Posted: November 1st, 2009 - 9:20pm

Abstract:
This study aimed to assess the importance of quantitatively detecting Campylobacter spp. in environmental surface water. The prevalence and the quantity of Campylobacter spp., thermotolerant coliforms, and Escherichia coli in 2,471 samples collected weekly, over a 2-year period, from 13 rivers and 12 streams in the Eastern Townships, Quebec, Canada, were determined. Overall, 1,071 (43%), 1,481 (60%), and 1,463 (59%) samples were positive for Campylobacter spp., thermotolerant coliforms, and E. coli, respectively. There were weak correlations between the weekly distributions of Campylobacter spp. and thermotolerant coliforms (Spearman’s coefficient = 0.27; P = 0.008) and between the quantitative levels of the two classes of organisms (Kendall tau-b correlation coefficient = 0.233; P < 0.0001). Well water samples from the Eastern Townships were also tested. Five (10%) of 53 samples from private surface wells were positive for Campylobacter jejuni, of which only 2 were positive for thermotolerant coliforms.
These findings suggest that microbial monitoring of raw water by using only fecal indicator organisms is not sufficient for assessing the occurrence or the load of thermophilic Campylobacter spp. Insights into the role of environmental water as sources for sporadic Campylobacter infection will require genus-specific monitoring techniques.
Snips from Discussion:
Although acute point source outbreaks involving poultry as well as water contamination are well described, the majority of cases represent sporadic disease with no clear source. The standard methods for assessing water quality rely on the detection of thermotolerant coliforms and E. coli. Direct assays for Campylobacter spp. are not commonly used in public health surveys on the assumption that coliforms represent an adequate surrogate for contamination with enteric pathogens. Our comprehensive analysis of over 2,400 environmental water samples collected weekly over 2 years indicates this is an incorrect assumption and suggests that deciphering the sources for sporadic cases of campylobacteriosis will require genus-specific techniques.
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It is plausible that the presence of Campylobacter spp. Correlates with fecal indicator organisms after adjusting for confounding factors (e.g., location, season, rainfall, and agricultural practice). However, environmental laboratories do not consider such factors when describing water quality but rather focus on thermotolerant coliform counts to assess the safety of untreated water used for drinking or recreational purposes.
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Public health authorities use the presence of E. coli as a surrogate for the presence of Campylobacter spp., although it is inappropriate to use an organism as an indicator of another if it does not behave in a similar way.
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We conclude that the presence or absence of thermophilic Campylobacter cannot be inferred from the results of monitoring of raw water using fecal indicator organisms or turbidity.
The poor correlation between the thermophilic Campylobacter and coliforms in natural waters likely reflects multiple factors. Dorner et al. observed that Campylobacter levels in the Grand River watershed, Ontario, Canada, frequently peaked before coliforms and turbidity and then become undetectable sooner (16). This pattern suggests that Campylobacter spp. and potentially other pathogens are in limited supply and are flushed out of the stream before the coliform bacteria.
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In reevaluating contaminated water supplies as a source of sporadic cases of Campylobacter sp. infection, it is important to consider the pathogenesis of these infections. In human volunteer studies Campylobacter spp. demonstrate a classic sigmoid dose-response curve, with an estimated 50% infectious dose of _800 organisms (5, 34, 44). The probability of contracting infection following exposure to one Campylobacter sp. organism has been estimated to be _1 in 150 (36). However, the dose-response relation has been recently updated based on two outbreaks of infection due to raw milk in children, resulting in higher (_36-fold) probabilities of infection at low doses than previously estimated (45). Thus, at least for some strains of Campylobacter spp., ingestion of water or food containing even very small numbers of organisms may be a potential health hazard, suggesting that sensitive methods are needed to evaluate environmental and drinking water sources. Large numbers of people being exposed to low doses will also result in significant levels of disease.
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