左氧氟沙星在蒙脱石存在条件下对大肠杆菌的毒性效应

采用批实验研究了蒙脱石对左氧氟沙星的吸附机理及对左氧氟沙星抗菌作用的影响。结果表明,中性条件下存在培养基时,左氧氟沙星在蒙脱石上前2 h即达到吸附平衡,吸附等温线符合Langmuir吸附方程,吸附率达90%以上;蒙脱石吸附左氧氟沙星存在阳离子交换作用、氢键作用、疏水作用、阳离子键桥作用、静电吸附作用等物理化学过程;蒙脱石本身不具有抑菌、杀菌活性,且由于蒙脱石增大了微生物附着的比表面积,在特定情况下可以促进微生物的生长;扣除其对微生物生长的促进作用后,蒙脱石吸附左氧氟沙星降低了后者的毒性效应,其抑菌率降低约25%。上述结果为进一步研究抗生素在环境中的毒理效应提供了基础依据。

The Toxic Effect of Levofloxacin on Escherichia coli with Montmorillonite

This study focused on determining the mechanisms of the adsorption of levofloxacin to montmorillonite, and the toxic effect of levofloxacin on Escherichia coli in the presence of montmorillonite using batch experiments was also investigated. The toxicity of adsorbed levofloxacin on microbial growth was also studied. The results showed that, under neutral condition, containing culture medium, the adsorption of levofloxacin on montmorillonite reached the equilibrium in the first 2 h, which was well fitted to the Langmuir isotherm, and the percentage of adsorption was above 90%. During the adsorption, many physical and chemical processes were included, such as cation exchange, hydrogen bonding, hydrophobic interaction, cationic bridging, and electrostatic interactions. Montmorillonite did not have antibacterial activity, and it could promote the growth due to the increasing of the surface area of the microbial adhesion in certain case. The inhibition rate of levofloxacin on the growth of Escherichia coli decreased by 25%, which was not including the impact of the promotion on Escherichia coli growth by montmorillonite. The results presented in the study will provide basic foundation for the toxicity of antibiotics in the environment.