Human faeces-associated extended-spectrum β-lactamase-producing Escherichia coli discharge into sanitation systems in 2015 and 2030: a global and regional analysis
Authors: David Berendes, Amy Kirby, Joe Brown, Astrid L Wester
Journal: The Lancet Planetary Health (2020)

<h2>Summary</h2><h3>Background</h3> Improving management of and treatment within sanitation waste streams could slow the development and transmission of antimicrobial-resistant organisms, but the magnitude of impact has not been quantified. Extended-spectrum β-lactamase (ESBL)-producing <i>Escherichia coli</i> are a major cause of antimicrobial-resistant infections and are frequently detected in faecal waste streams, making them model indicators of the distribution of antimicrobial-resistant organisms that are transmitted through the faecal–oral route. We aimed to estimate the mass of faeces containing ESBL-producing <i>E coli</i> entering different levels of the sanitation ladder globally and by WHO region to determine the global scale at which sanitation infrastructure serves as a vehicle for dissemination of antimicrobial-resistant organisms. <h3>Methods</h3> In this global and regional analysis, we used publicly available sanitation coverage data from the WHO/UNICEF Joint Monitoring Programme and most recent available scientific literature on human faecal production (2018) and carriage of ESBL-producing <i>E coli</i> by healthy individuals (2016) to estimate the quantity of faeces that has been discharged that contains ESBL-producing <i>E coli</i> for 2015 and projected for 2030. We estimated the mass of faeces containing ESBL-producing <i>E coli</i> by WHO region and at different levels of the Sustainable Development Goal sanitation ladder—ie, into at-least basic (ie, safely managed or basic) systems, limited systems, and unimproved systems, and via open defecation. We modelled three scenarios in which the proportion of ESBL-producing <i>E coli</i> among all <i>E coli</i> that was excreted by carriers varied on the basis of the scientific literature: 100% (scenario A), 10% (scenario B), or 1% (scenario C). <h3>Findings</h3> Under scenario B, we estimated that approximately 19 billion kg of faeces carrying ESBL-producing <i>E coli</i> was excreted in 2015 globally. Approximately 65·8% (1·2–120 billion kg depending on modelled scenario) of this faecal biomass was managed in at-least basic sanitation systems, 8·4% (160 million–16 billion kg) in limited sanitation systems, 14·4% (270 million–27 billion kg) in unimproved sanitation systems, and 11·4% (220 million–22 billion kg) was openly defecated. The regions with the highest proportion of openly defecated faeces containing ESBL-producing <i>E coli</i> were the South-East Asia (29·4%) and African (21·8%) regions. The South-East Asia, Western Pacific, and African regions produced 524 billion kg (63%) of the total global human faecal biomass, but 16·9 billion kg (90%) of faeces containing ESBL-producing <i>E coli</i> under scenario B. By 2030, estimates under scenario B will have approximately doubled to 37·6 billion kg of faeces carrying ESBL-producing <i>E coli</i> under the most conservative projections. <h3>Interpretation</h3> At-least basic sanitation does not guarantee effective removal or inactivation of antimicrobial-resistant organisms from faecal biomass. However, our findings indicate the need for mitigating transport of antimicrobial-resistant organisms via sanitation systems that are not safely managed, including open defecation, which might result in direct environmental discharge and subsequent risk of transmission back to humans. <h3>Funding</h3> None.