Pathogenic Bacteria Are the Primary Determinants Shaping PM_2.5-Borne Resistomes in the Municipal Food Waste Treatment System

Bioaerosol pollution poses a substantial threat to human health during municipal food waste (FW) recycling. However, bioaerosol-borne antibiotic-resistant genes (ARGs) have received little attention. Herein, 48 metagenomic data were applied to study the prevalence of PM_2.5-borne ARGs in and around full-scale food waste treatment plants (FWTPs). Overall, FWTP PM_2.5 (2.82 ± 1.47 copies/16S rRNA gene) harbored comparable total abundance of ARGs to that of municipal wastewater treatment plant PM_2.5 (WWTP), but was significantly enriched with the multidrug type (e.g., AdeC/I/J; p < 0.05), especially the abundant multidrug ARGs could serve as effective indicators to define resistome profiles of FWTPs (Random Forest accuracy >92%). FWTP PM_2.5 exhibited a decreasing enrichment of total ARGs along the FWTP-downwind-boundary gradient, eventually reaching levels comparable to urban PM_2.5 (1.46 ± 0.21 copies/16S rRNA gene, N = 12). The combined analysis of source-tracking, metagenome-assembled genomes (MAGs), and culture-based testing provides strong evidence that Acinetobacter johnsonii-dominated pathogens contributed significantly to shaping and disseminating multidrug ARGs, while abiotic factors (i.e., SO₄^2-) indirectly participated in these processes, which deserves more attention in developing strategies to mitigate airborne ARGs. In addition, the exposure level of FWTP PM_2.5-borne resistant pathogens was about 5-11 times higher than those in urban PM_2.5, and could be more severe than hospital PM_2.5 in certain scenarios (<41.53%). This work highlights the importance of FWTP in disseminating airborne multidrug ARGs and the need for re-evaluating the air pollution induced by municipal FWTP in public health terms.