Benzalkonium chloride alters phenotypic and genotypic antibiotic resistance profiles in a source water used for drinking water treatment

• Published in: Environmental pollution (1987) 2020-02, Vol.257, p.113472, Article 113472
• Main Authors: Harrison, Katherine R., Kappell, Anthony D., McNamara, Patrick J.
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - analysis; Anti-Infective Agents - pharmacology; Antibiotic resistant bacteria; Antimicrobial; Bacteria - drug effects; Benzalkonium Compounds - analysis; Ciprofloxacin - pharmacology; Drinking Water - microbiology; Drug Resistance, Bacterial - drug effects; Drug Resistance, Microbial - genetics; Environmental Monitoring; Genes, Bacterial - drug effects; Quaternary ammonium compounds; Sulfamethoxazole - pharmacology; Triclosan; Waste Water - microbiology; Water Microbiology; Water Pollutants, Chemical - analysis; Water Purification
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2019.113472

Antibiotic resistance is a major public health concern. Triclosan is an antimicrobial compound with direct links to antibiotic resistance that was widely used in soaps in the U.S. until its ban by the U.S. Food and Drug Administration. Benzalkonium chloride (BAC), a quaternary ammonium compound, has widely replaced triclosan in soaps marketed as an antibacterial. BAC has been detected in surface waters and its presence will likely increase following increased use in soap products. The objective of this study was to determine the effect of BAC on relative abundance of antibiotic resistance in a bacterial community from a surface water used as a source for drinking water treatment. Bench-scale microcosm experiments were conducted with microbial communities amended with BAC at concentrations ranging from 0.1 μg L−1 to 500 μg L−1. Phenotypic antibiotic resistance was quantified by culturing bacteria in the presence of different antibiotics, and genotypic resistance was determined using qPCR to quantify antibiotic resistance genes (ARGs). BAC at concentrations ranging from 0.1 μg L−1 to 500 μg L−1 was found to positively select for bacteria resistant to ciprofloxacin and sulfamethoxazole, and negatively select against bacteria with resistance to six other antibiotics. Exposure to BAC for 14 days increased the relative abundance of sul1 and blaTEM. This study re-highlights the importance of employing both culture and non-culture-based techniques to identify selection for antibiotic resistance. The widespread use of BAC will likely impact antibiotic resistance profiles of bacteria in the environment, including in source waters used for drinking water, wastewater treatment plants, and natural waterways. [Display omitted] •Benzalkonium chloride (BAC) altered the antibiotic resistance profiles of bacteria in surface water.•BAC positively selected for bacteria resistant to ciprofloxacin and sulfamethoxazole.•BAC selected against bacteria resistant to cephalexin, chloramphenicol, and streptomycin.•Exposure to BAC over time showed increased relative abundance of the resistance genes sul1 and blaTEM. Benzalkonium chloride (BAC) positively selected for bacteria resistant to ciprofloxacin and sulfamethoxazole and selected against bacteria resistant to cephalexin, chloramphenicol, and streptomycin in a surface water. Exposure to BAC over time increased relative abundance of the resistance genes sul1 and blaTEM.