Dynamics of antibiotic resistance markers and Escherichia coli invasion in riverine heterotrophic biofilms facing increasing heat and flow stagnation

• Published in: The Science of the total environment 2023-10, Vol.893, p.164658-164658, Article 164658
• Main Authors: Gionchetta, G., Snead, D., Semerad, S., Beck, K., Pruden, A., Bürgmann, H.
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antimicrobial resistance; Biofilms; Drug Resistance, Microbial; Environmental stressors; Escherichia coli - genetics; Genes, Bacterial; Hot Temperature; Microbial invasion; River biofilm; Sequencing; Wastewater
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.164658

As motivation to address environmental dissemination of antimicrobial resistance (AMR) is mounting, there is a need to characterize mechanisms by which AMR can propagate under environmental conditions. Here we investigated the effect of temperature and stagnation on the persistence of wastewater-associated antibiotic resistance markers in riverine biofilms and the invasion success of genetically-tagged Escherichia coli. Biofilms grown on glass slides incubated in-situ downstream of a wastewater treatment plant effluent discharge point were transferred to laboratory-scale flumes fed with filtered river water under potentially stressful temperature and flow conditions: recirculation flow at 20 °C, stagnation at 20 °C, and stagnation at 30 °C. After 14 days, quantitative PCR and amplicon sequencing were used to quantify bacteria, biofilms diversity, resistance markers (sul1, sul2, ermB, tetW, tetM, tetB, blaCTX-M-1, intI1) and E. coli. Resistance markers significantly decreased over time regardless of the treatment applied. Although invading E. coli were initially able to colonize the biofilms, its abundance subsequently declined. Stagnation was associated with a shift in biofilm taxonomic composition, but there was no apparent effect of flow conditions or the simulated river-pool warming (30 °C) on AMR persistence or invasion success of E. coli. Results however indicated that antibiotic resistance markers in the riverine biofilms decreased under the experimental conditions in the absence of exposure to external inputs of antibiotics and AMR. [Display omitted] •Flume experiment shows that river biofilms downstream of wastewater effluent are invadable by E. coli.•E. coli invasion is transient regardless of varying environmental conditions.•Neither stagnancy nor high temperature increases persistence of antibiotic resistance markers.•Antibiotic resistance markers decrease in biofilm with no external stressors.•Microbial community composition in river biofilm diversifies with flow termination.