing, multilocus sequence typing, and spa typing.
- Analyzed genomic characteristics, including resistance genes, virulence factors, and genome arrangements.
Main Results:
- The CC1/t1784 clone, characterized by SCCmec IV, represented 51% of MRSA isolates.
- These isolates possessed erythromycin and spectinomycin resistance genes, staphylococcal enterotoxins (SEA, SEI, SEM), but lacked the pvl gene.
- Whole-genome analysis revealed a shared intact phage with limited annotated virulence genes and no significant genomic rearrangements.
Conclusions:
- The CC1/t1784 MRSA clone is expanding rapidly in Japan.
- This clone exhibits specific genetic markers for drug resistance and toxin production without apparent genomic alterations.
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