We often admire the beauty and tranquility of clouds, but did you know that they can also harbor dangerous bacteria that are resistant to antibiotics? A new study by researchers from Canada and France has revealed that clouds can transport these bacteria over long distances and potentially spread them around the world.

The study, published in the journal Science of The Total Environment1, analyzed cloud samples collected from an atmospheric research station on top of a dormant volcano in central France. The samples were taken between September 2019 and October 2021, and contained between 330 to more than 30,000 bacteria per milliliter of cloud water.

The researchers identified 29 subtypes of antibiotic-resistant genes in the bacteria, which means that they can survive or even thrive in the presence of antibiotics. Antibiotic resistance is a major global health threat, as it makes it harder to treat infections and increases the risk of mortality and morbidity.

The researchers believe that these bacteria originate from the surface of vegetation or soil, where they are exposed to antibiotics used in agriculture or health care. They are then lifted into the atmosphere by the wind and carried by clouds over long distances. The study found that some of the bacteria came from as far as Asia and North America.

The implications of this discovery are not yet clear, but the researchers suggest that atmospheric monitoring could help identify the sources and routes of these bacteria, and limit their dispersal. They also reassure that the risk of infection from these bacteria is likely low, as most of them are environmental bacteria that are not harmful to humans, and only a small fraction of them are alive and active in the clouds.

So next time you look at the sky, remember that there is more than meets the eye. Clouds are not only beautiful, but also complex ecosystems that can influence the biosphere and the climate. And they may also carry some unwanted passengers that could pose a challenge for our health.