Article in Japanese

Clinical evaluation of a rapid molecular test for the detection of Streptococcus pyogenes and the characteristics of molecular epidemiology for the isolates

Satoshi Iwata^{1）, 2）}, Kimiko Ubukata^{1）, 3）}, Miyuki Morozumi^1）, Masahiko Yamazaki^4）, Takashi Abe^5）, Toru Shibata^6）, Ryuta Yonezawa^7）, Shigeki Nakamura^1）, Keiko Mitamura^8）

In cases of suspected Group A Streptococcus （GAS） infection in children with pharyngitis and tonsillitis, it is important to identify the organism to decide whether antimicrobial treatment is appropriate. Recently, the ID NOWTM Strep A2 （ID NOW）, a rapid molecular test based on isothermal nucleic acid amplification, was approved in Japan and has been used in outpatient care. In this study, the sensitivity, specificity and total agreement of ID NOW versus throat culture were compared with those of antigen testing and real-time PCR. Additionally, the relationship between these results and the McIsaac score was investigated.
The sensitivity and specificity of ID NOW versus throat culture were 98.9% and 88.9% respectively. In contrast, the sensitivity and specificity of the antigen testing were 78.5% and 90.0%, while those of PCR were 100% and 95.0%, respectively. Notably, ID NOW showed superior sensitivity to antigen testing in suspected GAS cases with McIsaac scores of 1 to 3．A secondary analysis of the emm type for the isolates revealed a short-term shift in the prevalent types, with a significant increase in the highly pathogenic emm1 type, which specifically produces the Streptococcal Inhibitor of Complement-Mediated Lysis （SIC） protein.
In conclusion, highly sensitive and rapid molecular test is suitable for the appropriate use of antimicrobial agents and the prevention of GAS transmission.

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1）Department of Microbiology, Tokyo Medical University
2）Vaccine Development Research Center, Faculty of Life Sciences, Kumamoto University
3）Center for General Medicine education, Keio University School of Medicine
4）Zama Pediatric Clinic
5）Abe Pediatric Clinic
6）Futaba Pediatric Clinic
7）Matsuba Pediatrics Clinic
8）Eiju General Hospital

Key words	Group A Streptococcus，nucleic acid amplification，ID NOWTM Strep A2，sensitivity and specificity，emm typing
Received	October 13, 2024
Accepted	December 8, 2024

37 (1)：3─14,2025