Evaluating the survival and removal of Escherichia coli from surfaces made with traditional and sustainable cement-based materials in field-relevant conditions.

Abstract

Soil household floors are common in low- and middle-income countries (LMICs) and can serve as reservoirs of enteric pathogens. Cement-based floors may interrupt pathogen transmission, but little is known about pathogen survival or removal from cement-based surfaces. This study investigated the survival of Escherichia coli, an indicator of fecal contamination, on cement-based surfaces and evaluated its reduction through common household activities (mopping, sweeping, and walking). We compared E. coli fate on three mixes: (i) ordinary Portland cement (OPC) concrete (used in the United States), (ii) OPC mortar (used in Bangladesh), and (iii) OPC mortar with fly ash (a sustainable alternative to the Bangladesh mix). Additionally, we compared outcomes on cement-based surfaces with and without soil and at two temperatures representing the dry and wet seasons in Bangladesh. After 4 hours on the cement-based surfaces, E. coli decayed more than 1.1 log₁₀(C/C_o) under all conditions tested, which is significantly faster than in bulk soils. The higher temperature increased the decay rate constant (P = 5.56 × 10^-8) while soil presence decreased it (P = 2.80 × 10^-6). Sweeping and mopping resulted in high levels of removal for all mixes, with a mean removal of 71% and 78%, respectively, versus 22% for walking. The concrete and mortar mix designs did not impact E. coli survival or removal (P > 0.20). Cement-based floors made with a fly ash mix performed similarly to traditional cement-based floors, supporting their potential use as a more sustainable intervention to reduce fecal contamination in rural LMIC household settings.

Importance: Cement-based surfaces may serve as a health intervention to reduce the fecal-oral transmission of pathogens in household settings, but there is a critical lack of evidence about the fate of indicator organisms on these surfaces, especially in field-relevant conditions. This study provides some of the first insights into Escherichia coli survival on cement-based surfaces and the effectiveness of daily activities for removing E. coli. Additionally, this study explores the fate of E. coli on cement-based surfaces made with fly ash (which contributes fewer CO₂ emissions) versus traditional cement mixes. We found that E. coli had similar survival and removal efficiencies across all mix designs, demonstrating that fly ash mixes are feasible for use in household settings (e.g., in floors). The findings enhance understanding of fecal-oral transmission pathways and support the use of fly ash mixes in cement-based flooring in future epidemiologic studies assessing effects on enteric disease burdens.