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This study examined the distribution of antibiotic resistant Escherichia coli and E. coli O157 isolated from water, sediment and biofilms in an intensive agricultural watershed (Elk Creek, British Columbia) between 2005 and 2007. It also examined physical and chemical water parameters associated with antibiotic resistance. Broth microdilution techniques were used to determine minimum inhibitory concentrations (MIC) for E. coli (n=214) and E. coli O157 (n=27) recovered isolates for ampicillin, cefotaxime, ciprofloxacin, nalidixic acid, streptomycin and tetracycline. Both E. coli and E. coli O157 isolates showed highest frequency of resistance to tetracycline, ampicillin, streptomycin and nalidixic acid; respectively. For E. coli, the highest frequency of resistance was observed at the most agriculturally-impacted site, while the lowest frequency of resistance was found at the headwaters. Sediment and river rock biofilms were the most likely to be associated with resistant E. coli, while water was the least likely. While seasonality (wet versus dry) had no relationship with resistance frequency, length of biofilm colonization of the substratum in the aquatic environment only affected resistance frequency to nalidixic acid and tetracycline. Multivariate logistic regressions showed that water depth, nutrient concentrations, temperature, dissolved oxygen and salinity had statistically significant associations with frequency of E. coli resistance to nalidixic acid, streptomycin, ampicillin and tetracycline. The results indicate that antibiotic resistant E. coli and E. coli O157 were prevalent in an agricultural stream. Since E. coli is adept at horizontal gene transfer and prevalent in biofilms and sediment, where ample opportunities for genetic exchange with potential environmental pathogens present themselves, resistant isolates may present a risk to ecosystem, wildlife and public health., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Despite its relevance to public health, presence and concentrations of Campylobacter spp. in biofilms in natural aquatic environments has not been investigated. This study examined the occurrence of Campylobacter spp. in biofilms on a variety of surfaces (river rock, slate rock, wood, Lexan™, sandpaper, and sediment) and in water from December 2005 to December 2006 to find a substratum that facilitated campylobacters detection in natural aquatic environments. Samples were collected at four sites in an agricultural watershed (Elk Creek, British Columbia). Campylobacter spp. presence was determined using culturing methods. Correlations between chemical, physical and microbiological water quality parameters and Campylobacter spp. distribution on different surface types were also investigated. Campylobacter spp. had a prevalence of 13% in the wet season, but was not recovered in the dry season. Its prevalence was highest in sediment (27%), followed by slate rock (22%), Lexan and wood (13%), river rock (9%) and water (8%), respectively. No Campylobacter spp. was found in sandpaper biofilms. Several other criteria were used to assess substrata effectiveness, such as correlation amongst Campylobacter spp., indicator bacteria and water quality parameters, cost and availability of substratum, potential for standardizing substratum, ease of biofilm removal and probability of substratum loss in situ. Results show that sediment, slate rock or wood could be used as substrata for Campylobacter spp. monitoring. The study also highlights the potential use of nitrates and enterococci as faecal contamination indicators to protect public health., (Copyright © 2011 Elsevier GmbH. All rights reserved.)