Surface sampling collection and culture methods for Escherichia coli in household environments with high fecal contamination

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish (US)
Article number947
JournalInternational journal of environmental research and public health
Volume14
Issue number8
DOIs
StatePublished - Aug 22 2017

Keywords

  • Environmental sampling
  • Escherichia coli
  • Fecal contamination
  • Fomites
  • Infections/transmission
  • Methods/microbiology
  • Sanitation
  • Surfaces

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

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