Massive amounts of antibiotic resistance genes found in clouds
A study published in Science of the Total Environment1 revealed clouds carry large quantities of various bacterial antibiotic resistance genes. Generated by antibiotics released into the environment, these genes can travel long distances.
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Each year, tens of thousands of tons of antibiotics are used for healthcare purposes in humans, animals, and plants, a portion of which is released into the environment. Antibiotics are thus found not only in wastewater, but also in rivers, the sea, and soil, enabling environmental bacteria to acquire resistance genes that can then be transferred to other bacteria. Bacterial cells and genetic material can aerosolize and, due to air turbulence, rise into the atmosphere, travel long distances, and then become part of the water cycle.
Antibiotic resistance has been classified as one of the 10 biggest threats for human societies in the near future.
Proof of a “resistome” in the clouds
A French and Canadian research team assessed the quantity of antibiotic resistance genes in clouds at the Puy de Dôme meteorological observatory in France’s Massif Central, at an altitude of 1,465 meters. Twelve samples were taken with a high-flow vacuum between September 2019 and October 2021, revealing an average concentration of around 5,400 copies of resistance genes per cubic meter of air (measured by flow cytometry). The 33 resistance genes found correspond to the main antibiotic families in use today: quinolones, sulfonamides, tetracyclines, aminoglycosides, glycopeptides, β-lactam antibiotics, and macrolides. Of these, 29 were detected at least once, and 6 were observed in at least 75% of samples.
6 things you should know about antibiotics
Rather than varying with the seasons, the distribution of these genes varied according to the geographical origin of the air masses. Resistance genes for the quinolone family, antibiotics strongly implicated in antibiotic resistance and whose use has been restricted in Europe since 2018, were more abundant in high marine clouds. Resistance genes for the sulfonamide and tetracycline families were more abundant in clouds formed over continental surfaces, perhaps due to their widespread use in livestock farming.
4.95 million In 2019, >4.95 million deaths were associated with antimicrobial resistance
1.27 million In 2019, 1.27 million were directly attributed to antibiotic-resistant bacterial infections
The atmosphere is a major highway for resistome dissemination
Considering the average concentration of resistance genes in clouds according to the study (5,400/m3 of air), the researchers estimate that clouds permanently carry around 2.53 × 1021 copies of resistance genes worldwide. Thus, each year, between 1.29 × 1025 and 2.06 × 1026 resistance genes may be transported by clouds, with a very large quantity of these genes (2.2 ×1024) falling to earth through precipitation (and a fraction remaining evaporated in the atmosphere).
This study has found the atmosphere to be one of the routes by which antibiotic resistance factors are disseminated worldwide. Studies that pinpoint the sources of bacterial emissions may limit their dispersal.2
Infographics to share with your patients
What is the World AMR Awareness Week?
Each year, since 2015, the WHO organizes the World AMR Awareness Week (WAAW), which aims to increase awareness of global antimicrobial resistance.
Held on 18-24 November, this campaign encourages the general public, healthcare professionals and decision-makers to use antimicrobials carefully, to prevent the further emergence of antimicrobial resistance.
