Bacteria and other pathogens that are resistant to common anti-microbial medications appear to be most abundant in Africa, as well as parts of South-East Asia and other developing regions with a poor record of sewage and sanitation management, according to a new study published in Nature Communications.

The study is based upon close examination of domestic sewage samples from 74 cities in nearly 60 developed and developing countries. It found that high concentrations of pathogens with anti-microbial resistant genes were highly correlated to national sanitation and health indicators.

The far-reaching study by experts from Denmark, the Netherlands, the United Kingdom, Malaysia, Norway, and the World Health Organization, suggests that monitoring sewage concentrations of such pathogens would be a relatively reliable way to track the global prevalence of anti-microbial resistance (AMR), as well as being free of ethical dilemmas associated with studies on human subjects.

The study also suggests that one powerful, neglected strategy for tackling AMR would also be to clean up untreated sewage in developing countries where AMR genes are found to be most prevalent in household sewage waste.

“AMR gene abundance strongly correlates with socio-economic, health and environmental factors, which we use to predict AMR gene abundances in all countries in the world,” states the study, which was led by experts at the National Food Institute of the Technical University of Denmark (DTU Food) as part of a new Global Sewage Surveillance Project (GSSP).

“Our findings suggest that global AMR gene diversity and abundance vary by region, and that improving sanitation and health could potentially limit the global burden of AMR. We propose metagenomic analysis of sewage as an ethically acceptable and economically feasible approach for continuous global surveillance and prediction of AMR.”

Historically, most studies of AMR prevalence have looked primarily at use in human populations, and  strategies to reduce AMR have focused on reducing anti-microbial use in humans, the study notes.

Other factors that scientists have said considered in the transmission of AMR pathogens between people and places include: infection control, sanitation, access to clean water, access to assured quality antimicrobials and diagnostics, travel, and migration. However, the study found little correlation with most of the variables outside of waste/sanitation and health.

“In this study, we found that, irrespective of the diversity of AMR genes, the total AMR abundance was highly correlated with a limited number of World Bank variables, mainly concerning sanitation and health. In contrast, human air travel had no significant influence on AMR abundance,” the study concludes. “Importantly, this suggests that the total AMR abundance is mainly influenced by local/national parameters, and even though all AMR genes might rapidly disseminate and be found in all corners of the world, local selection is required for them to reach appreciable frequencies.

“These findings suggest that improving sanitation, health, and perhaps education as part of the Sustainable Development Goals would be effective strategies for limiting the global burden of AMR.”

According to a 2017 report [pdf] by WHO and UNICEF, some 30 percent of piped sewage worldwide is untreated. Efficiency of traditional waste water plants is also reduced when there are high concentrations of sewage residues.  Most of the world’s sewage, however, is not even piped, but rather contained onsite and only 50 percent of those onsite sewage systems (e.g. septic tanks) are safely managed, the report notes.

This leads to contamination of ground water, surface water and flood waters with both antimicrobial agents that represent the leftovers of medications excreted by humans or just dumped by health facilities, as well as resistant microbes, water and sanitation experts say. Plants can become contaminated via irrigation with sewage water and from the use of sewage sludge as fertilizer. Finally, there can be animal-based contamination from manure and poor manure management.

Despite this, the water and sanitation link to AMR has only recently begun to receive serious policy attention. It was referenced as a pillar of action at a November 2018 “Call to Action” [pdf] meeting of AMR stakeholders in Accra, Ghana, hosted by the Government of Ghana with the Wellcome Trust, as well as the Government of Thailand. The increased attention was due, in part, to findings from a new OECD report Stemming the Superbug Tide, launched just before the meeting.

“This is the first time in such a policy-soaked arena that WSH [water, sanitation and hygiene] was focused upon in terms of a pillar of action against AMR,” said one observer who attended the meeting.

However, the WHO Global Action Plan on Antimicrobial Resistance, adopted by the United Nations General Assembly in 2016 also referred to water and sanitation management in Strategic Objective 3, to “reduce incidence of infection in order to decrease the need for antimicrobial agents in the first place.”

Until now, observers say, the narrative of how to address AMR has been largely focused on biomedical issues, primarily reducing use of antibiotics, and developing new antibiotics. The new research underlines water and sanitation risks as important neglected factors – and wastewater and sanitation treatment as potentially powerful weapons that can be added to the global arsenal of AMR solutions.

Image Credits: Wikimedia Commons.