Investigation of an Escherichia coli environmental benchmark for waterborne pathogens in agricultural watersheds in Canada

Canada's National Agri-Environmental Standards Initiative sought to develop an environmental benchmark for low-level waterborne pathogen occurrence in agricultural watersheds. A field study collected 902 water samples from 27 sites in four intensive agricultural watersheds across Canada from 2005 to 2007. Four of the sites were selected as reference sites away from livestock and human fecal pollution sources in each watershed. Water samples were analyzed for Campylobacter spp., Salmonella spp., Escherichia coli O157:H7, Cryptosporidium spp., Giardia spp., and the water quality indicator E. coli. The annual mean number of pathogen species was higher at agricultural sites (1.54 ± 0.07 species per water sample) than at reference sites (0.75 ± 0.14 species per water sample). The annual mean concentration of E. coli was also higher at agricultural sites (491 ± 96 colony-forming units [cfu] 100 mL(-1)) than at reference sites (53 ± 18 cfu 100 mL(-1)). The feasibility of adopting existing E. coli water quality guideline values as an environmental benchmark was assessed, but waterborne pathogens were detected at agricultural sites in 80% of water samples with low E. coli concentrations (<100 cfu 100 mL(-1)). Instead, an approach was developed based on using the natural background occurrence of pathogens at reference sites in agricultural watersheds to derive provisional environmental benchmarks for pathogens at agricultural sites. The environmental benchmarks that were derived were found to represent E. coli values lower than geometric mean values typically found in recreational water quality guidelines. Additional research is needed to investigate environmental benchmarks for waterborne pathogens within the context of the "One World, One Health" perspective for protecting human, domestic animal, and wildlife health.

Incidence of Legionella organisms in selected Ontario (Canada) cities

The distribution of Legionella pneumophila in water inside buildings was examined by means of culture methods. Cooling tower sumps and condenser valves harboured the organism at the highest frequency and in the highest concentrations. The bacterium was also frequently isolated from potable water systems, including hot and cold mixed taps, drinking water fountains and showers. When water quality parameters were examined, only elevated pH, total particulate nitrogen and alkalinity were correlated with the occurrence of L. pneumophila. Survival of the organism in water was increased at slightly basic pH and lower temperatures. The proliferation of the organism in water within buildings is probably due to a number of interrelated environmental factors that influence its survival and growth.

Microbiological water and effluent sample preservation

A study, using four types of water samples ranging from relatively pure stream water to water containing industrial and domestic effluents, was carried out to investigate the effect of storage temperature on four bacterial parameters: total coliform, fecal coliform, fecal streptococcus, and heterotrophic bacteria. In the study, each water sample was cooled immediately after collection to approximately 1.5 degrees C by storage in crushed ice. At 2-, 24-, 30-, and 48-h intervals, the sample was mixed, and a subsample was removed and tested. Three separate analyses for each parameter were made on each subsample. The data available for statistical analyses contained, in some cases, the values obtained for the three subsamples and, in others, the means of the three values. The data were analysed as replicated data and as part of the entire set. The analysed data indicated (i) that with the exception of heterotrophic populations, more than 75% of the samples were microbiologically stable for at least 24 h, (ii) that at least 50% of samples tested for heterotrophic densities were stable for a minimum period of 24 h, (iii) that the original water temperature and bacterial load do not appear to be consistent factors in the preservation of samples for microbiological analysis, and (iv) that nutrient levels, also, do not seem to be consistent factors in the preservation of water samples for microbiological analyses.

Relationship between various bacterial populations and coprostanol and cholesterol

A year-long study was conducted at three different locations in Canada to evaluate the relationship between fecal sterols and bacterial populations. A statistical model was constructed to study the following: (i) seasonal variations in the sterols and bacterial parameters; (ii) the differences between morning and afternoon samples; (iii) the relationship between the two sterols (coprostanol and cholesterol) as well as their relationship to the bacterial parameters; and (iv) the geographical differences between the three sampling sites. Application of the model to the data indicated that (i) the relationship in receiving waters between coprostanol and cholesterol was found to be highly significant; (ii) at two sampling sites the relationship between fecal sterols and fecal coliforms was positively significant at the 5% level; (iii) at one sampling site there was a positive relationship between fecal sterols and the fecal coliform - fecal streptococcus ratio; and (iv) in a.m. vs. p.m. samples significant differences were noted in coliform, fecal coliform, and fecal streptococcus densities while no significant differences were found in heterotroph densities and coprostanol and cholesterol levels. Raw and treated sewage from four sewage-treatment plants were also studied to provide baseline control data. Data support the conclusion that while no consistent relationship exists between bacterial parameters and fecal sterols, fecal sterols could be considered as unequivocal indicators of the presence of fecal material in water.