Division of Microbiology, National Center for Toxicological Research, Jefferson, AR, USA.
Curr Microbiol. 2012 Jan;64(1):60-5. doi: 10.1007/s00284-011-0020-4. Epub 2011 Oct 18.
Daidzein (4',7-dihydroxyisoflavone), a phytoestrogen found in soybeans mainly in the form of its glycoside daidzin, is metabolized by colonic bacteria to compounds with altered estrogenic activities, which may affect human health. Antibacterial agents used for the treatment of infections can alter the composition of bacterial populations in the colon and therefore can affect daidzein metabolism. To rapidly detect the effects of different concentrations of antibiotics on daidzein metabolism by colonic bacteria of monkeys and identify the subpopulation involved in daidzein metabolism, Etest strips containing antibacterial agents from three classes (tetracyclines, fluoroquinolones, and β-lactams) were used to eliminate the colonic bacteria that were susceptible to 0-32 μg/ml of each antibacterial agent and test the surviving bacteria for their ability to metabolize daidzein. The metabolism of daidzein by the colonic microflora was measured before and after the colonic bacterial population was exposed to antibacterial agents. The metabolites were detected by high performance liquid chromatography and mass spectrometry after incubation of the cultures for various times. Exposure of colonic microflora to antibiotics had various effects on daidzein metabolism. Tetracycline completely removed the bacteria metabolizing daidzein, metabolism of daidzein was not changed in cultures of bacteria after ceftriaxone treatment, and ciprofloxacin enriched for the bacteria metabolizing daidzein. In liquid cultures treated with various concentrations of ciprofloxacin, 4 μg/ml of ciprofloxacin favored the growth of bacteria that metabolized daidzein. This is the first time in which the Etest has been used to show that, whereas some antibiotics eliminate phytoestrogen-metabolizing bacteria in colonic microflora, others enrich them by eliminating the non-metabolizing strains in the population.
大豆苷元（4'，7-二羟基异黄酮）是一种植物雌激素，主要以大豆苷的形式存在于大豆中，它可被结肠细菌代谢为具有改变的雌激素活性的化合物，这可能会影响人类健康。用于治疗感染的抗菌药物会改变结肠细菌种群的组成，从而影响大豆苷元的代谢。为了快速检测不同浓度的抗生素对猴子结肠细菌代谢大豆苷元的影响，并确定参与大豆苷元代谢的亚群，使用了含有来自三类抗菌药物（四环素类、氟喹诺酮类和β-内酰胺类）的 Etest 条来消除对每种抗菌药物 0-32μg/ml 敏感的结肠细菌，并测试存活细菌代谢大豆苷元的能力。在将结肠细菌暴露于抗菌药物之前和之后，测量结肠微生物区系对大豆苷元的代谢。在孵育培养物不同时间后，通过高效液相色谱和质谱法检测代谢物。抗生素暴露于结肠微生物区系对大豆苷元代谢有不同的影响。四环素完全去除了代谢大豆苷元的细菌，头孢曲松处理后的细菌培养物中大豆苷元的代谢没有改变，环丙沙星富集了代谢大豆苷元的细菌。在用不同浓度环丙沙星处理的液体培养物中，4μg/ml 的环丙沙星有利于代谢大豆苷元的细菌生长。这是首次使用 Etest 显示，虽然一些抗生素消除了结肠微生物区系中植物雌激素代谢细菌，但其他抗生素通过消除种群中的非代谢菌株来富集它们。
