Effects of ceftobiprole and oxacillin on mecA expression in methicillin-resistant Staphylococcus aureus clinical...

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.
• The mecA gene is crucial for MRSA's resistance to beta-lactam antibiotics.
• Understanding mecA induction is vital for developing effective treatment strategies.

Purpose of the Study:

• To investigate the induction of the mecA gene by ceftobiprole and oxacillin in clinical MRSA isolates.
• To determine the correlation between mecA induction levels and antibiotic minimum inhibitory concentrations (MICs).
• To explore the relationship between mecA induction and Staphylococcal Cassette Chromosome mec (SCCmec) types.

Main Methods:

• Studied 18 clinical MRSA isolates with diverse SCCmec cassettes.
• Quantified mecA gene induction using reverse transcriptase PCR (RT-PCR).
• Determined MICs for ceftobiprole and oxacillin.

Main Results:

• mecA induction varied significantly (3-65 fold for ceftobiprole, 2-69 fold for oxacillin).
• No correlation was observed between mecA induction magnitude and ceftobiprole MICs.
• High oxacillin MICs (≥256 µg/ml) were associated with substantial oxacillin-induced mecA expression (≥13 fold) in 11 isolates.
• No association found between mecA induction levels and SCCmec type.

Conclusions:

• Ceftobiprole and oxacillin can induce mecA expression in MRSA.
• mecA induction levels do not consistently predict ceftobiprole resistance.
• High-level oxacillin resistance in some MRSA strains correlates with significant mecA induction.
• SCCmec type does not appear to influence the magnitude of mecA induction by these antibiotics.