Ishii Satoshi, Hansen Dennis L, Hicks Randall E, Sadowsky Michael J
Department of Soil, Water, and Climate, Center for Microbial and Plant Genomics, and BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108, USA.
Environ Sci Technol. 2007 Apr 1;41(7):2203-9. doi: 10.1021/es0623156.
The Duluth Boat Club (DBC) Beach, located in the Duluth-Superior harbor of Lake Superior, is frequently closed in summer due to high counts of Escherichia coli, an indicator of fecal contamination. However, the sources of bacteria contributing to beach closure are currently unknown. In this study, we investigated the potential sources of E. coli contaminating the DBC beach by using modified rep-PCR (HFERP) DNA fingerprinting. Over 3600 E. coli strains were obtained from 55 lake water, 25 sediment, and 135 sand samples taken from five transects at the DBC beach at 11 different times during the summer through fall months of 2004 and 2005. Potential sources of E. coli at this beach were determined by using a known-source DNA fingerprint library containing unique E. coli isolates from wildlife, waterfowl, and treated wastewater obtained near Duluth, MN. Amounts E. coli in the samples were enumerated by membrane filtration counting, and the presence of potentially pathogenic E. coli was determined by using multiplex PCR. E. coli counts in all samples increased during the summer and early fall (Julyto September). While E. coli in spring samples originated mainly from treated wastewater effluent, the percentage of E. coli from waterfowl increased from summer to fall. DNA fingerprint analyses indicated that some E. coli strains may be naturalized, and autochthonous members of the microbial community in the beach sand and sediments were examined. However, multiplex PCR results indicated that <1% of the E. coli strains at the DBC was potentially pathogenic. Our results also suggest that wave action may influence the early colonization and homogeneous distribution of E. coli in beach sand and the subsequent release of sand or sediment-borne E. coli into lake water. Taken together, these results indicate that sand and sediment serve as temporal sources and sinks of human and waterfowl-derived E. coli that contribute to beach closures.
德卢斯船艇俱乐部（DBC）海滩位于苏必利尔湖的德卢斯 - 苏必利尔港，由于大肠杆菌数量过多（粪便污染的一个指标），在夏季经常关闭。然而，导致海滩关闭的细菌来源目前尚不清楚。在本研究中，我们使用改良的重复聚合酶链反应（HFERP）DNA指纹技术调查了污染DBC海滩的大肠杆菌的潜在来源。在2004年和2005年夏季至秋季的11个不同时间，从DBC海滩的五个断面采集了55份湖水、25份沉积物和135份沙子样本，共获得3600多株大肠杆菌菌株。通过使用一个已知来源的DNA指纹文库来确定该海滩大肠杆菌的潜在来源，该文库包含从明尼苏达州德卢斯附近获得的野生动物、水禽和处理后废水中独特的大肠杆菌分离株。通过膜过滤计数法对样本中的大肠杆菌数量进行计数，并使用多重聚合酶链反应确定潜在致病性大肠杆菌的存在。所有样本中的大肠杆菌数量在夏季和初秋（7月至9月）有所增加。虽然春季样本中的大肠杆菌主要来自处理后的废水排放，但从夏季到秋季，来自水禽的大肠杆菌百分比有所增加。DNA指纹分析表明，一些大肠杆菌菌株可能已归化，并对海滩沙子和沉积物中微生物群落的本地成员进行了检查。然而，多重聚合酶链反应结果表明，DBC海滩上<1%的大肠杆菌菌株具有潜在致病性。我们的结果还表明，波浪作用可能会影响大肠杆菌在海滩沙子中的早期定殖和均匀分布，以及随后沙子或沉积物携带的大肠杆菌向湖水中的释放。综上所述，这些结果表明，沙子和沉积物是导致海滩关闭的人类和水禽来源大肠杆菌的临时来源和汇。
