Household Microbial Water Quality Testing in a Peruvian Demographic and Health Survey: Evaluation of the Compartment Bag Test for Escherichia coli

Wang, Alice; McMahan, Lanakila; Rutstein, Shea; Stauber, Christine E.; Reyes, Jorge A.; Sobsey, Mark D.

doi:10.4269/ajtmh.15-0717

Cited by 24 publications

(14 citation statements)

References 13 publications

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“…During the January 2016 sampling campaign, the CBT assays were incubated at ambient temperatures, 25–30°C for 40–48 hours (time varied based on incubation temperatures as per the manufacturer’s instructions), whereas the CBT assays performed during the May–July 2016 sampling campaign were incubated at 35°C for 24 hours. 16 , 17 The quantification range of each CBT assay is 1–100 MPN E. coli /100 mL. During the May–July 2016 sampling campaign, one replicate of the raw water was diluted 10× with bottled water and another was diluted 100× to ensure at least one replicate was within the quantification range.…”

Section: Methodsmentioning

confidence: 99%

Performance Evaluation of Gravity-Fed Water Treatment Systems in Rural Honduras: Verifying Robust Reduction of Turbidity and Escherichia coli during Wet and Dry Weather

Brooks

Tenorio-Moncada

Gohil

et al. 2018

The American Journal of Tropical Medicine and Hygiene

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Abstract.This is the first study to document the reduction of turbidity and Escherichia coli throughout the processes of full-scale gravity-fed drinking water plants (GFWTPs) and their downstream distribution systems in rural Honduras. The GFWTPs, which in these cases were designed by AguaClara, use standard treatment processes: coagulation, sedimentation, filtration, and chlorination. During the dry season, we measured E. coli, turbidity, and chlorine residual at five GFWTPs with < 1,000 connections and at three alternative piped-water systems in neighboring communities. Samples were evaluated from the raw water, settled water, filtered water, post-chlorination in the distribution tank, and at a distant-piped household connection. During the dry season, the treated water and household connections serviced by the GFWTPs met World Health Organization (WHO) recommendations for E. coli (< 1 most probable number [MPN]/100 mL). Alternative plants with the same water sources had comparable or higher E. coli and turbidity measurements posttreatment. We examined the performance robustness of two GFWTPs during the transition into the rainy season. The turbidity of the filtered water met WHO recommendations (< 1 nephelometric turbidity units). Escherichia coli was not detected in treated water, indicating that the two GFWTPs can consistently remove particulates and E. coli from source waters containing varying levels of turbidity. During two sampling events during the rainy season, E. coli was detected at the household connection of a GFWTP system with intermittent service and a substandard chlorine residual (geometric mean = 1.0 MPN/100 mL). Strategies to avoid contamination or inactivate E. coli in the distribution system are needed to ensure safe drinking water at the points of delivery, especially for systems with intermittent service.

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Section: Methodsmentioning

confidence: 99%

Performance Evaluation of Gravity-Fed Water Treatment Systems in Rural Honduras: Verifying Robust Reduction of Turbidity and Escherichia coli during Wet and Dry Weather

Brooks

Tenorio-Moncada

Gohil

et al. 2018

The American Journal of Tropical Medicine and Hygiene

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“…In contrast, the more established PC methods produce results in colony forming units (CFU). We had reason to believe that CBT method performance would be comparable to membrane filtration PC methods (Stauber et al, 2014;Wang et al, 2017), but to increase confidence we included the m-ColiBlue24 method to compare against our CBT results. Both methods measure E. coli based on production of β-glucuronidase.…”

