Antimicrobial-resistant E. Coli from surface waters in southwest Ontario dairy farms


Taggar, G., Rehman, M.A., Yin, X., Lepp, D., Ziebell, K., Handyside, P., Boerlin, P., Diarra, M.S. (2018). Antimicrobial-resistant E. Coli from surface waters in southwest Ontario dairy farms. Journal of Environmental Quality, [online] 47(5), 1068-1078.

Plain language summary

Some dairy farmers rely on surface waters for their operations. However, surface waters require treatment to remove contaminant such as bacteria for milk safety and the dairy cow’s health. On farms, bacteria, such as Escherichia coli, can infiltrate into water sources from animal housing, silage, milk parlor, slurry or manure storage tank through surface runoff or leaching from field drains and ditches. To verify their bacteriological quality including potential presence of antimicrobial resistant bacteria such as Escherichia coli, this study investigates -234 samples from untreated surface water sources for 15 farms located in the south western Ontario. This study confirmed that untreated surface water sources contained numerous type of bacteria including antimicrobial-resistant Escherichia coli which could be circulated in the production environment. The presence of potential harmful bacteria in surface water sources supports the implementation of efficient water treatments before its use in dairy farm operations.


Untreated surface waters can be contaminated with a variety of bacteria, including Escherichia coli, some of which can be pathogenic for both humans and animals. Therefore, such waters need to be treated before their use in dairy operations to mitigate risks to dairy cow health and milk safety. To understand the molecular ecology of E. Coli, this study aimed to assess antimicrobial resistance (AMR) in E. Coli recovered from untreated surface water sources of dairy farms. Untreated surface water samples (n = 240) from 15 dairy farms were collected and processed to isolate E. Coli. A total of 234 E. Coli isolates were obtained and further characterized for their serotypes and antimicrobial susceptibility. Of the 234 isolates, 71.4% were pan-susceptible, 23.5% were resistant to one or two antimicrobial classes, and 5.1% were resistant to three or more antimicrobial classes. Whole genome sequence analysis of 11 selected multidrug-resistant isolates revealed AMR genes including blaCMY-2 and blaCTX-M-1 that confer resistance to the critically important extended-spectrum cephalosporins, as well as a variety of plasmids (mainly of the IncF replicon type) and class 1 integrons. Phylogenetic and comparative genome analysis revealed a genetic relationship between some of the sequenced E. Coli and Shiga toxin-producing E. Coli O157:H7 (STEC), which warrants further investigation. This study shows that untreated surface water sources contain antimicrobial-resistant E. Coli, which may serve as a reservoir of AMR that could be disseminated through horizontal gene transfer. This is another reason why effective water treatment before usage should be routinely done on dairy farm operations. Copyright c

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