Lu Lingeng, Hume Michael E, Sternes Keith L, Pillai Suresh D
Poultry Science Department, Food Safety and Environmental Microbiology Program, Texas A&M University, Kleberg Center, 2472 TAMUS, 418D Kleberg, College Station, TX 77843-2472, USA.
Water Res. 2004 Nov;38(18):3899-908. doi: 10.1016/j.watres.2004.06.020.
Identifying the sources of fecal contaminants in surface water bodies such as rivers and lakes is of significant importance for environmental quality, food safety and regulatory purposes. Current DNA library-based source tracking approaches rely on the comparison of the genetic relatedness among the fecal contaminants. The objective of this study was to determine the genetic relatedness of Escherichia coli isolated from irrigation water and associated sediments using pulse field gel electrophoresis (PFGE) and to evaluate the genetic stability of the E. coli PFGE patterns. The isolates were obtained over a 4-month period from specific locations within irrigation canals and sediments associated with the Rio Grande River along the Texas-Mexico border. Fifty E. coli isolates were genotyped using PFGE. Different E. coli genotypes were identified among samples collected in 11 different locations. Some isolates obtained over successive months showed similar genotypic patterns. In the laboratory experiment, the PFGE pattern of one E. coli strain changed during survival in irrigation water. The genetic relatedness of this strain changed from >95% to <83% over 8-week survival. These results imply that PFGE is of such extreme resolution that it may be a challenging task to rely solely on a PFGE-based source tracking DNA fingerprint library for large watersheds.
识别河流和湖泊等地表水体中粪便污染物的来源对于环境质量、食品安全和监管目的具有重要意义。当前基于DNA文库的源追踪方法依赖于粪便污染物之间遗传相关性的比较。本研究的目的是使用脉冲场凝胶电泳（PFGE）确定从灌溉水及相关沉积物中分离出的大肠杆菌的遗传相关性，并评估大肠杆菌PFGE图谱的遗传稳定性。这些分离株是在4个月的时间里从灌溉渠内的特定位置以及与德克萨斯州 - 墨西哥边境的格兰德河相关的沉积物中获得的。使用PFGE对50株大肠杆菌分离株进行基因分型。在11个不同地点采集的样本中鉴定出了不同的大肠杆菌基因型。连续数月获得的一些分离株显示出相似的基因型模式。在实验室实验中，一株大肠杆菌在灌溉水中存活期间PFGE图谱发生了变化。在8周的存活期内，该菌株的遗传相关性从>95%变为<83%。这些结果表明，PFGE具有极高的分辨率，以至于仅依靠基于PFGE的源追踪DNA指纹文库来研究大型流域可能是一项具有挑战性的任务。
