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Expression of mecA increases daptomycin tolerance in Staphylococcus aureus
Elizabeth V K Ledger1,2, Mario Recker3,4, Ruth C Massey1,2,5
1School of Microbiology, University College Cork, Cork, Ireland.
Mbio
|September 22, 2025
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) exhibits increased daptomycin tolerance due to the mecA gene. This gene reduces toxin release, allowing bacterial lipids to inactivate daptomycin, compromising treatment efficacy.
Area of Science:
- Microbiology
- Infectious Diseases
- Pharmacology
Background:
- Staphylococcus aureus bacteremia is a significant health concern with high mortality rates.
- Methicillin-resistant S. aureus (MRSA) infections are challenging due to resistance to beta-lactams via PBP2a encoded by mecA.
- Daptomycin is a crucial antibiotic for MRSA infections, but its effectiveness is limited by resistance and tolerance.
Purpose of the Study:
- To investigate the mechanisms underlying daptomycin tolerance in MRSA compared to methicillin-susceptible S. aureus (MSSA).
- To determine the role of the mecA gene in daptomycin tolerance and its impact on antibiotic efficacy.
- To elucidate the relationship between mecA, Agr quorum sensing, phenol-soluble modulins, and daptomycin inactivation.
Main Methods:
- Comparative analysis of daptomycin tolerance in clinical MRSA and MSSA isolates.
- Construction and analysis of a mecA transposon mutant.
- Assessment of Agr quorum sensing activity and phenol-soluble modulin (PSM) toxin levels.
- Evaluation of daptomycin inactivation by bacterial lipids.
Main Results:
- MRSA strains exhibit significantly higher daptomycin tolerance than MSSA strains.
- The presence of the mecA gene is directly responsible for increased daptomycin tolerance.
- mecA downregulates Agr quorum sensing, reducing PSM toxin release, which in turn allows bacterial lipids to inactivate daptomycin.
- Expression of mecA in MSSA strains increases daptomycin tolerance by reducing toxin production.
Conclusions:
- The mecA gene contributes to daptomycin tolerance in MRSA by disrupting the Agr system and PSM toxin production, leading to enhanced daptomycin inactivation.
- This study reveals a novel mechanism by which MRSA evades last-resort antibiotic therapy, impacting treatment strategies.
- Understanding the interplay between mecA, toxin production, and daptomycin efficacy is crucial for managing MRSA infections and developing new therapeutic approaches.
