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Macrolide-lincosamide-streptogramin B resistant phenotypes and genotypes for methicillin-resistant Staphylococcus
H Cem Gul1, Abdullah Kilic, Aylin Uskudar Guclu
1Department of Infectious Diseases, Gulhane Military Medical Academy and School of Medicine, 06018 Etlik, Ankara, Turkey.
Abstract:
Methicillin-resistant Staphylococcus aureus (MRSA) strains with inducible macrolide-lincosamide-streptogramin B (iMLS(B)) resistance phenotype may lead to clinical failure during clindamycin (CLI) therapy. The aim of this study was to determine the incidence of MLS(B) phenotypes by using D-test method and genotypes by using multiplex real-time PCR method in MRSA strains. A total of 265 MRSA strains were obtained from clinical samples from hospitalized and outpatients. Of the MRSA isolates, 225 (84.9%) were resistant to erythromycin (ERT), and 170 (64.1%) to CLI. Among the 225 ERT-resistant MRSA strains, the constitutive MLS(B) (cMLS(B)) rate was found in 49.3%, iMLS(B) in 39.1% and the M phenotype in 11.5%. Overall, ermA, ermC, ermA+ermC, msrA, ermC+msrA, and ermA+ermC+msrA genes were detected in 85 (37.7%), 60 (26.6%), 42 (18.6%), 26 (11.5%), 11 (4.8%), and 1 (0.4%) isolates, respectively. Most prevalent resistance determinant in MRSA strains was ermA, which was detected in 37.7% of the isolates. The 26 MRSA strains with M phenotype harboured only msrA gene. In conclusion, due to aware of the potential of CLI treatment failure, D-test should be performed and reported in MRSA strains in clinical laboratories. The multiplex real-time PCR method is easy to perform, fast and reliable method for the detection of MLS(B) resistance genotypes.
Insights
Inducible macrolide-lincosamide-streptogramin B (iMLS(B)) resistance in MRSA can cause clindamycin treatment failure. D-test and PCR are vital for detecting resistance genotypes in clinical labs.
Area of Science:
- Medical Microbiology
- Antimicrobial Resistance
- Molecular Diagnostics
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat in healthcare settings.
- Inducible macrolide-lincosamide-streptogramin B (iMLS(B)) resistance in MRSA can lead to treatment failure with clindamycin (CLI).
- Accurate detection of resistance mechanisms is crucial for effective antibiotic selection.
Purpose of the Study:
- To determine the incidence of MLS(B) phenotypes in MRSA using the D-test.
- To identify MLS(B) resistance genotypes in MRSA strains via multiplex real-time PCR.
- To assess the correlation between phenotypic and genotypic resistance patterns.
Main Methods:
- Phenotypic detection of MLS(B) resistance using the D-test.
- Genotypic detection of resistance genes (ermA, ermC, msrA) using multiplex real-time PCR.
- Analysis of 265 MRSA strains isolated from clinical samples.
Main Results:
- High rates of resistance to erythromycin (84.9%) and clindamycin (64.1%) were observed.
- Prevalence of constitutive MLS(B) (cMLS(B)), inducible MLS(B) (iMLS(B)), and M phenotypes were 49.3%, 39.1%, and 11.5% respectively among erythromycin-resistant strains.
- The ermA gene was the most prevalent resistance determinant (37.7%), followed by ermC (26.6%).
Conclusions:
- The D-test is essential for identifying inducible MLS(B) resistance, predicting potential clindamycin treatment failure in MRSA.
- Multiplex real-time PCR offers a rapid, reliable method for detecting MLS(B) resistance genotypes.
- Clinical laboratories should implement both D-test and molecular methods for comprehensive MRSA resistance profiling.
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