Multiple-locus variable-number tandem repeat analysis for genotyping of erythromycin-resistant group B streptococci
Mahsa Ghamari1, Fereshteh Jabalameli1, Mohammad Emaneini1,2
1Department of Microbiology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
Background:
Group B Streptococcus (GBS or S. agalactiae) is an important pathogen causing severe invasive diseases in neonates, pregnant women, and adults with underlying medical conditions.
Methods:
To investigate the incidence of resistance to macrolide, lincosamide and streptogramin type B (MLSB) antibiotics, macrolide and tetracycline resistance determinants and genetic relationships, a total of 146 clinical isolates of GBS were collected from Tehran, Iran. The genetic relationships between erythromycin-resistant strains were determined by multilocus variable tandem repeat analysis (MLVA).
Results:
All isolates were susceptible to penicillin, vancomycin, linezolid, and quinupristin-dalfopristin, but were resistant to tetracycline (96.6%, 141/146), erythromycin (28.1%, 41/146) and clindamycin (16.4%, 24/146). Among the 41 erythromycin-resistant GBS (ERGBS), the most common antimicrobial resistance gene was tetM detected in 92.7% (38/41) of the isolates followed by ermTR and ermB found in 65.8% (27/41) and 29.3% (12/41) of isolates, respectively. Of the 41 ERGBS, 95% (39/41) exhibited the constitutive MLSB phenotype, 2.4% (1/41) displayed inducible MLSB and 2.4% (1/41) had M phenotype. The erm methylase genes were widely related to MLSB phenotype isolates, while the mefA gene was associated with M phenotype. MLVA analysis performed on the 41 ERGBS revealed that 34 MLVA types (MTs). MLVA analysis showed that infections due to ERGBS have been caused by a variety of genotypes, suggesting that ERGBS were clonally unrelated and dissemination of these isolates was not due to a clonal outbreak.
Conclusion:
Careful usage of macrolide antibiotics in therapy, continued surveillance of resistance rate and appropriate infection control measures can help to reduce spreading of resistance isolates.
Insights
Group B Streptococcus (GBS) shows high resistance to tetracycline and macrolide antibiotics. Multilocus variable tandem repeat analysis (MLVA) revealed diverse GBS genotypes, indicating no clonal outbreaks.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Group B Streptococcus (GBS or *S. agalactiae*) is a significant pathogen.
- GBS causes severe invasive diseases in neonates, pregnant women, and adults.
Purpose of the Study:
- Investigate GBS resistance to macrolide, lincosamide, and streptogramin B (MLSB) antibiotics.
- Determine macrolide and tetracycline resistance genes and genetic relationships among GBS isolates.
Main Methods:
- Collected 146 clinical GBS isolates from Tehran, Iran.
- Determined antimicrobial resistance profiles and resistance genes (e.g., *tetM*, *ermTR*, *ermB*, *mefA*).
- Utilized multilocus variable tandem repeat analysis (MLVA) for genetic typing of erythromycin-resistant GBS (ERGBS).
Main Results:
- High resistance rates observed for tetracycline (96.6%), erythromycin (28.1%), and clindamycin (16.4%).
- The *tetM* gene was most prevalent (92.7%) among ERGBS, followed by *ermTR* (65.8%) and *ermB* (29.3%).
- MLVA identified 34 distinct MLVA types among 41 ERGBS, indicating diverse genotypes and no clonal spread.
Conclusions:
- Prudent use of macrolide antibiotics is recommended.
- Continued surveillance of GBS resistance rates is crucial.
- Implementing appropriate infection control measures can mitigate the spread of resistant GBS strains.
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