Section: Bacteria Samplingmentioning

confidence: 99%

Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater

Nowicki

Lapworth

Ward

et al. 2019

Science of The Total Environment

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Microbial water quality is frequently assessed with a risk indicator approach that relies on Escherichia coli. Relying exclusively on E. coli is limiting, particularly in low-resource settings, and we argue that risk assessments could be improved by a complementary parameter, tryptophan-like fluorescence (TLF). Over two campaigns (June 2016 and March 2017) we sampled 37 water points in rural Kwale County, Kenya for TLF, E. coli and thermotolerant coliforms (total n = 1082). Using three World Health Organization defined classes (very high, high, and low/intermediate), risk indicated by TLF was not significantly different from risk indicated by E. coli (p = 0.85). However, the TLF and E. coli risk classifications did show disagreement, with TLF indicating higher risk for 14% of samples and lower risk for 13% of samples. Comparisons of duplicate/replicate results demonstrated that precision is higher for TLF (average relative percent difference of duplicates = 14%) compared to culture-based methods (average RPD of duplicates ≥ 26%). Additionally, TLF sampling is more practical because it requires less time and resources. Precision and practicality make TLF well-suited to high-frequency sampling in low resource contexts. Interpretation and interference challenges are minimised when TLF is measured in groundwaters, which typically have low dissolved organic carbon, relatively consistent temperature, negligible turbidity and pH between 5 and 8. TLF cannot be used as a proxy for E. coli on an individual sample basis, but it can add value to groundwater risk assessments by improving prioritization of sampling and by increasing understanding of spatiotemporal variability.

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“…Simpler, potentially low-cost alternatives to standard membrane filtration assays are now available for detection of Escherichia coli and other faecal indicator bacteria (FIB). Some are supported by systematic comparative testing [6][7][8][9] . Based on criteria of total cost per test of ≤US$2 per sample and a lower limit of detection of 1 colony-forming unit (cfu) E. coli in 100 ml of drinking-water by culture, we selected two novel assays for evaluation as microbial water safety tests in comparison with EPA Method 1604 (membrane filtration followed by incubation on MI agar) 10 .…”

Section: Introductionmentioning

confidence: 99%

Novel methods for global water safety monitoring: comparative analysis of low-cost, field-ready E. coli assays

2020

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Current microbiological water safety testing methods are not feasible in many settings because of laboratory, cost, and other constraints, particularly in low-income countries where water quality monitoring is most needed to protect public health. We evaluated two promising E. coli methods that may have potential in at-scale global water quality monitoring: a modified membrane filtration test followed by incubation on pre-prepared plates with dehydrated culture medium (CompactDry TM), and 10 and 100 ml presence-absence tests using the open-source Aquatest medium (AT). We compared results to membrane filtration followed by incubation on MI agar as the standard test. We tested 315 samples in triplicate of drinking water in Bangalore, India, where E. coli counts by the standard method ranged from non-detect in 100 ml samples to TNTC (>200). Results suggest high sensitivity and specificity for E. coli detection of candidate tests compared with the standard method: sensitivity and specificity of the 100 ml AT test was 97% and 96% when incubated for 24 h at standard temperature and 97% and 97% when incubated 48 h at ambient temperatures (mean: 27°C). Sensitivity and specificity of the CompactDry TM test was >99 and 97% when incubated for 24 h at standard temperature and >99 and 97% when incubated 48 h at ambient temperatures. Good agreement between these candidate tests compared with the reference method suggests they are suitable for E. coli monitoring to indicate water safety.

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Household Microbial Water Quality Testing in a Peruvian Demographic and Health Survey: Evaluation of the Compartment Bag Test for Escherichia coli

Cited by 24 publications

References 13 publications

Performance Evaluation of Gravity-Fed Water Treatment Systems in Rural Honduras: Verifying Robust Reduction of Turbidity and Escherichia coli during Wet and Dry Weather

Performance Evaluation of Gravity-Fed Water Treatment Systems in Rural Honduras: Verifying Robust Reduction of Turbidity and Escherichia coli during Wet and Dry Weather

Tryptophan-like fluorescence as a measure of microbial contamination risk in groundwater

Novel methods for global water safety monitoring: comparative analysis of low-cost, field-ready E. coli assays

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