Many household products, such as toothpastes and hand soaps, contain the antibacterial agent triclosan. When these products are used, triclosan enters the municipal wastewater treatment system, where activated sludge bacteria are exposed to it. The goal of this project is to assess the impact of exposure to sub-lethal doses of triclosan on the diversity of antibiotic resistance genes in wastewater-derived bacteria. Enrichment cultures were prepared from samples of activated sludge bacteria that were obtained from a full-scale treatment facility, and grown in triplicate in a synthetic wastewater medium with triclosan concentrations of 0, 1, 5 or 15 µg/L. After seven weeks of growth, fosmid libraries were constructed from each culture. Antibiotic selection was carried out on Luria Bertani agar plates supplemented with antibiotics from the major classes. Unique resistant clones were identified, and their antibiotic resistance profiles were quantified through minimum inhibitory concentration (MIC) assays. At present, 29 unique resistant clones have been isolated, representing resistance to six of the thirteen antibiotics that were tested. Of these clones, two are resistant to multiple antibiotics: one is resistant to carbenicillin, ampicillin, and ceftazidime, while the other is resistant to carbenicillin and rifampicin. One of the resistance genes was determined to be 98% identical to a type B1 metallo-β-lactamase from a member of the species <i>Elizabethkingia</i>. Whole fosmid sequencing will be done to determine the mechanism of resistance used by the other clones.<br/>

Investigating the diversity of antibiotic resistance genes in cultures derived from activated sludge bacterial communities following exposure to low doses of triclosan

253rd National Meeting (2017)

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