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Updated: Dec 25, 2025
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Epidemiology of methicillin-resistant Staphylococcus aureus in a Japanese neonatal intensive care unit
Atsushi Tsujiwaki1, Ken Hisata1, Yudai Tohyama1
1Department of Pediatrics and Adolescent Medicine, Juntendo University Graduate School of Medicine, Tokyo, Japan.
Background:
There have been few reports on the genetic structure of the current population of methicillin-resistant Staphylococcus aureus (MRSA) from neonatal intensive care units (NICUs) in Japan. In the present study we conducted a molecular epidemiological analysis based on whole genome sequencing against MRSA strains in a Japanese NICU.
Methods:
We performed genotyping by whole genome sequencing, polymerase chain reaction-based typing of Staphylococcal cassette chromosome mec (SCCmec) and polymerase chain reaction-based open-reading frame typing against 57 MRSA strains from fecal or nasal specimens from NICU patients in Juntendo University Shizuoka Hospital in 2013-2014.
Results:
Forty-nine MRSA strains (86.0%) exhibited a clonal complex (CC) 1, and were divided into three sequence types (STs): ST2725 (n = 25), ST2764 (n = 21), and ST1 (n = 3). All CC1 MRSA strains had SCCmec IVa, and were resistant to new quinolones, which are limited in pediatric use, suggesting that these strains were derived from adult MRSA clones. Single nucleotide polymorphism differences of both ≤10 and >100 nucleotides were observed by pairwise, single nucleotide polymorphism analysis among ST2725 and ST2764 MRSA strains, respectively. Seven ST8 MRSA strains (12.2%) were isolated, and no strain exhibiting the Japanese hospital-associated MRSA genotype (ST5/SCCmec II) was isolated in this study.
Conclusions:
Our molecular epidemiological analysis suggested that ST2725 and ST2764 MRSA strains had genetic diversity that could not be explained only by a recent transmission event in the NICU. These MRSA clones might be disseminated in other Japanese hospital facilities as new endemic clones. Our results are expected to contribute to the improvement of infection control measures of MRSA in NICUs.
Insights
New methicillin-resistant Staphylococcus aureus (MRSA) clones, ST2725 and ST2764, show genetic diversity in Japanese NICUs. These strains may become new endemic clones, impacting infection control measures.
Area of Science:
- Medical Microbiology
- Genomics
- Epidemiology
Background:
- Limited data exists on the genetic makeup of methicillin-resistant Staphylococcus aureus (MRSA) in Japanese neonatal intensive care units (NICUs).
- This study addresses the need for molecular epidemiological analysis of MRSA strains within a Japanese NICU setting.
Purpose of the Study:
- To investigate the genetic structure and molecular epidemiology of MRSA strains isolated from a Japanese NICU.
- To identify dominant MRSA clones and their genetic characteristics in this specific healthcare environment.
Main Methods:
- Whole genome sequencing was performed on 57 MRSA strains from fecal or nasal specimens collected between 2013-2014.
- Genotyping included Staphylococcal cassette chromosome mec (SCCmec) typing and open-reading frame typing.
Main Results:
- The majority of MRSA strains (86.0%) belonged to clonal complex 1, specifically ST2725 (n=25), ST2764 (n=21), and ST1 (n=3), all possessing SCCmec IVa.
- These CC1 strains showed resistance to new quinolones, suggesting adult clone origins. ST2725 and ST2764 exhibited significant genetic diversity.
- Seven ST8 MRSA strains (12.2%) were identified, while the typical Japanese hospital-associated MRSA genotype (ST5/SCCmec II) was absent.
Conclusions:
- The genetic diversity observed in ST2725 and ST2764 MRSA strains suggests origins beyond simple recent transmission within the NICU.
- These MRSA clones may represent emerging endemic strains with potential for wider dissemination in Japanese hospitals.
- Findings are crucial for enhancing MRSA infection control strategies in NICUs.
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