Multiple-locus variable-number tandem-repeat assay analysis of methicillin-resistant Staphylococcus aureus strains

Area of Science:

• Microbiology
• Molecular Typing
• Infectious Diseases

Background:

• Pulsed-field gel electrophoresis (PFGE) is a standard method for typing Staphylococcus aureus.
• There is a need for simpler, more rapid molecular typing methods for S. aureus.
• Multiple-locus variable-number tandem-repeat analysis (MLVA) is a potential alternative.

Purpose of the Study:

• To evaluate if MLVA can predict PFGE types (USA types) of S. aureus.
• To assess MLVA as a replacement for PFGE for S. aureus strain typing.
• To determine the discriminatory power of MLVA for S. aureus.

Main Methods:

• Tested 103 S. aureus isolates from 13 lineages using both PFGE and MLVA.
• MLVA employed rapid DNA extraction and PCR for specific genetic markers.
• PFGE followed standard CDC protocols with SmaI digestion and analysis.

Main Results:

• Both MLVA and PFGE successfully typed all isolates with high reproducibility for MLVA.
• MLVA generated more types (28-45) than PFGE (13 types, 42 subtypes) depending on analysis.
• MLVA differentiated outbreak strains (USA300-0114) but did not distinguish community from healthcare MRSA lineages.

Conclusions:

• MLVA is a reproducible and potentially faster method for S. aureus typing.
• MLVA offers higher discriminatory power than PFGE for certain strain types.
• Further research is needed to explore MLVA's full epidemiologic value.