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[Streptococcus pyogenes: in vitro susceptibility to several antimicrobials in two date periods]
M S Giglio1, M Robles, M L Rioseco
1Departamento de Microbiología, Facultad de Medicina, Universidad de Chile (Campus Occidente), Santiago de Chile.
Background:
The frequency of Streptococcus pyogenes infections with deep tissue invasion and toxic shock syndrome has increased in the last decade throughout the world.
Aim:
To compare antimicrobial susceptibility of S. pyogenes strains isolated during 1986 and during 1994-95.
Material And Method:
Eighty two S. pyogenes strains isolated in 1986 and 67 strains isolated in 1994-95, were studied. MIC 50 and 90 were determined by and agar dilution method for penicillin, ampicillin, cefazolin, cefuroxime, erythromycin, roxithromycin and miocamycin.
Results:
Eighty eight strains came from skin of soft tissues, 19 from surgical wounds, 18 from invasive infections, 15 from pharyngeal swabs and 9 from other locations. All strains were susceptible to penicillin, ampicillin, cefazolin, cefuroxime, roxithromycin and miocamycin. Ninety nine percent of strains were susceptible to erythromycin. Strains isolated in 1995-95 had a higher MIC 50 and 90 for erythromycin than those isolated in 1986.
Conclusions:
The changes in susceptibility to erythromycin of recently isolated strains could be due to the widespread use of macrolides in Chile.
Insights
Antimicrobial susceptibility testing of Streptococcus pyogenes strains revealed that while most remained susceptible to common antibiotics, a concerning increase in erythromycin resistance was observed in later isolates. This trend may be linked to macrolide usage.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- The incidence of severe Streptococcus pyogenes infections, including deep tissue invasion and toxic shock syndrome, has globally escalated.
- This rise necessitates ongoing surveillance of bacterial susceptibility patterns.
Purpose of the Study:
- To evaluate and compare the antimicrobial susceptibility profiles of Streptococcus pyogenes strains.
- Specifically, to compare strains isolated in 1986 with those from 1994-1995.
Main Methods:
- Microbiological analysis of 82 Streptococcus pyogenes strains from 1986 and 67 strains from 1994-1995.
- Determination of Minimum Inhibitory Concentrations (MIC50 and MIC90) using agar dilution for key antibiotics: penicillin, ampicillin, cefazolin, cefuroxime, erythromycin, roxithromycin, and miocamycin.
Main Results:
- All tested strains demonstrated susceptibility to penicillin, ampicillin, cefazolin, cefuroxime, roxithromycin, and miocamycin.
- Ninety-nine percent of strains were susceptible to erythromycin.
- Strains isolated in 1994-1995 exhibited higher MIC50 and MIC90 values for erythromycin compared to strains from 1986, indicating reduced susceptibility.
Conclusions:
- Emerging resistance to erythromycin in recent Streptococcus pyogenes isolates is a significant finding.
- This observed change in susceptibility is potentially associated with the increased utilization of macrolide antibiotics in Chile.