Antimicrobial effects, and selection for AMR by non-antibiotic drugs in a wastewater bacterial community

Area of Science:

• Environmental microbiology
• Antimicrobial resistance
• Ecotoxicology

Background:

• Antimicrobial resistance (AMR) poses a global health threat, exacerbated by co-selection from various environmental contaminants.
• Non-antibiotic drugs (NADs) are emerging as potential co-selectors of AMR, but their effects on complex microbial communities at environmentally relevant concentrations are poorly understood.

Purpose of the Study:

• To investigate the antimicrobial effects and AMR co-selection potential of common environmental NADs (diclofenac, metformin, 17-β-estradiol) on a complex bacterial community.
• To assess these effects across a range of concentrations, including those found in the environment.

Main Methods:

• Utilized a combination of culture-based methods, whole metagenome sequencing, and metatranscriptomics.
• Exposed a mixed bacterial community to varying concentrations of diclofenac, metformin, and 17-β-estradiol.
• Quantified antimicrobial effects and analyzed shifts in the resistome and community composition.

Main Results:

• Diclofenac, metformin, and 17-β-estradiol significantly inhibited bacterial community growth at concentrations of 50 µg/L, 26 µg/L, and 24 µg/L, respectively.
• Only 17-β-estradiol showed evidence of selecting for an antimicrobial resistance marker.
• No clear selection for antibiotic resistance genes was observed via metagenomics, but increases in metal resistance genes (e.g., arsB) were noted after NAD exposure.

Conclusions:

• Environmentally relevant concentrations of NADs can impact bacterial community growth and function.
• NADs may influence the selection of specific metal resistance genes within microbial communities.
• Further research is needed to fully understand the complex interactions between NADs, microbial communities, and the spread of antimicrobial resistance.