We assessed the
Medicinal honeys are registered for topical application in several countries and are formulated in tubes, into ointments and gels, and made into wound dressings. A common medicinal honey is Manuka honey, from the Manuka bush (
Manuka honey has
In medical practice, Manuka honey might be delivered in combination with traditional antibiotics, with both being administered topically or with Manuka honey being administered topically and the traditional antibiotic(s) being administered systemically. Therefore, it is useful to understand the interaction between Manuka honey and conventional antibiotics. Jenkins and Cooper reported a synergistic interaction between oxacillin and Manuka honey against a single strain of
Our goals were to evaluate the activity of Manuka honey with antibiotics against biofilm bacteria and to visualize effects of Manuka compared to artificial honey on biofilms using electron microscopy.
Active Manuka Honey UMF 16+ (Manuka Honey USA LLC, Orlando, FL
The effect of Manuka honey and vancomycin alone and in combination against
The fractional biofilm eradication concentration (FBEC) of vancomycin or gentamicin in combination with Manuka honey was calculated as follows [
The FBEC of Manuka honey was calculated as follows:
The two FBEC values were added to give the
The following day, the discs for electron microscopy were placed in 2.5 mL of Trump’s solution (4% formaldehyde and 1% glutaraldehyde in a phosphate buffer, pH 7.3) and refrigerated. The discs for quantitative culture were dipped in sterile water for 1 minute and placed in 2.5 mL TSB in a test tube, vortexed for 30 seconds, and bath sonicated for 5 minutes. Quantitative cultures were performed by plating five serial ten-fold dilutions in TSB onto sheep blood agar plates which were incubated overnight. The concentration of bacteria was calculated to determine which discs to examine using electron microscopy, and the respective discs in Trump’s solution were submitted for scanning electron microscopy at the Mayo Clinic scanning electron microscopy core facility. Following critical-point drying and gold-palladium sputter coating, disks were imaged by cold-field emission scanning electron microscopy using a Hitachi S-4700 electron microscope (Hitachi Ltd., Tokyo, Japan).
The MIC and the MBEC of Manuka honey against
We showed that subinhibitory Manuka honey concentrations increased vancomycin’s activity against
MBEC of antibiotic | MBEC of Manuka honey |
|
|||
---|---|---|---|---|---|
Alone | With Manuka honey | ||||
|
500 µg/mL | 100 µg/mL with 17.5% Manuka honey | 30% | 17.5% with 100 µg/mL gentamicin | 0.78 |
75 µg/mL with 20% Manuka honey | 20% with 75 µg/mL gentamicin | 0.82 | |||
|
|||||
|
100 µg/mL | 1 µg/mL with 1% Manuka honey | 3% | 1% with 1 µg/mL vancomycin | 0.34 |
Although it has been suggested that Manuka honey may improve the activity of conventional antibiotics against planktonic bacteria [
Teflon discs with
Images of
Scanning electron microscopy of
Scanning electron microscopy of
Images of
Scanning electron microscopy of
Scanning electron microscopy of
Few investigators have visualized effects of Manuka honey on bacteria using electron microscopy, and to the best of our knowledge, none have done so with biofilm bacteria. Henriques et al. performed scanning electron microscopy on planktonic
Together, our results show that Manuka honey has visually appreciable activity against established
Manuka honey has
The authors declare that there is no conflict of interests regarding the publication of this paper.