Escherichia coli Contamination across Multiple Environmental Compartments (Soil, Hands, Drinking Water, and Handwashing Water) in Urban Harare: Correlations and Risk Factors

Abstract

Abstract.Escherichia coli pathotypes (i.e., enteropathogenic and enterotoxigenic) have been identified among the pathogens most responsible for moderate-to-severe diarrhea in low- and middle-income countries (LMICs). Pathogenic E. coli are transmitted from infected human or animal feces to new susceptible hosts via environmental reservoirs such as hands, water, and soil. Commensal E. coli, which includes nonpathogenic E. coli strains, are widely used as fecal bacteria indicator, with their presence associated with increased likelihood of enteric pathogens and/or diarrheal disease. In this study, we investigated E. coli contamination in environmental reservoirs within households (N = 142) in high-population density communities of Harare, Zimbabwe. We further assessed the interconnectedness of the environmental compartments by investigating associations between, and household-level risk factors for, E. coli contamination. From the data we collected, the source and risk factors for E. coli contamination are not readily apparent. One notable exception is the presence of running tap water on the household plot, which is associated with significantly less E. coli contamination of drinking water, handwashing water, and hands after handwashing. In addition, E. coli levels on hands after washing are significantly associated with handwashing water contamination, hand contamination before washing, and diarrhea incidence. Finally, we observed that animal ownership increases E. coli contamination in soil, and E. coli in soil are correlated with contamination on hands before washing. This study highlights the complexity of E. coli contamination in household environments within LMICs. More, larger, studies are needed to better identify sources and exposure pathways of E. coli—and enteric pathogens generally—to identify effective interventions.

High Genomic Diversity and Heterogenous Origins of Pathogenic and Antibiotic-Resistant Escherichia coli in Household Settings Represent a Challenge to Reducing Transmission in Low-Income Settings

“…First, the pathogenicity potential and acquired antibiotic resistance of environmental strains reaffirm the need for interventions that effectively reduce E. coli across different environmental reservoirs. This represents a major challenge, as multiple previous studies showed no significant impact of sanitation (16), household-level water, sanitation, and hygiene infrastructure (17,28) or an integrated water, sanitation, and hygiene intervention (54) on E. coli concentrations in soils in and around households. Second, the lack of core phylogenetic signal based on source and apparent fluidity of E. coli strains across human, animal, and environmental reservoirs reaffirms the need for integrated interventions that address both human and animal fecal sources (One Health approaches) (55).…”

“…Luo et al reported that the genome sequences of nine strains recovered primarily from environmental sources were phylogenetically distinct from commensal or pathogenic host-associated E. coli (15). In contrast, many settings in low-and middle-income countries (LMICs) are characterized by poor or nonexistent sanitary barriers for both people and animals that lead to fecal-and thus E. coli-contamination of environmental compartments (16)(17)(18).…”

Quantitative assessment of fecal contamination in multiple environmental sample types in urban communities in Dhaka, Bangladesh using SaniPath microbial approach

“…Additionally, while the sample size was appropriate for the primary study objective of conducting an exposure assessment, it may not be sufficient for detecting modest differences between individual neighborhoods or between environmental pathways. Future studies of environmental contamination should increase the sample size for pathways that have large variation and/or cover larger or more diverse geographical regions [72].…”

Drinking Water Safety: Role of Hand Hygiene, Sanitation Facility, and Water System in Semi-Urban Areas of India

“…Second, the lack of robust dataset may be responsible for the relative lack of statistical significance in the dataset. Navab-Daneshmand et al 12 reported the small sample size limitation (97 households) while evaluating E. coli correlations and risk factors in multiple matrices, including soil, hands, drinking water, and handwashing water in a highly densely populated area. By contrast, a strong correlation between visible dirt on hands and FIB levels was previously reported by Pickering et al 14 Those authors evaluated the correlations between visible dirt and observed handwashing behavior using structured observation.…”

“…[8][9][10][11] Hands and water handling practices play an important role in drinking water contamination. [12][13][14] Previously, researchers have investigated the relationships between fecal indicator bacteria (FIB) levels on hands and associated environmental and behavioral factors in source and stored drinking water. 8,15,16 There is strong evidence that high levels of microbial contamination found on the hands of people are related to the poor quality of stored drinking water.…”