Death by a thousand cuts: how antibacterial clays kill

OMT blue clay
A section of blue clay from the open pit mine at the Oregon Mineral Technologies clay deposit near Crater Lake. The antibacterial blue clay is surrounded by white clay which lacks antibacterial properties. (Credit: Keith Morrison)

By now most of you will have heard that more and more bacteria are becoming impervious to the many life-saving antibiotics on which we’ve come to rely. In November, scientists in China sampling bacteria from meat and hospitalized patients found a new gene called MCR-1 that confers resistance to colistin, a drug that is currently used as a last resort when all other antibiotics have failed. This report was the latest in a series of increasingly worrisome news that have spurred researchers to look for new ways to combat antimicrobial resistance. While some scientists are exploring futuristic ideas like light-activated nanoparticles, others are looking to nature and literally digging up dirt for inspiration.

In a paper published recently in Scientific Reports, researchers have revealed for the first time the mechanism behind the antibacterial properties of medicinal clay.

“People have been eating clays for thousands of years,” says Dr. Keith Morrison, the report’s lead author and now a postdoctoral fellow at the Lawrence Livermore National Laboratory. The purported benefits of eating clay relate to its ability to grab heavy metals and other “toxins” and expel them from your body. However, the scientific evidence supporting this idea (and the idea that our bodies need any detoxing at all) is lacking.

As a PhD student at Arizona State University, Morrison was interested in another curious property of some medicinal clays—their ability to kill bacteria. While the use of clay to treat wounds and skin infections can be traced back to the 19th century, the scientific study of these antibacterial clays is a fairly new field. Continue reading


Combining drugs with different penetration profiles can accelerate development of multidrug resistance

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What scares you? As a kid, I hid behind couch cushions while watching Jurassic Park and could never finish a Goosebumps book. Nowadays, I am terrified of the growing epidemic of antimicrobial resistance. And I’m not the only one. Last year, as part of a five-year strategy to combat drug resistance, British Prime Minister David Cameron commissioned a review to examine the economic and health costs of antimicrobial resistance. In their first report published last December, the panel predicted that left unchecked, antimicrobial resistance will lead an extra 100 million deaths by 2050 and cost the world economy up to $100 trillion USD.

Efforts to halt the spread of antimicrobial resistance have focused on removing antibiotics from animal feed and curtailing the overzealous and oftentimes unnecessary use of antibiotics in humans. Another strategy to prevent resistance from developing is combination therapy, when two or more drugs with unique modes of action are taken together to treat an infection. In a paper published this week in the Proceedings of the National Academy of Sciences, a team of mathematicians and biologists led by Dr. Pleuni Pennings at San Francisco State University examined how differences in drug penetrance can impact the effectiveness of combination therapy and subsequent emergence of multidrug resistance.

Combination therapy reduces the risk of drug resistance because in theory, the pathogen needs to acquire multiple mutations at the same time to withstand the assault of multiple drugs. In reality, combination therapies fail to stem the development of resistance for a number of reasons. For example, some patients are started on a single drug first before a second drug is added. This type of treatment regiment facilitates resistance development because bacteria can acquire singular mutations in a stepwise fashion. Another reason is that different drugs have different staying power, which means that even though you may be taking both drugs at the same time, one could pass through your body much faster than the other. This creates periods of “effective monotherapy” where resistance can develop easily to the single long-lived drug. While a lot of attention has been paid to how drugs with different half-lives impact resistance, not a lot is known about how the spatial distribution of drugs influence the evolution of multidrug resistance. That’s where this paper comes in.  Continue reading

Between the Pages: Missing Microbes

Welcome to the first instalment of Between the Pages, where I read and review books about science. 

Missing Microbes:  How the overuse of antibiotics is fueling our modern plagues. By Martin J. Blaser, MD. (HarperCollins)
Missing Microbes: How the overuse of antibiotics is fueling our modern plagues. By Martin J. Blaser, MD. (Source)

If science was Hollywood, the microbiome would be its new It Girl. The paparazzi report on its every move to see which new disease or condition it will be associated with next. Fans clamor to buy the newest supplement that promises to restore your microbiome to a “healthy” state.

Feeling a bit late to the party? Let’s bring you up to speed. Simply put, the human microbiome is the collection of microorganisms that share our body. These include the bacteria, viruses, and fungi that live on our skin, in our mouths and digestive tracts, and in all our bodies’ little nooks and crannies. Even though they are microscopic in size, their numbers are daunting: there are 10 microbial cells for every human cell in our body! Most of these microorganisms are beneficial to us. They help us digest food and extract nutrients that we wouldn’t be able to get on our own. They strengthen our immune system so that it can better recognize and fight off invading pathogens. They prevent harmful microbes from taking hold in our bodies by depriving them of important nutrients. So, that’s great! Three cheers for our microbiome!

But what happens when our microbiome changes and the balance of species is shifted? As Dr. Martin Blaser argues in his book Missing Microbes, that’s when things start to go wrong. Continue reading