Manuka Honey Too Sweet For Bacteria’s Taste

In Medical & Diagnostic

Great news for Australian and New Zealand beekeepers! For generations, naturopaths have been promoting the power of natural Manuka honey as an antiseptic.

Now researchers at the University of Southampton have found even heavily diluted Manuka honey is effective in stopping the growth of bacterial biofilms, the extremely thin and usually very resilient layer of microbes that accrete and adhere to surfaces including industrial quality plastic used in medical devices.

Manuka honey is a monofloral honey from the nectar of the manuka tree, which only grows in Australian and New Zealand. For the first time, Manuka honey has been confirmed as having antibacterial and anti-inflammatory properties.

In future, Australian and New Zealand Manuka beekeepers may find their product being used in patients with fitted with medical devices carrying a high risk of infection such as urinary catheters, according to the online Journal of Clinical Pathology. Each year, upwards of 100 million catheters are sold worldwide with one in four hospital patients being fitted with one. Frequently however, long-term catheter use comes with complications such as inflammation and infections.

As Associate Professor Bashir Lwaleed, of the University of Southampton, who led the study confirmed, “We have been able to demonstrate that diluted honey is potentially a useful agent for reducing biofilm formation on indwelling plastic devices such as urinary catheters. Catheter infection rates can account for a large proportion of hospital acquired infections — it is an area of clinical practice that needs addressing. We hope that these results may offer an alternative way of preventing such infections. We believe that patients might also benefit from honey’s anti-inflammatory properties, which are generally stronger in dark honeys, such as Manuka and that antibacterial resistance is unlikely to be a factor when honey is used.”

In demonstrating Manuka honey’s potential application for fighting the growth of hazardous biofilms, the research team grew strains of the most common bacteria responsible for the majority of urinary tract infections linked with long-term catheter use, Escherichia coli and Proteus mirabilis on plastic plates in their laboratory.

Manuka honey was diluted with distilled water and applied to the bacterial cultures in different strengths, ranging from 3.3 per cent, to 6.6 per cent, 10 per cent, 13.3 per cent, and 16.7 per cent.

Initially, the diluted honey was added at the same time as the bacteria to two of the wells in each of the 96 plates used in the study. Plain and half strength Manuka honey were used as controls in the test. The plates were sealed and incubated for 24. 48 and 72 hours to gauge the effect honey had on biofilm formation.

The second phase of the research focused on establishing if Manuka honey could halt the growth of the biofilm. Honey was added after the bacteria had been growing for 24 hours and then incubated for a further 4 or 24 hours. Results of the experiments clearly demonstrated Manuka honey inhibited the bacteria’s ‘stickiness’, and thus the biofilm’s growth. Even the lowest dilution (3.3 per cent) reduced ‘stickiness’ by 35 per cent after 48 hours compared with the plain and artificial honey.

After three days, all dilutions suppressed biofilm development by around 70 per cent with the biggest impact being the 16.7 per cent dilution, which reduced growth by 77 per cent.

The results of phase two of the study was similar with the 16.7 per cent dilution restricting growth by 38 per cent after 4 hours and by 46 per cent after 24 hours. The impact was increased after 48 hours with the exception of the 3.3 per cent and 6.6 per cent dilutions.

Summary

While the initial results were pleasing, the study was limited to the stickiness of bacteria and early biofilm development and was conducted under laboratory conditions. Next step would be to trial the honey in clinical conditions replicating the flow of liquid in the bladder to clarify its suitability for field applications.