Global Survey of Antibiotic Resistance Genes in Air

Despite
its emerging significant public health concern, the presence
of antibiotic resistance genes (ARGs) in urban air has not received
significant attention. Here, we profiled relative abundances (as a
fraction, normalized by 16S rRNA gene) of 30 ARG subtypes resistant
to seven common classes of antibiotics, which are quinolones, β-lactams,
macrolides, tetracyclines, sulfonamides, aminoglycosides, and vancomycins,
in ambient total particulate matter (PM) using a novel protocol across
19 world cities. In addition, their longitudinal changes in PM2.5 samples in Xi’an, China as an example were also
studied. Geographically, the ARGs were detected to vary by nearly
100-fold in their abundances, for example, from 0.07 (Bandung, Indonesia)
to 5.6 (San Francisco, USA). The β-lactam resistance gene blaTEM was found to be most abundant, seconded by quinolone
resistance gene qepA; and their corresponding relative
abundances have increased by 178% and 26%, respectively, from 2004
to 2014 in Xi’an. Independent of cities, gene network analysis
indicates that airborne ARGs were differentially contributed by bacterial
taxa. Results here reveal that urban air is being polluted by ARGs,
and different cities are challenged with varying health risks associated
with airborne ARG exposure. This work highlights the threat of urban
airborne transmission of ARGs and the need of redefining our current
air quality standards in terms with public health.