Chronic Exposure to an Environmentally Relevant Triclosan Concentration Induces Persistent Triclosan Resistance but Reversible Antibiotic Tolerance in Escherichia coli

作者：Mingzhu Li, Yuning He, Jing Sun, Jing Li, Junhong Bai, Chengdong Zhang · 发表于：Environmental Science & Technology · 年份：2019 · DOI：10.1021/acs.est.8b06763 · 被引用次数：83 · 研究领域：Antimicrobial agents and applications、Antimicrobial Peptides and Activities、Pharmaceutical and Antibiotic Environmental Impacts

The major concern regarding the biocide triclosan (TCS) stems from its potential coselection for antibiotic resistance. However, environmental impacts are often investigated using high concentrations and acute exposure, while predicted releases are typified by chronic low concentrations. Moreover, little information is available regarding the reversibility of TCS and derived antibiotic resistance with diminishing TCS usage. Here, the model Gram-negative bacterium Escherichia coli was exposed to 0.01 mg/L TCS continuously for more than 100 generations. The adapted cells gained considerable resistance to TCS as indicated by a significant increase in the minimal inhibitory concentration (MIC 50 ) from 0.034 to 0.581 mg/L. This adaptive evolution was attributed to overexpression and mutation of target genes (i.e., fabI ) as evidenced by transcriptomic and genomic analyses. However, only mild tolerance to various antibiotics was observed, possibly due to reduced membrane permeability and biofilm formation. After TCS exposure ceased, the adapted cells showed persistent resistance to TCS due to inheritable genetic mutations, whereas their antibiotic tolerance declined over time. Our results suggest that extensive use of TCS may promote the evolution and persistence of TCS-resistant bacterial pathogens. A quantitative definition of the conditions under which TCS selects for multidrug resistance in the environment is crucially needed.