Department of Civil & Environmental Engineering, Stanford University, Stanford, CA 94305, USA.
J Appl Microbiol. 2009 Nov;107(5):1740-50. doi: 10.1111/j.1365-2672.2009.04440.x. Epub 2009 Jun 5.
The absence of standardized methods for quantifying faecal indicator bacteria (FIB) in sand hinders comparison of results across studies. The purpose of the study was to compare methods for extraction of faecal bacteria from sands and recommend a standardized extraction technique.
Twenty-two methods of extracting enterococci and Escherichia coli from sand were evaluated, including multiple permutations of hand shaking, mechanical shaking, blending, sonication, number of rinses, settling time, eluant-to-sand ratio, eluant composition, prefiltration and type of decantation. Tests were performed on sands from California, Florida and Lake Michigan. Most extraction parameters did not significantly affect bacterial enumeration. anova revealed significant effects of eluant composition and blending; with both sodium metaphosphate buffer and blending producing reduced counts.
The simplest extraction method that produced the highest FIB recoveries consisted of 2 min of hand shaking in phosphate-buffered saline or deionized water, a 30-s settling time, one-rinse step and a 10 : 1 eluant volume to sand weight ratio. This result was consistent across the sand compositions tested in this study but could vary for other sand types.
Method standardization will improve the understanding of how sands affect surface water quality.
沙中粪性指示菌（FIB）量化方法缺乏标准化，这阻碍了研究结果的比较。本研究旨在比较从沙中提取粪细菌的方法，并推荐一种标准化的提取技术。
评估了 22 种从沙中提取肠球菌和大肠杆菌的方法，包括手振、机械振、搅拌、超声、冲洗次数、沉降时间、洗脱液-砂比、洗脱液成分、预过滤和沉降方式的多种组合。测试在加利福尼亚、佛罗里达和密歇根湖的沙中进行。大多数提取参数对细菌计数没有显著影响。方差分析显示洗脱液成分和搅拌有显著影响；偏磷酸钠缓冲液和搅拌均导致计数减少。
产生最高 FIB 回收率的最简单提取方法包括在磷酸盐缓冲液或去离子水中手振 2 分钟，沉降 30 秒，冲洗一次，洗脱液体积与砂重比为 10:1。本研究测试的沙成分结果一致，但对于其他沙类型可能会有所不同。
方法标准化将提高对沙如何影响地表水质量的理解。
