纳米氧化物对耐四环素屎肠球菌的毒性研究及机制初探

A Preliminary Exploration for Toxicity and Mechanism of Nano Metal Oxides to Tetracycline Resistant Enterococcus faecium

城镇污水处理厂是废弃纳米材料在环境中重要的收纳场所,在水处理过程中存在与另一类新污染物耐药细菌及其抗性基因充分接触并相互作用的机会。尽管纳米材料对包括细菌在内的各种生物的毒性效应被普遍报道,然而对耐药细菌的毒性及风险的影响鲜有研究。本研究考察了3种污水中广泛存在的纳米氧化物对耐四环素屎肠球菌的毒性,并探索了纳米氧化物种类、粒径、浓度和在水中的赋存时间等因素的影响。结果表明,3种纳米氧化物的毒性大小为nCuO>nZnO>nTiO_(2);纳米氧化物对耐四环素屎肠球菌的毒性随浓度和粒径的提高均呈现先升高后降低的趋势,如在50 mg·L^(-1)和40 nm处nTiO_(2)毒性达到最高;赋存时间越长,纳米氧化物对耐四环素屎肠球菌的毒性越强。从影响机理看,纳米氧化物刺激显著提升了细胞膜的通透性,破坏细胞膜,导致细胞破裂死亡。本文可为阐明污水中广泛共存的纳米材料对耐药细菌的影响提供支撑。

Urban wastewater treatment plants are important reservoirs of waste nanomaterials in the environment.Nano metal oxides(NMOs)can contact and interact extensively with another emerging contaminants,antibiotic resistant bacteria(ARB)and antibiotic resistance genes(ARGs)during wastewater treatment process.Despite of frequent reports on the toxicity of nanomaterials to a variety of organisms including bacteria,few studies have been conducted yet on the toxicity of nanomaterials on ARB.In this study,the toxicity of NMOs to tetracycline-resistant Enterococcus faecium(TRE)was examined,and influences of NMOs’type,size,concentration and persistent period on the toxicity were explored.Results showed that the toxicity of NMOs followed the order of nCuO>nZnO>nTiO_(2).The toxicity of NMOs on TRE increased with NMOs’concentration and size,reaching the highest at 50 mg·L^(-1)and 40 nm(nTiO_(2)),and then decreased finally.Furthermore,the toxicity of NMOs increased with the persistent period.As for the mechanism,NMOs substantially increased the permeability of TRE,destroyed cell membranes,and induced the rupture and death of cells.This study can be helpful in elucidating the effect of widely co-existing nano metal oxides in wastewater on antibiotic resistant bacteria.