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In vitro activity of telithromycin (HMR 3647) against Greek Streptococcus pyogenes and Streptococcus pneumoniae
S Ioannidou1, P T Tassios, L Zachariadou
1Department of Hygiene and Epidemiology, Medical School, Athens University, 115 27 Athens (Goudi), Greece.
Abstract:
The susceptibilities to macrolides and telithromycin of 161 Streptococcus pyogenes and 145 Streptococcus pyogenes strains, consecutively isolated from five Greek hospitals, were determined by Etest. Moreover, mechanisms of resistance to macrolides were phenotypically and genetically determined by double disk induction test and PCR, respectively. Of the S. pneumoniae and S. pyogenes isolates, 42.8% and 30.8%, respectively, were found to be resistant to erythromycin. Of the erythromycin-resistant S. pneumoniae and S. pyogenes isolates, 57.5% and 59.5%, respectively, displayed the M phenotype and harbored the mefA/E gene. Telithromycin was found to be more active than both erythromycin and clarithromycin against both species, with considerably lower MIC50 and MIC90 values.
Insights
This study assessed macrolide and telithromycin resistance in Streptococcus pneumoniae and Streptococcus pyogenes. Most resistant strains showed the M phenotype, driven by the mefA/E gene, with telithromycin proving most effective.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Streptococcus pneumoniae and Streptococcus pyogenes are significant human pathogens.
- Macrolide resistance in these bacteria is a growing public health concern.
- Understanding resistance mechanisms is crucial for effective treatment strategies.
Purpose of the Study:
- To determine the susceptibility of Streptococcus pneumoniae and Streptococcus pyogenes to macrolides and telithromycin.
- To investigate the mechanisms of macrolide resistance in these bacterial species.
- To compare the in vitro activity of telithromycin against erythromycin and clarithromycin.
Main Methods:
- Susceptibility testing using Etest for macrolides and telithromycin.
- Phenotypic determination of macrolide resistance mechanisms via double disk induction test.
- Genetic determination of resistance mechanisms using PCR to detect the mefA/E gene.
Main Results:
- High rates of erythromycin resistance were observed in both S. pneumoniae (42.8%) and S. pyogenes (30.8%).
- A majority of erythromycin-resistant isolates (57.5% of S. pneumoniae, 59.5% of S. pyogenes) exhibited the M phenotype and carried the mefA/E gene.
- Telithromycin demonstrated superior activity against both species compared to erythromycin and clarithromycin, indicated by lower MIC50 and MIC90 values.
Conclusions:
- The mefA/E gene and M phenotype are prevalent mechanisms of macrolide resistance in Greek isolates of S. pneumoniae and S. pyogenes.
- Telithromycin is a promising therapeutic option due to its potent activity against these resistant strains.
- Continued surveillance of antimicrobial resistance patterns is essential for guiding clinical practice.