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Updated: Jul 13, 2026
Multiplex PCR Assay for Typing of Staphylococcal Cassette Chromosome Mec Types I to V in Methicillin-resistant Staphylococcus aureus
Published on: September 5, 2013
[Genotypes of Staphylococcus aureus strains with methicillin resistant phenotype]
Myra S Wilson1, Carola L Otth, Gustavo S Medina
1Instituto de Microbiología Clínica, Universidad Austral de Chile, Valdivia, Chile. myrawilson@uach.cl
Background:
Methicillin resistant strains of Staphylococcus aureus (MRSA) are an important cause of nosocomial infections.
Aim:
To determine the genotypes of MRSA strains.
Material And Methods:
Fifty five strains of MRSA, isolated from patients hospitalized in Hospital Base Valdivia, were studied. The phenotype was determined through MicroScan in all strains and by minimum inhibitory concentration (MIC) in 41. The genotype of the strains was analyzed by a duplex polymerase chain reaction (PCR) of the mecA gene, amplifying eight hypervariable DNA regions associated to such gene.
Results:
According to MIC, 88% of strains had a pattern of resistance against multiple antimicrobial (penicillin, ampicillin, cephradine, gentamycin, ciprofloxacin, lincomycin and erythromycin). Vancomicin resistan strains were not detected. Only 53 strains (96%) had at least one of the eight hypervariable regions and were classified as MRSA. Genotypic patterns types 15 were the most commonly detected in 38% and 34% of strains, respectively. MicroScan erroneously classified five strains in an incorrect phenotype, according to results obtained with duplex PCR. MIC results did not differ from those of duplex PCR.
Conclusions:
Duplex- PCR is a useful tool to detect hyper variable regions associated to mecA gene.
Insights
Duplex PCR effectively identifies genetic markers in Methicillin-resistant Staphylococcus aureus (MRSA) strains, aiding in accurate diagnosis and understanding of antimicrobial resistance patterns.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Context:
- Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant threat as a cause of hospital-acquired infections.
- Accurate genotypic characterization of MRSA strains is crucial for effective infection control and treatment strategies.
Purpose:
- To determine the genotypes of MRSA strains.
- To evaluate the utility of duplex polymerase chain reaction (PCR) for identifying hypervariable regions associated with the mecA gene in MRSA.
Summary:
- Fifty-five MRSA strains were analyzed using phenotypic methods (MicroScan, MIC) and genotypic analysis (duplex PCR targeting the mecA gene).
- Duplex PCR identified specific genotypic patterns (types 1 and 5) in 96% of strains, correlating well with MIC results.
- MicroScan misclassified five strains, highlighting the diagnostic advantage of duplex PCR.
Impact:
- Duplex PCR is confirmed as a valuable tool for detecting hypervariable regions linked to the mecA gene in MRSA.
- This genotypic method enhances the accuracy of MRSA classification and aids in understanding antimicrobial resistance mechanisms.
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