Abstract
Empiric quantification of environmental fecal contamination is an important step toward understanding the impact that water, sanitation, and hygiene interventions have on reducing enteric infections. There is a need to standardize the methods used for surface sampling in field studies that examine fecal contamination in low-income settings. The dry cloth method presented in this manuscript improves upon the more commonly used swabbing technique that has been shown in the literature to have a low sampling efficiency. The recovery efficiency of a dry electrostatic cloth sampling method was evaluated using Escherichia coli and then applied to household surfaces in Iquitos, Peru, where there is high fecal contamination and enteric infection. Side-by-side measurements were taken from various floor locations within a household at the same time over a three-month period to compare for consistency of quantification of E. coli bacteria. The dry cloth sampling method in the laboratory setting showed 105% (95% Confidence Interval: 98%, 113%) E. coli recovery efficiency off of the cloths. The field application demonstrated strong agreement of side-by-side results (Pearson correlation coefficient for dirt surfaces was 0.83 (p < 0.0001) and 0.91 (p < 0.0001) for cement surfaces) and moderate agreement for results between entrance and kitchen samples (Pearson (0.53, p < 0.0001) and weighted Kappa statistic (0.54, p < 0.0001)). Our findings suggest that this method can be utilized in households with high bacterial loads using either continuous (quantitative) or categorical (semi-quantitative) data. The standardization of this low-cost, dry electrostatic cloth sampling method can be used to measure differences between households in intervention and non-intervention arms of randomized trials.
Highlights
According to the Joint Monitoring Programme for Water Supply and Sanitation 2017 Update, there is an estimated 4.5 billion people that lack access to safely managed sanitation [1]
We evaluate the effectiveness of a dry electrostatic cloth (SwifferTM; Proctor & Gamble, Cincinnati, OH, USA) sampling method in peri-urban Peruvian household environments with high fecal contamination
The dry cloth recovery method achieved near perfect (105%) sampling efficiency in the laboratory setting compared to the Moore et al [5] study, with an observed average sampling efficiency of 50% for E. coli from directly inoculated swabs pre-moistened with a variety of swab wetting solutions
Summary
According to the Joint Monitoring Programme for Water Supply and Sanitation 2017 Update, there is an estimated 4.5 billion people that lack access to safely managed sanitation [1]. In communities where fecal waste is unsafely managed and enters the environment untreated, high concentrations of pathogens are transmitted through multiple environmental reservoirs [2]. Surfaces are one of these reservoirs that may significantly contribute to the transmission of pathogens. Both human and animal sources of fecal contamination have been found to exist on surfaces (including floors) in the. Res. Public Health 2017, 14, 947; doi:10.3390/ijerph14080947 www.mdpi.com/journal/ijerph
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