Segura Pedro A, Saadi Karim, Clair Alexandra, Lecours Marc-André, Yargeau Viviane
Department of Chemistry, Université de Sherbrooke, 2500 boulevard de l'Université, Sherbrooke, QC, Canada J1K 2R1 E-mail:
Department of Chemical Engineering, McGill University, 3610 University, Montreal, QC, Canada H3A 0C5.
Water Sci Technol. 2015;72(9):1578-87. doi: 10.2166/wst.2015.369.
We studied the nature and antimicrobial activity of ozonolysis transformation products (OTPs) of levofloxacin (LEV), a frequently detected fluoroquinolone antimicrobial in environmental waters. Two bioassays, the Kirby-Bauer test and the broth microdilution assay, were used to measure changes in the antimicrobial activity of solutions at low LEV to O3 molar ratios (2:1, 2:3 and 1:3) compared to solutions without added O3 (LEV:O3 1:0). The Kirby-Bauer test was not sensitive enough to detect significant differences in the growth inhibition zones in samples LEV:O3 2:1 and LEV:O3 1:0; however, the broth microdilution assay showed that bacterial growth inhibition was significantly lower (P<0.001) in the solutions exposed to O3. Loss of antimicrobial activity in LEV:O3 2:1 solutions of (48±16)% was in agreement with the concentration decrease of LEV of (36±3)% in those same samples. A method of identification of OTPs using XCMS Online was applied to LEV:O3 2:1 and 1:0 samples and indicated the presence of an OTP of LEV of formula C18H20O5N3F, which was identified as LEV-N-oxide. The molecular structure of this compound was partially confirmed by tandem mass spectrometry experiments. This study showed that even at sub-optimal ozone doses, OTPs of higher antimicrobial activity than LEV were not formed.
我们研究了左氧氟沙星（LEV）的臭氧分解转化产物（OTPs）的性质和抗菌活性，LEV是环境水体中经常检测到的氟喹诺酮类抗菌剂。使用两种生物测定方法，即 Kirby-Bauer 试验和肉汤微量稀释试验，来测量与未添加 O3 的溶液（LEV:O3 1:0）相比，低 LEV 与 O3 摩尔比（2:1、2:3 和 1:3）的溶液中抗菌活性的变化。Kirby-Bauer 试验不够灵敏，无法检测到 LEV:O3 2:1 和 LEV:O3 1:0 样品中生长抑制圈的显著差异；然而，肉汤微量稀释试验表明，暴露于 O3 的溶液中细菌生长抑制显著降低（P<0.001）。LEV:O3 2:1 溶液中抗菌活性损失（48±16）%与这些相同样品中 LEV 浓度降低（36±3）%一致。使用 XCMS Online 鉴定 OTPs 的方法应用于 LEV:O3 2:1 和 1:0 样品，表明存在分子式为 C18H20O5N3F 的 LEV 的 OTP，其被鉴定为 LEV-N-氧化物。该化合物的分子结构通过串联质谱实验得到部分证实。本研究表明，即使在次优臭氧剂量下，也不会形成抗菌活性高于 LEV 的 OTPs。
