Citation:

WALTERS, S. P., O. C. SHANKS, C. T. NIETCH, V. P. GANNON, AND K. G. FIELD. DYNAMICS OF AQUATIC FECAL CONTAMINATION, FECAL SOURCE IDENTIFICATION, AND CORRELATION OF BACTEROIDALES HOST-SPECIFIC MARKERS DETECTION WITH FECAL PATHOGENS. Presented at 13th Ocean Sciences Meeting, Honolulu, UNITED STATES MINOR OUTLYING ISLANDS, February 20 - 24, 2006.

Impact/Purpose:

To inform the public.

Description:

Fecal pollution impairs the health and productivity of coastal waters and causes human disease. PCR of host-specific 16S rDNA sequences from anaerobic Bacteroidales bacteria offers a promising method of tracking fecal contamination and identifying its source(s). Before Bacteroidales host-specific markers can be used to assess human health risks it is important to know how detection of the markers correlates with the presence of human pathogens and how long the marker organisms survive relative to pathogens, standard indicators, and environmental changes. We correlated Bacteroidales molecular markers with standard fecal indicator bacteria and environmental conditions in samples collected over a two-year period from Tillamook Bay and five tributaries within the Tillamook River Basin. We performed Bacteroidales PCR assays using host-specific primers for fecal source identification, and recorded E. coli MPN, temperature, turbidity, and 5-day precipitation. In samples near point sources of fecal contamination we found close correlation between E. coli MPN and detection of Bacteroidales markers. Climate and water quality data suggested a rainfall-runoff model for microbial source loading, mirroring the annual precipitation cycle, and compared to humans, ruminants were a more significant source of fecal input. Two anomalies arose from this dataset. In rivers, E. coli counts increased over summer months, while the probability of detecting Bacteroidales markers fell to a minimum from April to July, increasing in the fall. In the bay, Bacteroidales markers were detected at high levels, but this was not reflected in E. coli MPN. In a separate 3 year study, we tested 437 water samples for Bacteroidales host-specific molecular markers, and for presence of E. coli O157:H7, Salmonella spp., and Campylobacter. The odds of detecting E. coli O157:H7 and Salmonella spp. were significantly higher when ruminant-specific markers were present. Detection of the human-specific markers did not correlate with the presence of E. coli O157:H7 or Salmonella; however, the odds of Campylobacter being present were 4 times greater when human-specific markers were detected. These two studies demonstrate that Bacteroidales host-specific markers are detected when human pathogens are present, and support their application in assessing human health risk.

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