Clouds Capable of Disseminatimg Antibiotic-Resistance Genes

The atmosphere is a huge dissemination route for bacteria bearing antibiotic-resistance genes. Clouds can transport these genes, according to a team of researchers from Université Laval and Université Clermont Auvergne.

This is the first study to show that clouds harbor antibiotic resistance genes of bacterial origin in concentrations comparable to other natural environments.”

Florent Rossi, Study First Author and Postdoctoral Fellow, Université Laval

Florent Rossi belongs to the team of Caroline Duchaine, a professor at the Faculty of Science and Engineering and a researcher at the Quebec Heart and Lung Institute-Université Laval.

The researchers sampled clouds at the peak of the Puy de Dôme, a dormant volcano in France’s Massif Central, to examine this phenomenon. Over the course of two years, the scientists used high-flow rate “vacuums” to sample clouds at an atmospheric research station 1,465 m above ground.

On average, these samples had around 8,000 bacteria per milliliter of cloud water, according to analysis.

These bacteria usually live on the surface of vegetation or soil. They are aerosolized by the wind or by human activities, and some of them rise into the atmosphere and participate in the formation of clouds.”

Florent Rossi, Study First Author and Postdoctoral Fellow, Université Laval

The quantities vary, ranging from 330 to over 30,000 bacteria per milliliter of cloud water. Between 5% and 50% of these bacteria may be alive and potentially aggressive.

Various Sources

The researchers used all of their data to calculate the concentration of 29 subtypes of antibiotic-resistance genes in atmospheric air masses. Each milliliter of cloud water contained an average of 20,800 copies of antibiotic-resistance genes.

Oceanic clouds and continental clouds each have their signature of antibiotic resistance genes. For example, continental clouds contain more antibiotic resistance genes used in animal production.”

Florent Rossi, Study First Author and Postdoctoral Fellow, Université Laval

Although airborne transport of antibiotic resistance genes is a natural phenomenon, the increasing use of antibiotics in agriculture and medicine has led to the spread of these resistant strains.

“Our study shows that clouds are an important pathway for antibiotic-resistance genes spreading over short and long ranges. Ideally, we would like to locate emission sources resulting from human activities to limit the dispersal of these genes,” Florent Rossi notes.

Future studies will look into the health effects of the spread of these antibiotic-resistant genes.