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Survey of the antimicrobial activity of Australian honey

Antimicrobial activity of honey. Honey has been well studied for its antimicrobial and wound healing propertiesLow water activity~80% sugarsLow pHGluconic acidpH 3.2 ? 4.5Hydrogen peroxideGlucose oxidase. Antimicrobial activity of honey. Leptospermum honey. Leptospermum honey catalase. Brush box honey.

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Survey of the antimicrobial activity of Australian honey

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    1. Survey of the antimicrobial activity of Australian honey Julie Irish Dee Carter Shona Blair School of Molecular and Microbial Biosciences University of Sydney

    2. Antimicrobial activity of honey Honey has been well studied for its antimicrobial and wound healing properties Low water activity ~80% sugars Low pH Gluconic acid pH 3.2 – 4.5 Hydrogen peroxide Glucose oxidase

    4. Non-peroxide activity is caused by methylglyoxal (MGO) High concentrations of MGO in manuka honey that correlate strongly with non-peroxide activity MGO is naturally produced in all cells as a by-product of metabolism Highly toxic Modifies DNA, RNA, and proteins Targets them for degradation by the cell’s own machinery Some bacteria and fungi have well-defined detoxification systems

    5. How does this fit with the current theory about medicinal honey? MGO produced by stressed plants May explain why some organisms are more sensitive to honey than others Combination of MGO and honey makes it non-toxic to human cells? Need further studies on source, mode of action, standardisation in medicinal honeys Non-peroxide activity is caused by methylglyoxal (MGO)

    6. Survey of Australian honeys for antibacterial activity Important to find the most highly active honeys for therapeutic use 345 New Zealand honeys tested (Allen et al. (1991)) No published data for Australian honey Overview of activity of Australian honey

    7. Testing the antibacterial activity of honey Compares the antibacterial activity of a given honey to that of phenol Staphylococcus aureus is mixed into agar plate Holes cut into agar Various solutions added to wells 25% honey in water (tests total activity) OR 25% honey in catalase solution (tests non-peroxide activity) OR Solutions of 2 to 7% phenol (standard curve)

    8. Solutions diffuse out of the wells during incubation If they prevent the growth of S. aureus zones of inhibition Zones are measured, mean diameter squared Standard curve generated from phenol solutions Testing the antibacterial activity of honey

    9. Testing the antibacterial activity of honey

    10. Testing the antibacterial activity of honey

    11. Results 503 honey samples tested 477 Apis mellifera 26 Trigona spp. Activity (phenol equivalent) varies greatly <5 Insignificant therapeutic value 5-10 Low activity >10 Therapeutically beneficial >20 Highly active

    12. Total activity

    13. Total activity

    14. Total activity

    15. Total activity

    16. Total activity

    17. Total activity

    18. Total activity

    19. Total activity

    20. Total activity

    21. Total activity

    22. Total activity

    23. Total activity

    24. Distribution of total activity

    25. Non-peroxide activity

    26. Non-peroxide activity

    27. Non-peroxide activity

    28. Non-peroxide activity

    29. Non-peroxide activity

    30. Non-peroxide activity

    31. Non-peroxide activity

    32. Non-peroxide activity

    33. Non-peroxide activity

    34. Non-peroxide activity

    35. Distribution of non-peroxide activity

    36. Non-peroxide activity Of the 80 honeys with non-peroxide activity, 62 (77.5%) were from Leptospermum, or contained Leptospermum Mean non-peroxide activity 17.2 ? 4.1 (9.8 – 25.9) Some species/areas more reliable than others L. polygalifolium (Jelly bush): 29 samples, 28 had non-peroxide activity L. scoparium (Manuka): 11 samples, none had non-peroxide activity, some inactive Most active Leptospermum honeys from NSW-QLD border

    37. Non-peroxide activity 18 non-Leptospermum samples had non-peroxide activity Mean non-peroxide activity 10.1 ? 1.7 (8.1 – 15.9) Spotted gum (3/6 samples) South west Tasmanian wildflowers (3/5 samples) Stonefruit orchard (1/2 samples) Clover (1/5 samples) Melaleuca (2/28 samples) Moort (1/1 samples) Forest red gum (1/2 samples) Messmate (1/6 samples) Unspecified mixed flora (5/64 samples)

    38. Floral sources 477 honey samples from 142 different floral sources, including mixed flora 78% of honeys were from native Australian flora, another 17% were likely to contain natives 38% of honeys contained eucalypts 24% of honeys contained Leptospermum (likely to be biased)

    39. Eastern Australia

    40. Eastern Australia Highest total activity: 34.3 (Apple box/Red stringybark) Highest non-peroxide activity: 25.9 (Jelly bush) High non-peroxide activity (>20% phenol equivalent) in Leptospermum samples from QLD and northern NSW 12 non-Leptospermum honeys had non-peroxide activity

    41. Western Australia

    42. Western Australia Highest total activity: 31.9 (Stonefruit) Highest non-peroxide activity: 9.7 (Melaleuca) 31 honeys with total activity >20 (many from flora endemic to WA) Jarrah: 19 samples Activity range 17.7 to 31.4 1 sample was inactive Karri: 3 samples Activity range 18.5 to 29.6 Marri: 9 samples Activity range 18 to 29.7 1 sample was inactive

    43. Important message It is impossible to predict the activity of a given honey, must test every batch 32 samples, same beekeeper, same floral source, same time, different hives 31 samples had total activity between 11 and 19 1 sample was inactive 30% of Leptospermum honeys were inactive, 15% had hydrogen peroxide activity only Activity relates to floral source to an extent, but there are clearly many other factors involved Environmental conditions, soil type, soil and plant microbiology, bee health…

    44. Stingless bee honey 26 samples of Trigona spp. honey from QLD Mixed flora, various times of year 23 samples had total activity >20 (12.4 – 32.1) 24 samples had non-peroxide activity >10 (11.5 – 23.7)

    45. Conclusions Australian honeys show a wide range of antibacterial activities Many have potential for therapeutic use Non-peroxide activity exists in honeys from various floral sources Leptospermum spp. remain the most reliable source of high non-peroxide activity Statistical analysis is ongoing Identified areas to focus on in future studies Role of MGO?

    46. Acknowledgments The 124 beekeepers who supplied honey samples for the survey Rob Manning, Dept of Agriculture, WA Tim Heard, CSIRO Entomology, QLD Comvita, New Zealand RIRDC

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