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Molecular epidemiology of macrolide resistant Group A streptococci from Puducherry, India
Tintu Abraham1, Sujatha Sistla2
1Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India. tintu75@gmail.com.
Introduction:
In penicillin allergic patients, macrolides are the most commonly used antibiotics for treating streptococcal infections, irrespective of the higher resistance rates. The objective of this study was to evaluate the comparative prevalence, phenotypes, and genetic determinants of macrolide resistance and associated emm types among different clinical isolates of Streptococcus pyogenes.
Methodology:
A total of 173 Streptococcus pyogenes isolates were examined for macrolide resistance phenotype by double-disc test, resistance determinants by multiplex PCR and emm genotyping.
Results:
Erythromycin resistance was found in 51.4% of isolates, with MIC90 ≥ 256 µg/mL Inducible phenotype was commonly found (iMLS, 67.4%) followed by the M phenotype (32.5%). Among these isolates, 65.1% harboured ermB and 32.5% mefA as sole macrolide resistance gene, whereas presence of both, ermB plus mefA was observed in 2.2% cases. The most common types among resistant strains were emm63 (11.2%), emm44 (6.7%), emm42 (5.6%), and emm75.3, emm82, emm85, emm92, emm111.1 (4.4% each). Statistically significant association was observed between emm63, emm44 and erythromycin resistance (p ≤ 0.05). Association of these emm types and macrolide resistance have not been reported earlier.
Conclusion:
Higher macrolide resistance in this study can be attributed to overuse and misuse of this antibiotic. These findings indicate that macrolides should not be empirically used for treating severe streptococcal infections.
Insights
Macrolide resistance in Streptococcus pyogenes is high, often linked to ermB and mefA genes. Avoid empirical macrolide use for severe infections due to resistance.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Macrolides are common antibiotics for penicillin-allergic patients with streptococcal infections.
- High macrolide resistance rates are a growing concern in Streptococcus pyogenes treatment.
Purpose of the Study:
- To evaluate macrolide resistance prevalence, phenotypes, and genetic determinants in Streptococcus pyogenes.
- To identify associations between specific emm types and macrolide resistance.
Main Methods:
- 173 Streptococcus pyogenes isolates were analyzed.
- Macrolide resistance phenotype determined by double-disc test.
- Resistance genes (ermB, mefA) and emm types identified using multiplex PCR and genotyping.
Main Results:
- 51.4% of isolates showed erythromycin resistance.
- Inducible macrolide resistance (iMLS) was prevalent (67.4%).
- ermB (65.1%) and mefA (32.5%) were common resistance genes; emm63 and emm44 showed significant association with resistance.
Conclusions:
- High macrolide resistance is linked to antibiotic overuse/misuse.
- Empirical use of macrolides for severe streptococcal infections is not recommended.
- Novel associations between emm types and macrolide resistance were identified.
