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Macrolide resistance phenotypes and mechanisms of resistance in Streptococcus pyogenes in La Rioja, Spain
A Portillo1, M Lantero, M J Gastañares
1Area de bioquímica y Biologia Molecular, Universidad de La Rioja, Logroño, Spain.
Abstract:
One hundred and thirty seven consecutive clinical Streptococcus pyogenes isolates were evaluated for macrolide-lincosamide-streptogramin resistance (MLS). Forty of these isolates were resistant to erythromycin (29.2%), 36 of them showed the new M resistance phenotype (erythromycin resistant and clindamycin susceptible) and four isolates had the MLS(B) resistance phenotype (erythromycin and clindamycin resistant). In all 36 isolates with the M resistance phenotype, the mef gene was identified by polymerase chain reaction (PCR). In two of the four S. pyogenes isolates with the MLS(B) phenotype, both ermB and ermTR genes were found; negative results were obtained with the other two isolates which might possess a new mechanism of high level resistance against erythromycin not previously described. In summary, a high rate of erythromycin resistance was found in S. pyogenes isolates and the active efflux pump mediated by the mef gene was the mechanism most frequently involved.
Insights
A high rate of erythromycin resistance was found in Streptococcus pyogenes clinical isolates. The mef gene, mediating an active efflux pump, was the most frequent resistance mechanism identified.
Area of Science:
- Microbiology
- Molecular Biology
- Antimicrobial Resistance
Background:
- Streptococcus pyogenes is a significant human pathogen.
- Macrolide-lincosamide-streptogramin (MLS) resistance is a growing concern in clinical settings.
- Understanding resistance mechanisms is crucial for effective treatment strategies.
Purpose of the Study:
- To investigate the prevalence of MLS resistance in clinical Streptococcus pyogenes isolates.
- To identify the genetic mechanisms underlying erythromycin resistance in these isolates.
Main Methods:
- Phenotypic characterization of MLS resistance in 137 S. pyogenes isolates.
- Molecular identification of resistance genes using polymerase chain reaction (PCR).
Main Results:
- Overall erythromycin resistance was 29.2% (40/137 isolates).
- The M resistance phenotype (erythromycin resistant, clindamycin susceptible) was observed in 36 isolates, with the mef gene identified in all.
- The MLS(B) phenotype (erythromycin and clindamycin resistant) was found in 4 isolates, with ermB and ermTR genes detected in two.
Conclusions:
- A high prevalence of erythromycin resistance exists in clinical S. pyogenes.
- The mef gene-mediated efflux pump is the predominant mechanism of resistance.
- Potential novel resistance mechanisms warrant further investigation.