For a team of Canadian and French researchers, dark clouds on the horizon are potentially ominous not because they signal an approaching storm – but because they were found in a recent study to carry drug-resistant bacteria over long distances.
“These bacteria usually live on the surface of vegetation like leaves, or in soil,” lead author Florent Rossi said in interview.
“We found that they are carried by the wind into the atmosphere and can travel long distances – around the world – at high altitudes in clouds,” he told AFP.
The discovery was published in last month’s edition of the journal Science of The Total Environment.
The researchers from Laval University in Quebec City and Clermont Auvergne University in central France searched for antibiotic-resistant genes from bacteria found in cloud samples.
The samples were taken from an atmospheric research station perched 1,465 meters (4,806 feet) above sea level atop the Puy de Dome summit, a dormant volcano in central France between September 2019 and October 2021.
An analysis of the retrieved mist revealed that they contained between 330 to more than 30,000 bacteria per milliliter of cloud water, for an average of around 8,000 bacteria per milliliter.
They also identified 29 subtypes of antibiotic-resistant genes in the bacteria.
The study offered no conclusions on the potential health effects of the spread in the atmosphere of antibiotic-resistant bacteria – estimating that only 5 percent to 50 percent of the organisms could be alive and potentially active.
But Rossi suggested the risks are likely low.