Metagenomic insight into airborne pathogenic microorganisms community and antibiotic resistomes in Belgrade during spring season

Introduction: In recent years, it has been recognized that air is an important transmission route for antibiotic resistance genes (ARGs). In addition, airborne pathogens could be part of particle matter (PM2.5), which is an indicator of air pollution. The intertwining of these two serious health threats poses an additional risk to public health. Objective: To examine the abundance and diversity of pathogens and resistomes in air samples collected during the spring season of 2024 at two locations in the Belgrade metropolitan area selected as highly polluted during the heating season. Method: Outdoor air was sampled at two locations (Borca and Zemun Ugronovacka) using polyethersulfone membrane filters (air volume of 30 m3). Collected DNA samples were subjected to shotgun metagenome sequencing (Illumina Novaseq X plus) and bioinformatic analysis (Novogene, UK). Pathogens and ARGs were annotated using PHI and CARD databases, respectively. Findings: Both airborne metagenomes showed similar patterns of significant human and animal pathogens (Salmonella enterica, Pseudomonas aeruginosa, Staphylococcus aureus, Mycobacterium tuberculosis, Escherichia coli, Acinetobacter baumannii), and plant pathogens (Xanthomonas oryzae, Fusarium graminearum, Xanthomonas campestris, Erwinia amylovora). The most abundant ARG in the airborne metagenomes was blaTEM, but genes conferring resistance to aminoglycosides (aac(2’)-Ic), beta-lactams (blaOXA-129, blaC, cepA, cfxA2), fluoroquinolones (mfpA), fosfomycin (murA), macrolides (ermF, mphE), tetracyclines (tet(Q)), vancomycin (vanH, vanT, vanY, vanW) and disinfectants (cepA, qacG) were also detected. Moreover, the gene encoding multidrug resistant efflux pump adeF was present in both metagenomes. Conclusion: This study revealed that Belgrade air could represent a reservoir for pathogenic microorganisms and antimicrobial resistance.