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Updated: Mar 14, 2026
Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
Molecular epidemiology, antimicrobial susceptibility, and characterization of macrolide-resistant Streptococcus
Yuhei Tanaka1, Kenji Gotoh1, Mariko Teramachi1
1Department of Pediatrics and Child Health, Kurume University School of Medicine, Kurume, Japan.
Abstract:
Here we report the molecular epidemiology of macrolide-resistant Streptococcus pyogenes (group A streptococci, GAS) isolated from children with pharyngotonsillitis between 2011 and 2013 in Japan. In 299 isolates, 124 (41.5%) isolates were macrolide-resistant. We characterized the isolates by emm typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE). Of 299 isolates, 124 (41.5%) were macrolide-resistant isolates, 76 (61.3%) possessed mefA and 46 (37.1%) possessed ermB. All 76 isolates with mefA possessed msrD. There were no isolates possessed ermTR in this study. Eight emm/MLST types were observed. The predominant type was emm1/ST28 (57 isolates, 46.0%), which possessed the mefA/msrD complex, presenting as the M phenotype. The second most predominant type was emm12/ST467, which possessed ermB, presenting as the cMLSB phenotype. Of the cMLSB phenotype isolates, types emm28/ST52 and emm12/ST36 had multiple genetic backgrounds. We found high proportions of macrolide-resistant GAS in the southwestern areas of Japan.
Insights
Macrolide resistance in Streptococcus pyogenes (GAS) is common in Japanese children, with over 40% of isolates resistant. The mefA gene was the most frequent resistance mechanism identified in these macrolide-resistant GAS strains.
Area of Science:
- Microbiology
- Epidemiology
- Molecular Biology
Background:
- Streptococcus pyogenes (group A streptococci, GAS) causes pharyngotonsillitis in children.
- Macrolide resistance in GAS is a growing public health concern.
- Understanding the molecular epidemiology of resistant strains is crucial for effective treatment.
Purpose of the Study:
- To investigate the molecular epidemiology of macrolide-resistant GAS in children with pharyngotonsillitis in Japan.
- To characterize the genetic basis and prevalence of macrolide resistance mechanisms.
- To identify dominant GAS strains and their resistance profiles.
Main Methods:
- Isolation and characterization of 299 GAS isolates from children with pharyngotonsillitis (2011-2013).
- Molecular typing including emm typing, multilocus sequence typing (MLST), and pulsed-field gel electrophoresis (PFGE).
- Detection of macrolide resistance genes (mefA, ermB, msrD, ermTR).
Main Results:
- 124 out of 299 (41.5%) GAS isolates were macrolide-resistant.
- The mefA gene (with msrD) was present in 76 isolates (M phenotype), and ermB was present in 46 isolates (cMLSB phenotype).
- emm1/ST28 (M phenotype) and emm12/ST467 (cMLSB phenotype) were the predominant types, with high proportions of macrolide-resistant GAS found in southwestern Japan.
Conclusions:
- Macrolide resistance is highly prevalent in pediatric GAS isolates in Japan.
- The mefA/msrD complex and ermB are the primary genetic determinants of macrolide resistance.
- Geographical variations in resistance and specific emm/MLST types highlight the need for ongoing surveillance.
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