source tracking; E. coli; environmental microbiology; gene transfer; fecal indicator bacteria
Verbyla Matthew E., Pitol Ana K., Navab-Daneshmand Tala, Marks Sara J., Julian Timothy R. (2019), Safely Managed Hygiene: A Risk-Based Assessment of Handwashing Water Quality, in Environmental Science & Technology
, 53(5), 2852-2861.
Montealegre Maria Camila, Roy Subarna, Böni Franziska, Hossain Muhammed Iqbal, Navab-Daneshmand Tala, Caduff Lea, Faruque A. S. G., Islam Mohammad Aminul, Julian Timothy R. (2018), Risk Factors for Detection, Survival, and Growth of Antibiotic-Resistant and Pathogenic Escherichia coli in Household Soils in Rural Bangladesh, in Applied and Environmental Microbiology
, 84(24), e01978-18.
Julian Timothy R., Mosler Hans-Joachim, Friedrich Max N. D., Navab-Daneshmand Tala, Montealegre Maria Camila, Gächter Marja, Nhiwatiwa Tamuka, Mlambo Linn S. (2018), Escherichia coli Contamination across Multiple Environmental Compartments (Soil, Hands, Drinking Water, and Handwashing Water) in Urban Harare: Correlations and Risk Factors, in The American Journal of Tropical Medicine and Hygiene
, 98(3), 803-813.
Julian Timothy R (2016), Environmental transmission of diarrheal pathogens in low and middle income countries, in Environmental Science: Processes & Impacts
, 18(8), 944-955.
The goal of this project is to understand the in situ growth kinetics and potential for gene transfer between enteric and environmental strains of E. coli in domestic settings of low income countries. My previous research has demonstrated substantially higher fecal bacteria and pathogen concentrations on the hands, soils, and surfaces in low income countries (i.e., Bangladesh, Peru, Tanzania) than in high income countries (i.e., United States, European Union). Exposure to higher concentrations of fecal bacteria and pathogens is linked to multiple acute and chronic adverse health outcomes, including diarrheal disease, reduced nutrient absorption, reduced vaccine efficacy, stunting, and death. In light of the high levels of contamination of fecal source E. coli in domestic settings, fundamental concerns arise about the nature of the observed E. coli. Concerns include: the extent to which E. coli in these environments are fecal-source versus autochthonous; the ability of the E. coli to persist and thrive in these environments; and the potential for fecal source pathogenic E. coli to induce pathogenicity in autochthonous bacteria through gene transfer.Specifically, I propose to address these emerging concerns through a series of field- and laboratory-based experiments focused on the following questions: -Are there distinctions (genotypic and/or phenotypic) between enteric E. coli strains and the environmental E. coli strains found in the domestic environment (i.e., hands, soils, and surfaces)? -Are E. coli found in domestic environments persistent and/or able to regrow in the environment of domestic settings in tropical climates? If there are distinctions between enteric and environmental E. coli strains, do these disintctions influence persistence and/or regrowth? -Are pathogenic E. coli from enteric sources contributors of pathogenicity islands (e.g., hemolysin production, P-related fimbrie) to autochthonous or naturalized soil microbiota (including environmental E. coli strains) via horizontal gene transfer?The proposed study aims to identify whether or not the detection of E. coli in environmental reservoirs indicates risks for human health from fecal contamination exposures. Increasingly, the presence/absence of E. coli is used as an indicator of the quality of water and sanitation infrastructure in low resource settings. Therefore, the high concentrations of E. coli we have previously detected are currently interpreted to imply high risks to human health in domestic, low-income settings. However, further research in the following areas is needed to improve interpretation of E. coli detection assays: relative prevalence of enteric and environmental E. coli strains, mechanistic differences in enteric and environmental E. coli strains, in situ growth kinetics of E. coli, and potential for horizontal gene transfer between diarrheagenic E. coli and autochthonous bacteria including environmental E. coli strains. The work proposed here will inform fecal contamination exposure remediation efforts and quantitative microbial risk assessment studies intended to improve health and well-being of families exposed to fecal-source E. coli.