Comparing the selective and co-selective effects of different antimicrobials in bacterial communities

• Published in: International journal of antimicrobial agents Vol. 53; no. 6; pp. 767 - 773
• Main Authors: Murray, Aimee K., Zhang, Lihong, Snape, Jason, Gaze, William H.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-06-2019; Elsevier Science Publishers
• Subjects: Anti-Infective Agents - pharmacology; Antibiotic; Antimicrobial; Bacteria - classification; Bacteria - drug effects; Bacteria - genetics; Benzalkonium Compounds - pharmacology; Biocide; Biota - drug effects; Ciprofloxacin - pharmacology; Drug Resistance, Bacterial; Evolution; Evolution, Molecular; Genes, Bacterial; Metagenomics; Resistance; Selection, Genetic; Trimethoprim - pharmacology; Waste Water - microbiology; Antimicrobial; Resistance; Metagenomics; Evolution; Antibiotic; Biocide
• ISSN: 0924-8579; 1872-7913
• DOI: 10.1016/j.ijantimicag.2019.03.001

•Selective and co-selective effects of antimicrobials were compared for the first time.•Ciprofloxacin and trimethoprim were more co-selective than selective.•Benzalkonium chloride (BAC) did not select for antibiotic/metal/qac resistance genes.•Metagenomics could identify highly co-selective compounds for further study.
Bacterial communities are exposed to a cocktail of antimicrobial agents, including antibiotics, heavy metals and biocidal antimicrobials such as quaternary ammonium compounds (QACs). The extent to which these compounds may select or co-select for antimicrobial resistance (AMR) is not fully understood. In this study, human-associated, wastewater-derived bacterial communities were exposed to either benzalkonium chloride (BAC), ciprofloxacin or trimethoprim at sub-point-of-use concentrations for one week to determine selective and co-selective potential. Metagenome analyses were performed to determine effects on bacterial community structure and prevalence of antibiotic resistance genes (ARGs) and metal or biocide resistance genes (MBRGS). Ciprofloxacin had the greatest co-selective potential, significantly enriching for resistance mechanisms to multiple antibiotic classes. Conversely, BAC exposure significantly reduced relative abundance of ARGs and MBRGS, including the well characterised qac efflux genes. However, BAC exposure significantly impacted bacterial community structure. Therefore BAC, and potentially other QACs, did not play as significant a role in co-selection for AMR as antibiotics such as ciprofloxacin at sub-point-of-use concentrations in this study. This approach can be used to identify priority compounds for further study, to better understand evolution of AMR in bacterial communities exposed to sub-point-of-use concentrations of antimicrobials.