Division of Microbiology, National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR 72079-9502, USA.
Regul Toxicol Pharmacol. 2012 Feb;62(1):74-84. doi: 10.1016/j.yrtph.2011.11.013. Epub 2011 Dec 9.
Most antibiotic inactivation studies have been conducted through in vitro incubations of human use aminoglycosides, beta-lactams, and fluoroquinolones, usually at fecal concentrations expected with therapeutic dose regimens in humans and animals. Less is known about the inactivation of these molecules when ingested at concentrations consistent with residue levels present in animal-derived foods from antibiotic treated animals. In this investigation, we used the fluoroquinolone, enrofloxacin which is specifically marketed for veterinary medicine as test compound. Fecal suspensions at 10%, 25%, and 50% (w/v) were subjected to physicochemical and molecular characterization and used in the drug binding studies. The fecal binding of enrofloxacin added at concentrations of 0.06, 0.1, 1, 5, 15, 50, and 150 mg/L was determined in various fecal slurry suspensions using analytical chemistry and microbiological assay methods. There was consistent correlation between both assay methods. By the analytical chemistry assay, the 10%, 25% and 50% diluted autoclaved fecal samples dosed with enrofloxacin showed binding of 50±4.6%, 54±6.5% and 56±6.8% of the enrofloxacin, respectively. Binding of enrofloxacin to fecal contents occurred rapidly within 10 min and remained constant over the incubation period. Denaturing gradient gel electrophoreses and pyrosequencing analysis showed varied profiles of the bacterial composition of the human intestinal microbiota for fecal samples from different individuals. This study provided information on methodological questions that have concerned regulatory authorities on in vitro testing to determine if concentrations of veterinary antimicrobial agent residues entering the human colon remain microbiologically active.
大多数抗生素失活动力学研究都是通过体外孵育人用氨基糖苷类、β-内酰胺类和氟喹诺酮类抗生素进行的，通常使用的是与人用和动物治疗剂量方案一致的粪便浓度。对于在摄入浓度与来自经抗生素处理动物的动物源性食品中存在的残留水平一致的情况下这些分子的失活情况，人们了解较少。在这项研究中，我们使用了氟喹诺酮恩诺沙星作为测试化合物，它专门用于兽医。将浓度为 10%、25%和 50%（w/v）的粪便悬浮液进行物理化学和分子特征分析，并用于药物结合研究。在各种粪便悬浮液中，使用分析化学和微生物测定方法测定了浓度为 0.06、0.1、1、5、15、50 和 150mg/L 的恩诺沙星的粪便添加物的结合情况。两种测定方法之间存在一致的相关性。通过分析化学测定法，用恩诺沙星处理的 10%、25%和 50%稀释的高压灭菌粪便样本显示，恩诺沙星的结合率分别为 50±4.6%、54±6.5%和 56±6.8%。恩诺沙星与粪便内容物的结合在 10 分钟内迅速发生，并在孵育期间保持恒定。变性梯度凝胶电泳和焦磷酸测序分析显示，不同个体的粪便样本的人类肠道微生物群的细菌组成存在不同的图谱。本研究提供了有关监管机构关注的体外测试方法学问题的信息，以确定进入人类结肠的兽医抗菌剂残留的浓度是否仍然具有微生物学活性。
