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Faecal contamination source identification using a combination of chemical and microbial biomarkers
Expanded Title:The aims of this work were to (a) review detection methods for faecal contamination and its sources, and (b) to select appropriate analytical methods for sediment and water samples. In the review, it is noted that (a) the traditional indicators of faecal coliforms and E. coli do not allow source identification and that (b) natural environmental concentrations can also confound interpretation as these are not of faecal origin. The ratio of faecal coliforms to faecal streptococci has also been proposed as a possible source-tracking indicator but has been shown to be unreliable. The majority of research on identifying the sources of faecal contamination in South African water resources has been done using viral biomarkers. These are bacteriophages (viruses that infect bacteria) and specifically coliphages (which infect E. coli). However, various shortcomings prevent these from being used effectively either as indicators of faecal contamination or of the sources of the contamination. Bifidobacteria have also been used for faecal source tracking. In particular, the “tracking ratio” of the sorbitol-fermenting bifidobacteria to total bifidobacteria concentrations (CFU/100 mL) has been used with values >0.2 suggesting a human source and values <0.05 suggesting an animal source. However, these threshold values are not universal and so need to be established in each area. Rhodococcus coprophilus can also be used to indicate a faecal contamination source as this bacterium is only found in animal faeces, not humans. Most literature on chemical biomarkers of faecal pollution has focused on cholesterol metabolites (sterols). To investigate faecal source tracking methods, 7 sites were chosen because they had “permanent” faecal contamination, on the basis of them having non-zero faecal coliform and E. coli concentrations and a positive H2S strip test on 3 separate occasions. Bifidobacteria-based tracking ratios were obtained for the 7 sites with mostly new samples. However, threshold values were not evident. The sites were therefore re-sampled and the concentrations of bifidobacteria re-measured using different culture media. Again threshold values were not evident. Furthermore, discrepancies were evident in that some sorbitol-fermenting bifidobacteria concentrations were greater than the total bifidobacteria concentrations. Ultimately, this study was unsuccessful in its attempt to develop a practical faecal source tracking method based on either bifidobacteria or sterols for use in South Africa. Nevertheless, the work presents a useful review of source tracking knowledge and a better understanding of some the difficulties involved.
Date Published:01/04/2012
Document Type:Research Report
Document Keywords:Health, Technology, Water Quality
Document Format:Report
Document File Type:pdf
Research Report Type:Consultant
WRC Report No:KV 295/12
ISBN No:978-1-4312- 0264-5
Authors:Tandlich R; Luyt CD; Muller WJ
Project No:K8/806
Organizations:Division of Pharmaceutical Chemistry, Faculty of Pharmacy, Rhodes University; Unilever Centre for Environmental Water Quality Institute for Water Research Rhodes University
Document Size:2 052 KB
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