Wednesday, September 10, 2014

Bee Bacteria may be an Alternative to Antibiotics

Raw honey has been used to treat infections for centuries, and today we are very aware of the extent of its antimicrobial properties, though we still don't know what it is exactly that makes honey so effective (the best idea right now is honey's osmolarity and hydrogen peroxide content).  Six years ago, a group of researchers in Sweden discovered a large, unexplored bacterial microbiota in the honey stomach of honeybees, which was made up of 40 lactic acid bacterial strains, 9 strains of Lactobacillus, and 4 strains of Bifidobacterium.  The researchers hypothesized that this microbiota, specifically the lactic acid bacteria (LAB), were responsible for the antimicrobial properties of honey.  The group report (in an open access study published this week) having finally found the answer.

Lactic acid bacteria produce lactic acid during fermentation, and many species also produce bioactive compounds like organic acids, free fatty acids, ethanol, benzoate, hydrogen peroxide, and antibiotic compounds.  Every single member of the LAB strains found in the microbiota of honeybees is involved in the nectar-to-honey process in bees.  However, only 13 strains of LAB were present in varying numbers depending on the quality and source of the nectar, the health of the bees, and the presence of other microorganisms.  These LABs also produce and secrete a number of bioactive compounds which they use to protect themselves against other microorganisms.  The study looked at these 13 strains of LAB and their effects on multi-drug resistant bacteria (which are common wound pathogens), including MRSA (Methycillin-resistant Staphylococcus aureus), Pseudomonas aeruginosa, and VRE (vancomycin-resistant Enterococcus).  The authors also studied LAB metabolites and proteins in fresh honey, supplied by a local beekeeper.

Table showing the different levels of metabolites produced
by the 13 LAB strains
The authors found that each of the pathogenic bacteria were inhibited by the compounds secreted by the LAB of honeybees.  Each LAB strain produced different antibiotic metabolites (right), causing varying degrees of growth inhibition in the pathogenic bacteria.  In some cases, the antibiotic properties of the LAB strains were more effective at inhibiting growth than commonly-used antibiotics (like vancomycin, ampicillin, and ciprofloxacin).  Further, 9 LAB-produced proteins were also detected in the samples of fresh honey, which did not seem to degrade over time.

The researchers believe that the strong results lie in the broad-spectrum of active compounds produced by the LAB, which are able to target a wide range of pathogenic bacteria.  Currently, antibiotics are made of one active substance, making them only effective on certain pathogenic bacteria.  Other wound treatments, like iodine and silver dressings, are associated with environmental and/or patient-related hazards.  The authors suggest that using fresh honey, or store-bought honey with added LAB, could be an environmentally-friendly, non-toxic alternative to other antibiotic treatments.  The authors hope to start clinical trials soon.

Store-bought honey does not contain live LAB, and so the antimicrobial properties of this processed honey are not as great as you would find when buying fresh honey.  That's because store-bought honey is heated, and often only contains 20% water, preventing LAB growth.  Fresh honey has a water content of 22-30%; while this is still quite low for LAB survival, they do manage to live for a few weeks in the harvested honey.

Here's a video of researcher Eile Butler, one of the authors of the study, describing the effectiveness of the LAB in wound-healing:

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