Seasonal Patterns in Mobile Colistin Resistance Gene Variants in Wastewater Bioaerosols and Liquid Sludge

To
address the growing threat of global antimicrobial resistance,
a one-health approach is needed to understand the complex socioecological
cycling of antibiotic resistance genes. In this study, a metagenomics
approach using DNA shotgun sequencing, metagenome assembly, and antibiotic
resistance gene (ARG) annotation was used to examine seasonal patterns
in the abundance of mobile colistin resistance (mcr) gene variants in bioaerosols and liquid sludge in three wastewater
treatment plants (WWTPs). ARGs represented 0.2–0.8 and 0.1–0.2%
of the bioaerosol and liquid sludge metagenomes, respectively, while mcr genes represented 0–0.3 and 0–0.5% of
the identified ARGs in bioaerosol and liquid sludge metagenomes. Seven
of the ten known mcr variants were detected in wastewater
bioaerosol and liquid samples, with mcr-5 and mcr-8 being the most prevalent across all seasons and sites.
Additional functional and taxonomic annotation of mcr-containing metagenomic contigs showed that mcr genes
were often located on contigs with other co-occurring ARGs and mobile
genetic elements and may be harbored by opportunistic human pathogens
and other bacterial taxa not previously associated with mcr genes. Atmospheric dispersion modeling showed that mcr-containing bioaerosols can be transported kilometers away from the
WWTPs, resulting in the possible dissemination of these ARGs into
surrounding environments and communities.