Are antibiotic-resistant bacteria in soil a threat to WASH?

Around 40% of E. coli bacteria in household soil, with 10% having the potential to cause diarrhoeal diseases, have shown resistance to at least one antibiotic, found an icddr,b study in rural Bangladesh with Swiss collaborators.

Children in rural areas may be exposed to some harmful bugs from soil. Photo: Sumon Yusuf / icddr,b

E. coli is commonly found in the environment, the human and animal intestinal tract is home to some of these as well. While most of these bacteria are harmless and part of good gut health, some are pathogenic or have the ability to cause diseases including intestinal and extra-intestinal infections. Pathogenic E. coli are known to mostly transmit via fecal (since these bacteria live in the intestine) through soil, food or water to oral route from the environment.

Soil overloaded with harmful, especially antibiotic-resistant bacteria can be a real concern because soil encompasses everything and everyone in the environment.

On this World Soil Day, Food and Agriculture Organization of the United Nations (FAO) urges to ‘Be the Solution to Soil Pollution’ to put an end to this invisible pollution degrading our soils and poisoning the food and water we consume.

“Antibiotic resistance in pathogenic E. coli is a public health concern as infections caused by these bacteria are difficult to treat,” says icddr,b Adjunct Scientist Dr Mohammad Aminul Islam, Assistant Professor at Washington State University and one of the senior authors of the study.

People especially children in rural areas are vulnerable to get exposed to these organisms by coming in direct contact with soil, adds Dr Islam, also a member of the WHO Advisory Group on Integrated Surveillance of Antimicrobial Resistance (WHO AGISAR).

The new study with researchers from Swiss Federal Institute of Aquatic Science and Technology (EAWAG), Swiss Tropical and Public Health Institute, and University of Basel, Switzerland was published in Applied and Environmental Microbiology.

Playing with mud is common for children in rural areas. Photo: Rabiul Hasan / icddr,b

It examined whether soil is acting as a reservoir for some of these antibiotic-resistant germs which were found to thrive well in soil, and whether they could affect water, sanitation and hygiene (WASH) interventions since WASH elements are interconnected and inextricably tied to the environment.

Playing with mud is common for children in rural areas, so is skipping handwashing. Evidence quoted in the study suggests that rural children, particularly in the lower- and middle-income countries, often regularly consume soil due to mouthing activity or soil-contaminated hands.

Interestingly, all households studied had domesticated animals including chickens defecating inside the household plots, which increases the odds for these bugs to find an easy way to the playful children.

Moreover, around 13 percent E. coli were resistant to three or more antibiotics and hence classified as multi-drug-resistant (MDR) in the study. Over half of the E. coli isolates from chickens (57%) and humans (54%) were antibiotic-resistant.

A higher concentration of resistant bacteria in human and chicken faeces is potentially contaminating soil with drug-resistant bacteria. But does it also indicate humans and chickens consuming more antibiotics?

“It is crucial to determine the importance of growth and persistence of E. coli and other pathogens in its original context to complement our microcosm evidence. Besides, elucidating the origin and fate of pathogenic bacteria in domestic soil environments is important in order to design effective measures to control transmission.We need to conduct further studies to understand this matter,” responds Dr Islam.

Although we did not find soil to be directly impacting any WASH indicators, our findings do suggest that soil favourably harbours the growth of these bacteria and future studies should consider soil ecology because of soil’s potential to act as a reservoir for antibiotic resistant pathogenic bacteria, the amounts of which were higher than expected, suggests Dr Islam.