Antibiotic resistance among germs swells during droughts, study suggests

Since we learned that soil bacteria make molecular weapons to fight each other, we have swept aside their battle plans. In clinics and hospitals, these weapons of turf warfare have become modern medicine’s miraculous drugs – antibiotics – that eliminate otherwise deadly infections.

But of course, there is a dark side to imitating microbial munitions: bacteria also have defenses, namely antibiotic resistance. You probably know that we face a growing threat of drug resistance among pathogenic bacteria, a threat that is rendering many of our stolen weapons obsolete and making infections more difficult to defeat.

Often, this growing crisis is presented as a clinical failure: we overuse and overuse antibiotics, accelerating the natural ability of our bacterial enemies to develop and spread resistance. While that’s certainly true, a new study out this week in Nature Microbiology identifies a potential new driver of growing antibiotic resistance — and we’re at least partly to blame for it, too.

A series of experiments by researchers at the California Institute of Technology found that dry soils – drought conditions – systematically select for and enrich antibiotic resistance in soil bacterial communities. Even more worrying, researchers found that conditions favorable to resistance in the soil were linked to higher frequencies of antibiotic-resistant infections in hospitals around the world. And with human-caused climate change, drought conditions are expected to worsen. Assuming the link is real, projections indicate that regions of the world threatened by drought will face increased emergence of antibiotic resistance.

Although the authors acknowledge that more research is needed to confirm these links, “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 thought to explain this link is quite simple: As soil dries, natural antibiotics produced by soil microbes reach higher concentrations in remaining pockets of moisture. These higher concentrations in turn select for bacteria capable of resisting antibiotics.