Commonly prescribed medicines antagonise anti-MRSA antibiotics and select for resistance

Area of Science:

• Microbiology
• Pharmacology
• Infectious Diseases

Background:

• Many non-antibiotic medications possess uncharacterized antimicrobial properties.
• The impact of these off-target effects on antibiotic efficacy is largely unknown.
• Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat.

Purpose of the Study:

• To investigate the antimicrobial activity of common UK prescription medicines against MRSA.
• To determine the mechanisms by which these drugs affect bacterial growth and antibiotic efficacy.
• To assess the potential for these drugs to accelerate antibiotic resistance development.

Main Methods:

• Screening of eight widely prescribed UK medicines for antimicrobial activity against MRSA.
• Analysis of drug mechanisms including membrane disruption and stress response induction.
• Transposon mutant screening to identify pathways affected by simvastatin.
• Checkerboard assays to evaluate drug interactions with antibiotics like vancomycin and daptomycin.
• Assessment of resistance development following prolonged drug exposure.

Main Results:

• Simvastatin, amlodipine, and fluoxetine demonstrated growth inhibitory effects on MRSA.
• These drugs were found to disrupt bacterial membranes and induce stress responses.
• Simvastatin inhibits cell wall synthesis by targeting the mevalonate pathway.
• Antagonistic interactions were observed: simvastatin reduced vancomycin and beta-lactam efficacy, amlodipine reduced vancomycin and daptomycin efficacy, and fluoxetine reduced vancomycin efficacy.
• Prolonged exposure accelerated resistance to vancomycin and daptomycin.

Conclusions:

• Commonly prescribed non-antibiotic drugs can exhibit antimicrobial activity and interfere with antibiotic treatments.
• These interactions may compromise the effectiveness of essential antibiotics against MRSA.
• The findings highlight the need for further research into drug-drug interactions and their implications for antimicrobial stewardship, especially with rising MRSA treatment failures.