Bacteria carrying antibiotic-resistance genes can use the atmosphere as a wide-reaching channel for dissemination. Scientists from Université Laval and Université Clermont Auvergne have demonstrated that clouds can transport these genes.

"This study represents a breakthrough in demonstrating that clouds contain antibiotic resistance genes originating from bacteria, at levels similar to those found in other natural settings," remarked Florent Rossi, the study's primary author and a postdoctoral researcher in Caroline Duchaine's team at the Faculty of Science and Engineering at Université Laval. Duchaine is also a researcher at the Quebec Heart and Lung Institute-Université Laval.

In order to observe this occurrence, the research team collected cloud samples from the summit of Puy de Dôme, a dormant volcano situated in France's Massif Central. At an atmospheric research station positioned 1,465 meters above ground level, the scientists carried out 12 cloud sampling sessions using high-flow rate "vacuum" devices over the course of two years.

The samples that were collected and analyzed showed an average of around 8,000 bacteria per milliliter of cloud water. "These bacteria are typically found on the surfaces of soil or vegetation. They become airborne through wind or human activities and can ascend into the atmosphere, contributing to cloud formation," elucidated Florent Rossi. The concentration of bacteria varied between 330 and over 30,000 per milliliter of cloud water. Out of these bacteria, between 5% and 50% could be alive and capable of being active.

Various sources 

Based on their findings, the researchers assessed the concentration of 29 different subtypes of antibiotic-resistance genes present in atmospheric air masses. On average, the clouds contained 20,800 copies of antibiotic-resistance genes per milliliter of cloud water.

Florent Rossi clarified, "Antibiotic resistance genes present in oceanic clouds and continental clouds have distinct signatures. For instance, antibiotic resistance genes utilized in animal production are more prevalent in continental clouds."

While the airborne transportation of antibiotic resistance genes is a natural process, the excessive use of antibiotics in both agriculture and medicine has significantly augmented the prevalence of these resistant strains and their propagation in the environment.

The research findings have demonstrated that clouds serve as a critical conduit for the dissemination of antibiotic-resistance genes over both short and long distances. "Our goal is to identify the sources of emission resulting from human activities so that we can mitigate the dispersion of these genes," expressed the research team.

Future research will need to investigate the health implications of the dissemination of these antibiotic-resistant genes.  (PB/Newswise)