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Abstract E. coli and total coliforms are the most widely used indicator organisms for microbial monitoring of drinking water and recreational freshwater. In many remote and low-resource settings, however, conventional laboratory methods for quantifying these indicators are challenging or infeasible to perform due to limited access to laboratory facilities. The availability of rapid, low-cost methods for quantifying indicator organisms in freshwater samples without the need for laboratory facilities is crucial to facilitate the rapid and robust monitoring of microbial water quality in these types of settings. The global misuse and abuse of antimicrobials have contributed to the rise of antimicrobial resistance. Thus, simple culture methods are needed to detect indicators of such bacteria in freshwaters. In 2021, the World Health Organization released the Tricycle protocol to address this issue by providing guidance for culture- based detection of extended-spectrum beta-lactamase (ESBL)-producing E. coli in environmental samples. Our research goal was to compare the 100-ml sample volume ESBL E. coli quantal and enumerative commercial tests against the more complex Tricycle protocol to detect and quantify ESBL E. coli in surface waters. Both commercial tests gave results comparable with the results obtained using the Tricycle protocol, and the quantal and enumerative commercial tests were easier and faster to perform than the Tricycle protocol. Keywords: E. coli , antibiotic resistance, extended-spectrum beta-lactamase, ESBL, field test methods, surface water Comparison of the Extended-Spectrum Beta-Lactamase (ESBL) E. coli Compartment Bag Test Method to the World Health Organization Tricycle Protocol in North Carolina Surface Waters
Cindy Fan Department of Public Health, College of Pharmacy & Health Sciences, Campbell University Emily S. Bailey, PhD Department of Public Health, College of Pharmacy & Health Sciences, Campbell University
table, low-cost, semiquantitative procedure for quantifying E. coli in drinking water and surface water samples using ambient tem- perature incubation (Gronewold et al., 2017; Stauber et al., 2014; Wang et al., 2017). A newer version of this simple culture test for E. coli in a plastic bag uses a gel medium to detect and quantify E. coli and total coliforms as colonies. Once mixed with a water sample, the gel medium hardens in a short time and E. coli colonies then develop and are counted after an overnight incubation. The increasing global misuse and abuse of antimicrobials in clinical, veterinary, and agricultural settings have contributed to the rise of antimicrobial resistance, which is a stated One Health global concern (World Health Organization [WHO], 2016). This rise created an urgent need to develop and use harmonized culture methods to detect and quantify an E. coli indicator of antimi- crobial resistance for all settings. In 2021, the World Health Organization (WHO, 2021) released the Tricycle protocol to address this issue by providing guidance on the culture- based detection of extended-spectrum beta- lactamase (ESBL) E. coli in environmental, clinical, and animal agriculture samples. To better address the need to detect and quantify ESBL E. coli in environmental waters, new versions of these simple commercial tests included the same beta-lactam antibiotic that is used in the Tricycle protocol. The goal of our research was to compare the two commercial tests—the 100-mL sam- ple volume ESBL E. coli MPN (most prob- able number) CBT test and the GEL ESBL CFU test—to gauge the results against the WHO Tricycle protocol. To our knowledge, this study is the first to compare these meth- ods using field samples of environmental surface waters.
Introduction E. coli and total coliforms are the most widely used indicator organisms for microbial moni- toring of drinking water and recreational freshwater. In many remote and low-resource settings, however, conventional laboratory methods for quantifying these bacterial indi- cators are challenging or infeasible to per- form due to the absence of timely access to laboratory facilities within allowed holding times and temperatures (Organisation for
Economic Co-operation and Development, 2019; Sargeant et al., 2019). The availabil- ity of rapid, low-cost commercial methods for quantifying these indicator organisms in freshwater samples without the need for laboratory facilities provides rapid and con- venient monitoring of microbial water quality in such settings. The compartment bag test (CBT) is one such method that has been validated in the field in a variety of settings as a simple, por-
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Volume 87 • Number 4
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