Triclosan is an antimicrobial agent that is widespread throughout the environment, but little information is available that explains how triclosan impacts the microbial communities where it is found in greatest abundance: anaerobic digesters. Lab-scale reactors were operated to determine how triclosan impacts the community structure (based on ARISA), function (methane production) and antimicrobial resistance genes in anaerobic digesters. Previously-exposed (to triclosan) communities were amended with 5, 50, and 500 mg/kg of triclosan, corresponding to the median, 95th percentile, and 4x-maximum triclosan concentration detected in US biosolids. Triclosan amendment caused community structures to shift away from control reactors, and the time to reconvergence corresponded with triclosan concentration. The 500 mg/kg-amended reactors did not reconverge with control reactors, and methane production significantly decreased (p-value = 0.002). At 50 mg/kg, a large variability in methane production was observed, suggesting that 50 mg/kg may be a tipping point where communities start to lose their ability to adapt. When previously unexposed communities were exposed to 500 mg/kg, function was maintained, but the abundance of a gene encoding for cross-resistance to triclosan (mexB) increased. This research suggests that, when present in anaerobic microbial communities, triclosan will either inhibit function or select for resistant bacteria.

Impacts of triclosan on methanogenic community structure, function, and antimicrobial resistance

247th National Meeting (2014)

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