Determining Antimicrobial Resistance in the Plastisphere: Lower Risks of Nonbiodegradable vs Higher Risks of Biodegradable Microplastics

The
plastisphere is a potential contributor to global antimicrobial
resistance (AMR), posing potential threats to public and environmental
health. However, comprehensively quantifying the contribution of microplastics
with different biodegradability to AMR is lacking. In this study,
we systematically quantified AMR risk mediated by biodegradable and
nonbiodegradable microplastics using abundance-based methods and a
custom AMR risk ranking framework that includes antimicrobial resistance
genes (ARGs) abundance, mobility, and host pathogenicity. Our results
demonstrated that biodegradable microplastics exhibited higher AMR
risk compared to that of nonbiodegradable plastics. Key resistance
genes, including those for multidrug, bacitracin, and aminoglycoside
resistance, were predominant. Machine learning analysis identified
cell motility as the most significant signature associated with AMR
risk, highlighting its potential role in promoting ARGs dissemination.
In addition, biodegradable microplastics promoted oxidative stress
and SOS responses, which likely enhanced horizontal gene transfer
(HGT) and AMR. Metagenome-assembled genomes (MAGs) analysis uncovered
the colocalization of microplastic degradation genes, ARGs, and virulence
factors (VFs), further supporting the elevated risk in biodegradable
plastisphere. The proximity of ARGs to mobile genetic elements (MGEs)
suggests that microplastic degradation processes might favor ARGs
mobility. These findings would contribute critical insights into AMR
dissemination in the plastisphere, emphasizing the need for integrated
environmental and public health strategies under the context of One
Health.