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Published on: September 8, 2021
Antibacterial activity of a new, stable, aqueous extract of allicin against methicillin-resistant Staphylococcus
1University of East London, School of Health and Bioscience, Stratford Campus, Romford Road, London E15 4LZ, UK. r.cutler@uel.ac.uk
Abstract:
The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in hospitals and the community has led to a demand for new agents that could be used to decrease the spread of these bacteria. Topical agents such as mupirocin have been used to reduce nasal carriage and spread and to treat skin infections; however, resistance to mupirocin in MRSAs is increasing. Allicin is the main antibacterial agent isolated from garlic, but natural extracts can be unstable. In this study, a new, stable, aqueous extract of allicin (extracted from garlic) is tested on 30 clinical isolates of MRSA that show a range of susceptibilities to mupirocin. Strains were tested using agar diffusion tests, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Diffusion tests showed that allicin liquids produced zone diameters >33 mm when the proposed therapeutic concentration of 500 microg/mL (0.0005% w/v) was used. The selection of this concentration was based on evidence from the MIC, MBC and agar diffusion tests in this study. Of the strains tested, 88% had MICs for allicin liquids of 16 microg/mL, and all strains were inhibited at 32 microg/mL. Furthermore, 88% of clinical isolates had MBCs of 128 microg/mL, and all were killed at 256 microg/mL. Of these strains, 82% showed intermediate or full resistance to mupirocin; however, this study showed that a concentration of 500 microg/mL in an aqueous cream base was required to produce an activity equivalent to 256 microg/mL allicin liquid.
Insights
A stable garlic extract, allicin, shows potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). This new allicin formulation effectively combats MRSA strains, including those resistant to mupirocin, offering a promising alternative topical agent.
Area of Science:
- Microbiology
- Pharmacology
- Natural Product Chemistry
Background:
- Rising prevalence of methicillin-resistant Staphylococcus aureus (MRSA) necessitates novel antimicrobial agents.
- Increasing mupirocin resistance in MRSA strains limits current topical treatment options.
- Allicin, a garlic-derived compound, possesses antibacterial properties but natural extracts lack stability.
Purpose of the Study:
- To evaluate the efficacy of a new, stable, aqueous allicin extract against clinical isolates of MRSA.
- To determine the antimicrobial activity of allicin against MRSA strains with varying susceptibilities to mupirocin.
Main Methods:
- Agar diffusion tests were performed to assess bacterial inhibition zones.
- Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays were conducted.
- Thirty clinical MRSA isolates with diverse mupirocin susceptibilities were tested.
Main Results:
- Allicin liquid at 500 microg/mL produced zone diameters >33 mm in diffusion tests.
- 88% of MRSA isolates had an allicin MIC of 16 microg/mL; all were inhibited at 32 microg/mL.
- 88% of isolates had an allicin MBC of 128 microg/mL; all were killed at 256 microg/mL.
Conclusions:
- A stable aqueous allicin extract demonstrates significant bactericidal activity against MRSA.
- Allicin is effective against MRSA strains exhibiting intermediate or full resistance to mupirocin.
- A 500 microg/mL concentration in an aqueous cream base achieved activity equivalent to 256 microg/mL allicin liquid.
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