French and Canadian researchers have recently observed that clouds promote the proliferation of bacteria carrying genes for resistance to antibiotics.
- Clouds are an important source of dissemination of antibiotic resistance genes, according to a Franco-Canadian study.
- According to this new research, the clouds analyzed contained, on average, 8,000 bacteria per milliliter of cloud water.
- The airborne transport of antibiotic resistance genes is a natural phenomenon, but the frequent use of antibiotics in agriculture and medicine has favored the spread of these resistant strains.
In a recent study published in the journal Science of The Total Environmentscientists from Laval University (Canada) and Clermont-Auvergne University (France) observed that clouds are an important pathway for the dissemination of antibiotic resistance genes.
Between 5% and 50% of the bacteria present in the clouds are alive and potentially active
To reach this conclusion, the teams sampled clouds at the top of Puy de Dôme, France, at 1,465 meters above sea level. Nearly twelve cloud sampling sessions were carried out over two years. They were carried out using two devices: a cloud impactor, which collects micro-droplets of water in suspension, and a high-speed vacuum cleaner, which fixes the nucleic acids present in the clouds.
According to the analysis results, the clouds contained, on average, 8,000 bacteria per milliliter of cloud water. “The bacteria that were there usually live on the surface of the vegetation or in the soil (…) They are aerosolized by the wind or by human activities, and some of them rise in the atmosphere and participate to cloud formation. The concentrations that we have measured are very variable. They range from 330 to 30,000 bacteria per milliliter of cloud water. Between 5% and 50% of these bacteria are alive and potentially active”said Florent Rossi, first author of the study and postdoctoral fellow in the Department of Biochemistry, Microbiology and Bioinformatics at Laval University and at the Research Center of the University Institute of Cardiology and Pneumology of Quebec.
Nearly 9 antibiotic resistance gene subtypes identified
During the study, the researchers also determined the trajectory and altitude of the air masses associated with the clouds during the 72 hours preceding the sampling. They identified two types of clouds: oceanic clouds, which originated directly from the Atlantic Ocean, and continental clouds, which had circulated more over land and had been exposed to local environments.
“Our samples contained, on average, 20,800 copies of antibiotic resistance genes per milliliter of cloud water. We detected 29 subtypes of antibiotic resistance genes. Ocean clouds and continental clouds each have a signature of antibiotic resistance genes of their own. Thus, continental clouds contain more genes of resistance to antibiotics used in animal production”said Florent Rossi.
As the scientist explained, the airborne transport of antibiotic resistance genes is a natural phenomenon, but the frequent use of antibiotics in agriculture and medicine has favored the spread of these resistant strains. “Our study shows that clouds are an important pathway for the dispersal of antibiotic resistance genes, over both short and long distances. Ideally, we would like to be able to locate emission sources attributable to human activities in order to limit the dispersal of these genes”noted the researchers in a statement from the University of Laval.
