Antibiotic resistance among germs swells during droughts, study suggests

For as long as we’ve known that soil bacteria manufacture molecular weapons to fight each other, we’ve been swiping their battle plans. In clinics and hospitals, those turf-war weapons have become miraculous drugs of modern medicine—antibiotics—that blow away otherwise deadly infections.

But, of course, there’s a dark side of mimicking microbial munitions—bacteria have defenses, too, namely antibiotic resistance. You’re probably aware that we’re facing a rising threat of drug resistance among disease-causing bacteria, one that is rendering much of our stolen weaponry obsolete and making infections harder to defeat.

Often, this growing crisis is framed as a clinical failure: We’re overusing and misusing antibiotics, hastening our bacterial foes’ natural ability to develop and spread resistance. While this is certainly true, a new study in Nature Microbiology this week identifies a potentially new driver of rising antibiotic resistance—and we’re at least partly to blame for this one, too.

A series of experiments by researchers at the California Institute of Technology found that dry soil—drought conditions—consistently select for and enrich antibiotic resistance in soil bacterial communities. More concerningly, the researchers found that pro-resistance conditions in soil link to higher frequencies of antibiotic-resistant infections in hospitals around the world. And with human-driven climate change, drought conditions are expected to increase. Assuming the link is real, projections indicate that drought-threatened regions across the globe will face heightened emergence of antibiotic resistance.

While the authors acknowledge that more research is needed to confirm the connections, “our study offers a clear example of how climate change has the potential to intersect with microbial ecology to shape public health outcomes,” they conclude.

The underlying mechanism hypothesized to explain this connection is a fairly simple one: as soil dries, natural antibiotics produced by soil microbes reach higher concentrations in the remaining pockets of moisture. Those higher concentrations, in turn, select for bacteria that can resist the antibiotics.