Evaluating Human Sensory Perceptions and the Compartment Bag Test Assays as Proxies for the Presence and Concentration of Escherichia coli in Drinking Water in Western Kenya

The Sustainable Development Goal (SDG) 6.1 aims to ensure that “safely managed drinking water services” are free of fecal pollution.1 Evaluating the presence of fecal pollution is difficult in low-resource settings partially due to lack of financial, logistical, and technical resources. In such settings, organoleptic properties (smell, taste, and appearance) are relied upon to infer the quality of drinking water. There are no published studies that have evaluated the associations of organoleptic properties and the microbial quality of drinking water. In this study, we evaluated the associations of perceived quality and organoleptic properties (taste and smell) of stored drinking water (SDW) with the presence of Escherichia coli in 35 households in western Kenya. The compartment bag test (CBT; Aquagenx, LLC, Chapel Hill, NC) is a novel method that shows promise to quantify E. coli in potable water in low-resource settings.2 Its attributes include incubation at ambient temperatures (25–40
C), no specialized equipment required, and an adequate quantification range (1–100 MPN/100 mL).3,4 Comparisons of E. coli concentrations measured using CBT and membrane filtration (USEPA Method 1604) in environmental waters around Atlanta, GA, were correlated.5 In three regions in Peru, concentrations of E. coli in SDW measured by CBT in the field and membrane filtration in a laboratory were similar.6 Herein, we compared the concentrations of E. coli quantified by CBT and Colilert (IDEXX Laboratories, Inc., Westbrook, ME) in source water and SDW from 35 households in western Kenya. Data were collected in the Nyanza Region, Kenya, within an observational pregnancy cohort ( identifier: NCT).7 We used STATA 14 (StataCorp LP, College Station, TX) to randomly select five households to visit in each of the seven clinic catchment areas from a pool of participating households. All participants were 9–12 months postpartum. If participants elected not to participate or were not available, another household was randomly selected. In January–February 2016, we collected samples of SDW at the participating households and surveyed participants on the organoleptic properties (taste and smell) and perceived overall quality of their SDW using a Likert ladder scale used in the parent cohort study (1 = “poor” to 5 = “excellent”; Supplemental Figure 1). We accompanied participants to source waters to collect samples, and photographed the supply for classification. The study protocol was reviewed and approved by the Kenyan Medical Research Institute Scientific and Ethics Review and Cornell University Institutional Review Board ([; ], May 8, 2015). Informed consent of the participants was obtained. Six 100-mL replicates of SDW from each household and six 100-mL replicates of corresponding source water were collected using Whirl-Pak® Thio Bags® (Nasco, Fort Atkinson, WI). Source water was not collected if the household’s primary drinking water was rainwater or bottled water. There was no SDW in four households, but corresponding source water was collected. Samples were stored in a cooler at ambient temperature (£ 21
C) for £ 6 hours because ice was not readily available. After transport, water samples were stored at 4
C for £ 24 hours. For each water sample, three 100-mL replicates each were analyzed using Colilert Quanti-Tray® /2000 (IDEXX Laboratories) and the CBT. We followed the manufacturers’ instructions and samples were incubated at 35
C for 24 hours. Bottled water was used for negative controls and analyzed alongside samples. The range of quantification of the mean concentrations of E. coli enumerated with Colilert and CBT were 0.3–2,419.6 and 0.3–100 MPN/100 mL, respectively. Samples that were negative for the presence of E. coli were recorded as 1 MPN/ 100 mL, and were evaluated at 0.15 MPN/100 mL (half the quantification limit of the mean of three replicates that individually had a detection limit of 1 MPN) in subsequent analyses. Results above the upper limit of quantification of Colilert and CBT were reported as 2,419.6 and 100 MPN/100 mL, respectively, and were evaluated at the upper limits of the methods in subsequent analyses (2,420 and 100 MPN/ 100 mL, respectively). Statistical analyses were evaluated using IBM SPSS Statistics for Windows, Version 22.0 (IBM, Corp., Armonk, NY), * Address correspondence to Yolanda M. Brooks, Cornell University, 433 Campus Avenue, Hollister Hall Room 468, Ithaca, NY 14850. E-mail: 1005 and significance was considered at α = 0.05. Logistic regression analyses evaluated the presence of E. coli (mean concentrations ³ 1 MPN/100 mL) in SDW as measured by CBT or Colilert to the perceptions of taste, smell, and the overall quality of SDW at “5 = excellent quality” (reference group) compared with all other ratings “ 5 = below excellent” to normalize the categorical data. Wilcoxon matched-pairs signed rank test evaluated differences between the mean concentrations of E. coli using Colilert and CBT of source water and SDW from each household. A linear regression evaluated the relationship between the log transformed mean concentrations of E. coli me