Evaluation of an inexpensive growth medium for direct detection of Escherichia coli in temperate and sub-tropical waters
UNICEF, New York, NY, United States; School of Chemistry, University of Bristol, Bristol, United Kingdom; Department of Civil and Environmental Engineering, University of Surrey, Guildford, United Kingdom; Division of Epidemiology, School of Public Health, University of California, Berkeley, CA, United States; CPI International, Santa Rosa, CA, United States; Public Health England, Bristol, United Kingdom; Council for Scientific and Industrial Research, Pretoria, South Africa; Water Institute, University of North Carolina, Chapel Hill, NC, United States; Brightwater Diagnostics Limited, Bath, United Kingdom
The cost and complexity of traditional methods for the detection of faecal indicator bacteria, including E. coli, hinder widespread monitoring of drinking water quality, especially in lowincome countries and outside controlled laboratory settings. In these settings the problem is exacerbated by the lack of inexpensive media for the detection of E. coli in drinking water. We developed a new low-cost growth medium, aquatest (AT), and validated its use for the direct detection of E. coli in temperate and sub-tropical drinking waters using IDEXX Quanti-Tray®. AT was compared with IDEXX Colilert-18® and either EC-MUG or MLSB for detecting low levels of E. coli from water samples from temperate (n = 140; Bristol, UK) and subtropical regions (n = 50, Pretoria/Tshwane, South Africa). Confirmatory testing (n = 418 and 588, respectively) and the comparison of quantitative results were used to assess performance. Sensitivity of AT was higher than Colilert-18® for water samples in the UK [98.0% vs. 86.9%; p<0.0001] and South Africa [99.5% vs. 93.2%; p = 0.0030]. There was no significant difference in specificity, which was high for both media (>95% in both settings). Quantitative results were comparable and within expected limits. AT is reliable and accurate for the detection of E. coli in temperate and subtropical drinking water. The composition of the new medium is reported herein and can be used freely. © Copyright 2015 Bain et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
drinking water; Africa; Article; bacterial growth; bacterial strain; bacterium detection; bacterium isolate; comparative study; controlled study; culture medium; Escherichia coli; limit of detection; measurement accuracy; nonhuman; quantitative analysis; reliability; sensitivity and specificity; tropics; water analysis; water sampling