洛美沙星和诺氟沙星对水中生物反硝化过程的影响模拟试验

近年来水环境中硝酸盐污染与抗生素污染的现象引起了人们的广泛关注,但目前复合抗生素污染对反硝化过程产生的影响并不明确。本研究以水环境中检出率较高的诺氟沙星和洛美沙星为代表进行模拟实验,探究ng级的两种抗生素复合对反硝化过程的影响。硝氮和亚硝氮的降解情况表明,实验浓度条件下,洛美沙星、诺氟沙星单用与二者联用对水环境中的反硝化过程存在不同的抑制作用。洛美沙星单用前期轻微促进反硝化,后期表现抑制作用,而诺氟沙星单用始终表现出抑制作用;洛美沙星和诺氟沙星联用抑制作用小于诺氟沙星单用,联用表现为拮抗作用。各体系的抑制作用大小为诺氟沙星>诺氟沙星+洛美沙星>洛美沙星。该模拟试验条件虽与实际条件有所差异,但在一定程度上表明抗生素联用表现出拮抗作用与反硝化体系内微生物数量、活性,反硝化酶活性,反硝化菌优势物种Achromobacter xylosoxidans、Acinetobacter baumannii、Pseudomonas sp.KY及功能基因nosZ和aac的丰度的变化有关。抗生素加入反硝化体系后会产生持续的影响,随反应时间的增加,反硝化菌逐渐适应有低浓度抗生素存在的环境,喹诺酮类抗生素耐药基因数量增加,微生物的耐药性增强,反硝化菌在数量和活性、反硝化酶活性及微生物群落层面均有回升趋势。

Effects of lomefloxacin and norfloxacin on the biological water denitrification process—an experimental study

Nitrate and antibiotic pollutions in water have attracted much attention in recent years, but the effects of combination antibiotic pollution on the biological water denitrification process is not clear. To address this issue, we tested norfloxacin and lomefloxacin under simulated experimental conditions. The $text{NO}_{3}^{-}$-N and $text{NO}_{2}^{-}$-N degradation results showed that lomefloxacin and norfloxacin had different inhibitory effects on water denitrification: Lomefloxacin promoted denitrification slightly in the early stage but inhibited it later on, whereas norfloxacin only inhibited it. Lomefloxacin combined with norfloxacin were less inhibitory than norfloxacin alone, and the combination showed antagonistic activity. The inhibitory activities of antibiotics ranked as norfloxacin > norfloxacin + lomefloxacin > lomefloxacin. Although the simulated experimental conditions did not fully match the actual water condition, the above results implied that combination antibiotics have antagonistic effects on the denitrification process. Such effects were related largely to the microbial numbers and activities, activities of denitrification enzymes, as well as abundance variations of dominant denitrifying bacteria Achromobacter xylosoxidans, Acinetobacter baumannii, and Pseudomonas sp. KY and the nosZ and aac genes. As reaction time increased, the denitrifying bacteria gradually adapted to the environment of low-level antibiotics and the number of quinolone resistance genes increased; also on the rise were the amount and activities of denitrifying bacteria, activities of denitrification enzymes, and microbial communities.