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Characterization of Penicillin-Non-Susceptible, Multidrug-Resistant Streptococcus agalactiae Using Whole-Genome
Junghun Park1,2, Min-Kyung So3, Yu-Hee Kim2,4
1Ewha Medical Research Institute, Ewha Womans University College of Medicine, Seoul, Korea.
Current Microbiology
|June 24, 2025
Summary
Multidrug-resistant Streptococcus agalactiae (group B Streptococcus, GBS) strains show resistance to penicillin and other antibiotics. This study characterized four such clinical isolates, revealing key genetic mutations driving resistance and highlighting the need for ongoing surveillance.
Area of Science:
- Microbiology
- Genetics
- Infectious Diseases
Background:
- Streptococcus agalactiae (group B Streptococcus, GBS) is a significant pathogen causing severe infections in neonates and adults.
- Increasing multidrug resistance (MDR) in GBS, including penicillin non-susceptibility, poses a therapeutic challenge.
- Limited molecular genetic data exists for penicillin-non-susceptible GBS isolates.
Purpose of the Study:
- To characterize the resistance profiles and molecular epidemiology of penicillin-non-susceptible, MDR GBS clinical isolates.
- To identify genetic determinants associated with resistance in these GBS strains.
- To review clinical data associated with patients harboring these resistant GBS isolates.
Main Methods:
- Antimicrobial susceptibility testing using VITEK2, MicroScan, broth microdilution, and Etest.
- Whole-genome sequencing (Illumina MiSeq) and analysis of resistance-related genes (pbp, ciaH, rpo, quinolone resistance determinants).
- Review of clinical data for patients with GBS infections.
Main Results:
- Four GBS isolates displayed penicillin non-susceptibility (MIC 0.25 μg/mL) and MDR phenotypes, resistant to levofloxacin, erythromycin, clindamycin, and tetracycline.
- Borderline susceptibility observed for cefotaxime and ceftriaxone.
- Identified amino acid substitutions in penicillin-binding proteins (pbp), CiaH, RpoD, GyrA, and ParC linked to resistance.
- All isolates harbored erm(B), mre(A), and tet(M) resistance genes.
Conclusions:
- The emergence of penicillin-non-susceptible, MDR GBS, though rare, necessitates continuous surveillance.
- Understanding the genetic basis of resistance is crucial for developing effective treatment and prevention strategies.
- Further research is required to address the growing challenge of GBS antimicrobial resistance.
