Long-term study on spatiotemporal prevalence, distribution, and diversity of clinically relevant and environmental Acinetobacter species in Canadian agricultural watersheds

This study, conducted between 2018 and 2024, expands upon prior research through a culture-based investigation of the spatiotemporal prevalence, distribution, and diversity of Acinetobacter species across nine sites in an agriculturally-dominated watershed in eastern Ontario, Canada. Spatial analyses revealed, compared to medium to large stream order sites and forested reference site, agricultural drainage ditches consistently displayed higher Acinetobacter prevalence, cell concentrations, and diversity, likely due to direct proximity to livestock farms. Summer exhibited the highest Acinetobacter abundance and diversity, a pattern potentially linked to elevated temperatures, water stagnation, and seasonal runoff. Species-level identification revealed the widespread and persistent detection of several human health-associated species, including A. baumannii and A. pittii. The association of Acinetobacter species with upstream urban and agricultural land uses suggests that anthropogenically influenced waters may serve as critical sources for the environmental dissemination of pathogenic Acinetobacter and antimicrobial resistance genes. Furthermore, environmental Acinetobacter species, such as A. calcoaceticus, A. guillouiae, A. johnsonii, and A. soli, may play underappreciated roles in gene transfer and infection risk. This first in-depth analysis of Acinetobacter species within an agricultural aquatic ecosystem, offering a foundation for future research into environmental reservoirs of potential human pathogens and the spatiotemporal factors shaping microbial populations.