Manuka honey useful to curb bacteria growth in urinary catheters

London, Sep 28 (IANS) Manuka honey can be used to curb growth of bacterial biofilms in medical devices like urinary catheters which carry a high infection risk, finds a study.

Manuka honey is a monofloral honey produced in Australia and New Zealand from the nectar of the manuka tree.

Bacterial biofilms are a thin but resilient layer of microbes that build up on and stick to any surface, including plastic.

"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," said Bashir Lwaleed, Associate Professor, University of Southampton.

To find out if Manuka honey has a role in stopping the establishment and development of biofilms, the researchers cultured strains of Escherichia coli and Proteus mirabilis bacteria — two bacteria account for most of the urinary tract infections on plastic plates in the laboratory.

The honey was diluted with distilled water and added to medium to give different ‘strengths’: 3.3 per cent, 6.6 per cent, 10 per cent, 13.3 per cent, and 16.7 per cent.

In the first part of the experiment, the various dilutions were added at the same time as the bacteria in two of the wells of each of the 96 plates, and just plain medium or artificial half strength honey to the other two wells.

These were then sealed and incubated for 24, 48, and 72 hours to see whether the honey had any effect on the formation of a biofilm.

In the second part of the experiment, honey was added after 24 hours and incubated for either a further 4 or 24 hours to see if honey restricted growth of the biofilm.

The results, published in the Journal of Clinical Pathology showed that Manuka honey strongly inhibited the ‘stickiness’ of the bacteria, and therefore the development of a biofilm.

Even at the lowest dilution of 3.3 per cent, it curbed stickiness by 35 per cent after 48 hours compared with the plain medium and artificial honey.

But the greatest effect was seen after three days and at a dilution of 16.7 per cent, when stickiness had been reduced by 77 per cent. All the dilutions suppressed this by around 70 per cent after three days.

As to the impact of Manuka honey on further growth, the 16.7 per cent dilution restricted growth by 38 per cent after 4 hours and by 46 per cent after 24 hours. The impact was even stronger after 48 hours, but not for the weaker dilutions of 3.3 per cent and 6.6 per cent.