Department of Civil, Environmental and Architectural Engineering, University of Kansas, 4112 Learned Hall, 1530 West 15th Street, Lawrence, KS 66045, USA.
Water Res. 2010 Jul;44(13):3829-36. doi: 10.1016/j.watres.2010.04.041. Epub 2010 May 6.
Increased levels of bacterial resistance to antibiotics noted in recent decades poses a significant obstacle to the effective treatment and prevention of disease. Although overuse of antibiotics in agriculture and medicine is partially responsible, environmental exposure to heavy metals may also contribute to antibiotic resistance, even in the absence of antibiotics themselves. In this study, a series of eight lab-scale activated-sludge reactors were amended with Zn and/or a suite of three antibiotics (oxytetracycline, ciprofloxacin, and tylosin), in parallel with unamended controls. Classical spread-plating methods were used to assess resistance to these compounds in culturable bacteria over 21 weeks. After seven weeks of general acclimation and development of baseline resistance levels (phase 1), 5.0 mg/L Zn was added to half of the reactors, which were then operated for an additional 7 weeks (phase 2). For the final seven weeks (phase 3), two of the Zn-amended reactors and two of the control reactors were amended with all three antibiotics, each at 0.2 mg/L. Zn amendment alone did not significantly change resistance levels at the 95% confidence level in phase 2. However, tylosin resistance increased significantly during phase 3 in the Zn-only reactors and resistance to all three antibiotics significantly increased as a consequence of combined Zn+antibiotic amendments. Ambient dissolved Zn levels in the reactors were only 12% of added levels, indicating substantial Zn removal by adsorption and/or precipitation. These results show that sub-toxic levels of Zn can cause increased antibiotic resistance in waste treatment microbial communities at comparatively low antibiotic levels, probably due to developed cross-resistance resulting from pre-exposure to Zn.
近几十年来，细菌对抗生素的耐药性水平不断上升，这对疾病的有效治疗和预防构成了重大障碍。虽然抗生素在农业和医学中的过度使用是部分原因，但环境中重金属的暴露也可能导致抗生素耐药性，即使没有抗生素本身。在这项研究中，一系列八个实验室规模的活性污泥反应器分别用 Zn 和/或三种抗生素（土霉素、环丙沙星和泰乐菌素）进行了修正，同时也有未经修正的对照。经典的平板扩散法用于评估在 21 周内可培养细菌对这些化合物的耐药性。经过七周的一般驯化和基线耐药水平的发展（第 1 阶段），将 5.0mg/L 的 Zn 添加到一半的反应器中，然后再运行 7 周（第 2 阶段）。在最后七周（第 3 阶段），两个 Zn 修正的反应器和两个对照的反应器分别用三种抗生素中的两种进行了修正，每种抗生素的浓度为 0.2mg/L。Zn 单独修正在第 2 阶段在 95%置信水平下并没有显著改变耐药水平。然而，在 Zn 仅反应器中，泰乐菌素的耐药性在第 3 阶段显著增加，而由于 Zn+抗生素联合修正，对所有三种抗生素的耐药性也显著增加。反应器中环境溶解 Zn 水平仅为添加水平的 12%，表明 Zn 通过吸附和/或沉淀得到了大量去除。这些结果表明，在相对较低的抗生素水平下，亚毒性水平的 Zn 可以导致废水处理微生物群落中抗生素耐药性的增加，这可能是由于预先暴露于 Zn 导致交叉耐药性的发展。
