title: Microbial source tracking in a small southern California urban watershed indicates wild animals and growth as the source of fecal bacteria.
abstract: Three independent microbial source tracking (MST) methods were applied to a small urban subwatershed in Orange County, California. Fifty-seven water samples collected over summer 2002 were analyzed for human adenovirus and enterovirus. Enterococci and E. coli were isolated for antibiotic resistance analysis (ARA) and for PCR identification of human- and animal-specific toxin genes, respectively. All water samples were PCR negative for human enteroviruses and E. coli human-specific toxin gene. E. coli toxin markers revealed the presence of toxin genes specific to bird, rabbit, and cow. Enterococci ARA results supported this conclusion and indicated that fecal bacteria from bird and wild animal feces as well as soil were the predominant source found in the watershed. An E. coli, isolated from the watershed and inoculated back into the heat-sterilized storm drain water, increased 4 log units within 6 days. Collectively, these results suggest that bird and wild animal feces, soil amendments, and/or fecal coliform growth in the storm drain are the major contributors to the fecal bacterial pollution in downstream areas. However, human adenoviruses were detected on two occasions. Fecal bacterial concentrations were not elevated on these two occasions, suggesting that the elevated levels of fecal indicator bacteria in this small watershed could be unrelated to the source of human adenovirus.
authors.affiliation: Civil and Environmental Engineering, University of California, Irvine, CA 92697, USA. sjiang@uci.edu
authors.forename: Sunny C
authors.initials: SC
authors.lastname: Jiang
authors.forename: Weiping
authors.initials: W
authors.lastname: Chu
authors.forename: Betty H
authors.initials: BH
authors.lastname: Olson
authors.forename: Jian-Wen
authors.initials: JW
authors.lastname: He
authors.forename: Samuel
authors.initials: S
authors.lastname: Choi
authors.forename: Jenny
authors.initials: J
authors.lastname: Zhang
authors.forename: Joanne Y
authors.initials: JY
authors.lastname: Le
authors.forename: Phillip B
authors.initials: PB
authors.lastname: Gedalanga
mesh_terms: D000256:Adenoviridae / Q000235:genetics / Q000302:isolation & purification*; D000818:Animals; D000835:Animals, Wild / Q000382:microbiology*; D001427:Bacterial Toxins / Q000302:isolation & purification*; D002140:California; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D016002:Discriminant Analysis; D024881:Drug Resistance, Bacterial; D004784:Environmental Monitoring / Q000379:methods*; D004926:Escherichia coli / Q000235:genetics / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D006801:Humans; D016133:Polymerase Chain Reaction; D014505:Urban Population; D014871:Water Microbiology
chemical_list: D001427:Bacterial Toxins; D004269:DNA, Bacterial; D004279:DNA, Viral