Thursday, March 3, 2011
Honey: It's not just for snacks anymore
Today's science is about two kinds of bugs: bees (okay, honey) and antibiotic-resistance bacteria. First, for the bees: It's not common these days to read good news on apiarian issues. Colony collapse disorder dominates that circuit, though researchers are getting closer to cracking the mystery of what's behind the disappearing honeybees. So it's refreshing to find something positive about bees, even if the news is actually about honey and only indirectly related to the black and yellow-striped stingers.
Now, for the microscopic bugs: You wouldn't expect something as humble as bee spit to show up in the highly technical world of antibiotic resistance research. Unfortunately, the battle against drug-resistant bugs isn't going well. Methicillin-resistant Staphylococcus aureus (MRSA) is knocking off more than 18,000 Americans each year. Multidrug-resistant and extensively drug-resistant tuberculosis crop up regularly in the poor, crowded regions of our planet. Even an organism as exhaustively well-studied as E. coli is finding its way around formerly potent antibiotics.
(Drug resistance isn't limited to bacteria--consider the uselessness of quinine against most modern strains of malaria. But the term "antibiotics" is generally used synonymously with "antibacterials", so we'll just focus on the prokaryotes for the time being.)
Scientists and health care professionals are growing increasingly desperate; the development of new antibiotics is notoriously slow, and the rapid generation time of most bacteria ensures that mutations conferring drug resistance will show up eventually. So it's not altogether surprising that researchers are turning to more unorthodox methods like phage therapy and natural antibacterials like honey.
Honey has a long history as a topical antimicrobial agent, but its non-food uses have been largely forgotten in the developed world. Neosporin just feels so much more science-y.
Besides, there are downsides to using honey for curing wounds. It can harbor pathogenic spores (hence why you shouldn't feed it to infants) and potential allergens like pollen, and its effectiveness can vary from batch to batch, even within a single hive.
What makes honey a germ-buster? For starters, it's really, really sweet. All that sugar gives it a high osmolarity, which bacteria do not appreciate. It's the same concept behind why strawberry jam stays fresh in your fridge long after the actual strawberries would have spoiled.
Honey's also got hydrogen peroxide and an antimicrobial peptide called bee defensin-1 (more on those in a second). It has a low pH, ranging from 3.2-4.5 (the pH of pure water is 7; lower pH's are acidic, higher ones are basic). And some honeys have high concentrations of methylglyoxal (MGO), a compound with antibacterial and possible cancer-fighting properties.
Peroxide and bee defensin-1 both act by breaching the membranes of bacteria, like marauders tearing down a fortress's protective walls. This is problematic for bacteria because, as Carl Zimmer eloquently put it in his book Microcosm, "Even a small hole is big enough to make E. coli explode. If you prick us, we bleed, but if you prick E. coli, it blasts." (That holds true for many if not most bacteria). Peroxide can also wreak havoc inside a cell, pulling apart proteins with wild abandon.
All these antimicrobial factors spell certain death for most bacteria. However, even filtered, medical-grade honey produced under standardized greenhouse conditions isn't effective in practice against some of the nastier pathogens around today, such as MRSA and extended-spectrum beta-lactamase (ESBL)-producing E. coli.
Netherlands researcher Paul Kwakman and his team are investigating how to turn honey into a drug, so to speak, that's practical against antibiotic-resistant superbugs. While undiluted honey can kill some of these germs in a few hours, "In a moist wound, the honey could become so diluted that it no longer works," Kwakman recently told PhysOrg.
To get around the dilution problem, Kwakman's team decided to amp up the bactericidal nature of honey, supplementing it with synthetic antimicrobials (in this case, Bactericidal Peptide 2 (BP2)). Boosting the natural germ-fighting compounds in honey wasn't feasible: hydrogen peroxide kills human skin cells at higher concentrations, slowing wound healing; more MGO may be toxic; the bee defensin-1 molecule is too complicated to synthesize; and honey is already super-saturated with sugar.
Honey on its own kills some bacteria efficiently, and solo BP2 does the same. When combined with the sweet stuff, BP2 doesn't work quite as well, but the enriched honey's capacity to slaughter microbes is ramped up and works on a more species of bacteria, even at high dilutions. That's good news for applying it to mere flesh wounds.
Existing antibiotics are still more effective against many pathogens, and if MRSA or another drug-resistant skin-infecting bug gets into your bloodstream, an IV of honey probably isn't going to help you heal. Still, in the war against antibiotic-resistant bacteria, the prospects of enriched honey are abuzz with promise.
Recipe: Honey on toast
1. Carefully slice some bread.
2. Toast the bread.
3. Spread some honey on the bread.
4. If you ignored the admonition to be careful in step 1, dab some honey on your cut finger.