Global dispersal and potential sources of antibiotic resistance genes in atmospheric remote depositions

Abstract

Antibiotic resistance has become a major Global Health concern and a better understanding on the global spread mechanisms of antibiotic resistant bacteria (ARB) and intercontinental ARB exchange is needed. We measured atmospheric depositions of antibiotic resistance genes (ARGs) by quantitative (q)PCR in rain/snow collected fortnightly along 4 y. at a remote high mountain LTER (Long-Term Ecological Research) site located above the atmospheric boundary layer (free troposphere). Bacterial composition was characterized by 16S rRNA gene sequencing, and air mass provenances were determined by modelled back trajectories and rain/snow chemical composition. We hypothesize that the free troposphere may act as permanent reservoir and vector for ARB and ARGs global dispersal. We aimed to i) determine whether ARGs are long-range intercontinental and persistently dispersed through aerosols, ii) assess ARGs long-term atmospheric deposition dynamics in a remote high mountain area, and iii) unveil potential diffuse ARGs pollution sources. We showed that the ARGs sul1 (resistance to sulfonamides), tetO (resistance to tetracyclines), and intI1 (a proxy for horizontal gene transfer and anthropogenic pollution) were long-range and persistently dispersed in free troposphere aerosols. Major depositions of tetracyclines resistance matched with intensification of African dust outbreaks. Potential ARB mostly traced their origin back into agricultural soils. Our study unveils that air masses pathways are shaping ARGs intercontinental dispersal and global spread of antibiotic resistances, with potential predictability for interannual variability and remote deposition rates. Because climate regulates aerosolization and long-range air masses movement patterns, we call for a more careful evaluation of the connections between land use, climate change and ARB long-range intercontinental dispersal

This research is included within the global surveillance activities of the Long-Term Ecological Research node Aigüestortes (LTER-AT) and was supported by Grant ECOSENSOR-BIOCON 04/009 from BBVA Foundation; Grants AERBAC 079/2007, AERBAC-2 178/2010, and DISPERSAL 829/2013 from the Spanish Office for the Environment’s-National Parks Research Programme (OAPN); and INTERACTOMA RTI2018-101205-B-I00 from the Spanish Agency of Research (AEI-MICINN) and European funding (ERDF) to EOC. JC was supported by PTA2018-016527-I (AEI-MICINN) and XTM by grant INTERACTOMA. CB wish to thank the support from the Economy and Knowledge Department of the Catalan Government through Consolidated Research Group (ICRA-ENV 2017 SGR 1124)