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

AbstractThe Joint Monitoring Program relies on household surveys to classify access to improved water sources instead of measuring microbiological quality. The aim of this research was to pilot a novel test for Escherichia coli quantification of household drinking water in the 2011 Demographic and Health Survey (DHS) in Peru. In the Compartment Bag Test (CBT), a 100-mL water sample is supplemented with chromogenic medium to support the growth of E. coli, poured into a bag with compartments, and incubated. A color change indicates E. coli growth, and the concentration of E. coli/100 mL is estimated as a most probable number. Triplicate water samples from 704 households were collected; one sample was analyzed in the field using the CBT, another replicate sample using the CBT was analyzed by reference laboratories, and one sample using membrane filtration (MF) was analyzed by reference laboratories. There were no statistically significant differences in E. coli concentrations between the field and laboratory CBT results, or when compared with MF results. These results suggest that the CBT for E. coli is an effective method to quantify fecal bacteria in household drinking water. The CBT can be incorporated into DHS and other national household surveys as a direct measure of drinking water safety based on microbial quality to better document access to safe drinking water.

The compartment bag test (CBT) for enumerating fecal indicator bacteria: Basis for design and interpretation of results.

For the past several years, the compartment bag test (CBT) has been employed in water quality monitoring and public health protection around the world. To date, however, the statistical basis for the design and recommended procedures for enumerating fecal indicator bacteria (FIB) concentrations from CBT results have not been formally documented. Here, we provide that documentation following protocols for communicating the evolution of similar water quality testing procedures. We begin with an overview of the statistical theory behind the CBT, followed by a description of how that theory was applied to determine an optimal CBT design. We then provide recommendations for interpreting CBT results, including procedures for estimating quantiles of the FIB concentration probability distribution, and the confidence of compliance with recognized water quality guidelines. We synthesize these values in custom user-oriented 'look-up' tables similar to those developed for other FIB water quality testing methods. Modified versions of our tables are currently distributed commercially as part of the CBT testing kit.

Relative benefits of on-plot water supply over other 'improved' sources in rural Vietnam.

OBJECTIVE: Access to improved water sources is rapidly expanding in rural central Vietnam. We examined one NGO-led piped water supply programme to assess the drinking water quality and health impacts of piped water systems where access to 'improved' water sources is already good. METHODS: This longitudinal, prospective cohort study followed 300 households in seven project areas in Da Nang province, Vietnam: 224 households who paid for an on-plot piped water connection and 76 control households from the same areas relying primarily on 'improved' water sources outside the home. The 4-month study was intended to measure the impact of the NGO-led water programmes on households' drinking water quality and health and to evaluate system performance. RESULTS: We found that: (i) households connected to a piped water supply had consistently better drinking water quality than those relying on other sources, including 'improved' sources and (ii) connected households experienced less diarrhoea than households without a piped water connection (adjusted longitudinal prevalence ratio: 0.57 (95% CI 0.39-0.86, P = 0.006) and households using an 'improved' source not piped to the plot: (adjusted longitudinal prevalence ratio: 0.59 (95% CI 0.39-0.91, P = 0.018). CONCLUSIONS: Our results suggest that on-plot water service yields benefits over other sources that are considered 'improved' by the WHO/UNICEF Joint Monitoring Programme.

A summary catalogue of microbial drinking water tests for low and medium resource settings.

Microbial drinking-water quality testing plays an essential role in measures to protect public health. However, such testing remains a significant challenge where resources are limited. With a wide variety of tests available, researchers and practitioners have expressed difficulties in selecting the most appropriate test(s) for a particular budget, application and setting. To assist the selection process we identified the characteristics associated with low and medium resource settings and we specified the basic information that is needed for different forms of water quality monitoring. We then searched for available faecal indicator bacteria tests and collated this information. In total 44 tests have been identified, 18 of which yield a presence/absence result and 26 of which provide enumeration of bacterial concentration. The suitability of each test is assessed for use in the three settings. The cost per test was found to vary from $0.60 to $5.00 for a presence/absence test and from $0.50 to $7.50 for a quantitative format, though it is likely to be only a small component of the overall costs of testing. This article presents the first comprehensive catalogue of the characteristics of available and emerging low-cost tests for faecal indicator bacteria. It will be of value to organizations responsible for monitoring national water quality, water service providers, researchers and policy makers in selecting water quality tests appropriate for a given setting and application.

Evaluation of a quantitative H2S MPN test for fecal microbes analysis of water using biochemical and molecular identification.

The sensitivity and specificity of the H(2)S test to detect fecal bacteria in water has been variable and uncertain in previous studies, partly due to its presence-absence results. Furthermore, in groundwater samples false-positive results have been reported, with H(2)S-positive samples containing no fecal coliforms or Escherichia coli. False-negative results also have been reported in other studies, with H(2)S-negative samples found to contain E. coli. Using biochemical and molecular methods and a novel quantitative test format, this research identified the types and numbers of microbial community members present in natural water samples, including fecal indicators and pathogens as well as other bacteria. Representative water sources tested in this study included cistern rainwater, a protected lake, and wells in agricultural and forest settings. Samples from quantitative H(2)S tests of water were further cultured for fecal bacteria by spread plating onto the selective media for detection and isolation of Aeromonas spp., E. coli, Clostridium spp., H(2)S-producers, and species of Salmonella and Shigella. Isolates were then tested for H(2)S production, and identified to the genus and species level using biochemical methods. Terminal Restriction Fragment Length Polymorphisms (TRFLP) was the molecular method employed to quantitatively characterize microbial community diversity. Overall, it was shown that water samples testing positive for H(2)S bacteria also had bacteria of likely fecal origin and waters containing fecal pathogens also were positive for H(2)S bacteria. Of the microorganisms isolated from natural water, greater than 70 percent were identified using TRFLP analysis to reveal a relatively stable group of organisms whose community composition differed with water source and over time. These results further document the validity of the H(2)S test for detecting and quantifying fecal contamination of water.

Validation of the H2S method to detect bacteria of fecal origin by cultured and molecular methods.

Using biochemical and molecular methods, this research determined whether or not the H(2)S test did correctly identify sewage-contaminated waters by being the first to use culturing and molecular methods to identify the types and numbers of fecal indicator organisms, pathogens, and other microbes present in sewage samples with positive H(2)S test results. For the culture-based method, samples were analyzed for the presence of fecal bacteria by spread plating the sewage sample onto differential and selective media for Aeromonas spp., Escherichia coli, sulfite-reducing clostridia, H(2)S-producing bacteria, and Salmonella/Shigella spp. The isolates were then: (1) tested to determine whether they were H(2)S-producing organisms and (2) identified to the genus and species level using biochemical methods. The molecular method used to characterize the microbial populations of select samples was terminal restriction fragment length polymorphisms. These experiments on sewage provided evidence that positive H(2)S tests consistently contained fecal bacteria and pathogens. There were strong relationships of agreement between the organisms identified by both methods tested. This study is an important advance in microbial water quality detection since it is focused on the evaluation of a novel, low-cost, water microbiology test that has the potential to provide millions of people worldwide access to water quality detection technology. Of prime consideration in evaluating water quality tests is the determination of the test's accuracy and specificity, and this article is a fundamental step in providing that information.