title: Clonal populations of thermotolerant Enterobacteriaceae in recreational water and their potential interference with fecal Escherichia coli counts.
abstract: Bacterial strains were isolated from beach water samples using the original Environmental Protection Agency method for Escherichia coli enumeration and analyzed by pulsed-field gel electrophoresis (PFGE). Identical PFGE patterns were found for numerous isolates from 4 of the 9 days sampled, suggesting environmental replication. 16S rRNA gene sequencing, API 20E biochemical testing, and the absence of beta-glucuronidase activity revealed that these clonal isolates were Klebsiella, Citrobacter, and Enterobacter spp. In contrast, 82% of the nonclonal isolates from water samples were confirmed to be E. coli, and 16% were identified as other fecal coliforms. These nonclonal isolates produced a diverse range of PFGE patterns similar to those of isolates obtained directly from untreated sewage and gull droppings. beta-Glucuronidase activity was critical in distinguishing E. coli from other fecal coliforms, particularly for the clonal isolates. These findings demonstrate that E. coli is a better indicator of fecal pollution than fecal coliforms, which may replicate in the environment and falsely elevate indicator organism levels.
authors.affiliation: Great Lakes WATER Institute, University of Wisconsin-Milwaukee, Milwaukee, Wisconsin 53204, USA. mclellan@uwm.edu
authors.forename: S L
authors.initials: SL
authors.lastname: McLellan
authors.forename: A D
authors.initials: AD
authors.lastname: Daniels
authors.forename: A K
authors.initials: AK
authors.lastname: Salmore
mesh_terms: D000818:Animals; D015169:Colony Count, Microbial; D016521:Electrophoresis, Gel, Pulsed-Field; D004755:Enterobacteriaceae / Q000235:genetics / Q000302:isolation & purification*; D004784:Environmental Monitoring / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification*; D005618:Fresh Water / Q000382:microbiology*; D006801:Humans; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D011998:Recreation; D014481:United States; D014484:United States Environmental Protection Agency / Q000592:standards; D014876:Water Pollution
chemical_list: D012336:RNA, Ribosomal, 16S