Antimicrobial resistance — the new pandemic around the corner? Part 3
-The environmental angle to the AMR challenge
Monitoring animal health and animal-human interactions can help prevent pandemics, as discussed in the second part of this blog series. But the influence of human interactions is not limited to this one dimension. Human interactions with other ecosystems and the environment also form critical components of the one health philosophy.
In the context of AMR, soil, and water are two components of the environment that serve as a storehouse of microbes and offer a medium for their spread.
Soil.
Soil is considered to be the primary reservoir of microorganisms that produce antimicrobials. Antimicrobial production is believed to have evolved 500 million years ago as a mechanism for fungi and bacteria to reduce the population levels of surrounding microorganisms and, therefore, increase the availability of nutrients and other resources in the immediate environment. Plants grown as crops by humans are thus in direct contact with such a rich and dynamic medium enriched with microbes. Intensive agricultural practices with over-reliance on pesticides, fungicides, are reducing the health of soil by disturbing microbial diversity of soil.
Practices considered as ‘traditional’ or ‘organic’, that rely on manure from livestock animals to replenish the nutrients in the soil instead of chemical fertilizers are not as safe as deemed earlier. The widespread use of antibiotics in livestock animals as growth supplements or in prophylactic manner creates a selective pressure for ARGs (antimicrobial resistance genes) in the gut microbiome of the animal, which is then excreted in the faeces. This is a potential source of introduction of ARGs to soil. Manure contains drugs like oxytetracycline, doxycycline and sulphadiazine, whereas sludge contains less water-soluble drugs like ofloxacin, ciprofloxacin, norfloxacin and trimethoprim.
A 2015 study by the Chinese Academy of Sciences identified 156 new antimicrobial-resistant genes in composted manure and sludge. But this still remains an under studied area as the direct link from manure in farms to human health is difficult to establish.
The second feature of intensive farming is use of pesticides to improve yield along with chemical fertilizers. Fungal diseases followed by bacterial diseases are a menace to crops, especially mono-culture type of farms. Naturally, antimicrobials are the second most common type of pesticides after herbicide used on farms. The regulations around introduction of antimicrobials and their use in LMICs are poor.
Thus the use of antimicrobials as pesticides is another way by which microbes in agricultural soil are subjected to selection pressure for ARGs.
Though Bacterial and fungal plant pathogens rarely infect animals and humans, Burkholderia spp. and Pseudomonas aeruginosa, may cause disease in immune-compromised people. Some are opportunistic pathogens like Aspergillus fumigatus while some can harm humans due to their ability to secrete mycotoxins.Thus agricultural soil may act as a source for resistance pathogenic fungus for humans. This problem gets compounded if surface run-offs from agricultural soil reach water bodies.
One of the ways to tackle the spread of AMR to humans via animal manure is to prevent the imprudent use of antimicrobials in livestock production. According to the UN Food and Agriculture Organization (FAO), 62 billion animals are used every year to produce meat, milk, and eggs. This number is expected to double by 2050. More importantly, meat, dairy, and aquaculture industries consume the highest amount of antibiotics worldwide, with their consumption increasing by 70% in the last decade.
Such extensive use of antibiotics in the livestock industry can cause AMR to spread to humans through food.
Another direct way of tackling AMR spread from crops to humans is to develop or use sustainable agricultural practices
by improving the efficiency of inputs for plant growth and food production, and judicious use of fertilizers and pesticides. Advocating for fertilizer stewardship among farmers on similar lines as antimicrobial stewardship among doctors could be useful in this regard.
Water
In addition to soil, water is one of the major environmental drivers of AMR spread. Aquatic environments are considered a naturally active eco-system in terms of horizontal gene transfer due to various microbes existing in the same medium.
Indian aquatic systems are under pressure from the changing rain patterns due to climate change, agricultural run-offs, municipal waste, and industrial effluents. Moreover, major population centers of India are located near water bodies but few enjoy access to clean water for drinking or other purposes.
India is a leading producer of pharmaceuticals in the world, effluents from pharmaceutical units can have high levels of antibiotics in them. Along with this hospital effluents and municipal wastewater can contain antibiotics in varying concentrations, as most of the antimicrobials consumed by humans are excreted through urine or feaces.
Although residues of some classes of antimicrobials degrade rapidly, some such as fluoroquinolones and sulphonamides, are stable. These drugs-types can induce AMR in microbes present in the water bodies, thereby spreading AMR. Presence of antibiotics in such sub-optimal concentrations can drive emergence of antimicrobial-resistant microbes.
For these reasons, wastewater treatment and monitoring are critical to prevent the spread of AMR through improved environmental health. Therefore, stringent antibiotic stewardship to reduce antibiotic load in hospital effluents, regular monitoring of pharmaceutical and hospital effluents, and municipal wastewater is critical to tackle AMR spread. Studies have shown that only 20% — 30% of municipal wastewater and less than 45% of hospital affluents are treated before they are discharged into water bodies.
Policies enforcing stringent wastewater treatment before discharging them, and regular monitoring of the effluents for AMR genes and antimicrobial-resistant microbes are, therefore, critical for one health.
Government and intergovernmental forums should move towards strong enforcement of policies to ensure the judicious use of resources and limited use of antimicrobials, pesticides, and fertilizers in crop and livestock production. They must encourage farmers to adopt sustainable, one-health approaches that take agriculture and environmental health into account in their agricultural practices.
In this direction, FAO, the United Nations Environment Programme (UNEP), WHO, and the World Organisation for Animal Health (WOAH, founded as OIE) launched a new One Health Joint Plan of Action in October 2022. The broad aim of the program is to strengthen collaborations and improve capacity building and coordination across sectors equally to address the health concerns at human-animal-plant-environment interface.
Certain institutions have adopted measures to help farmers solve crop-related problems by improving plant health. For instance, M.S. Swaminathan Research Foundation in Chennai has opened clinics for this purpose. Similar measures from multiple stakeholders could pave the way to better plant and environmental health, which could help curb the spread of AMR, thereby improving human health .
India’s National One Health Mission also involves environmental and plant health components led by stakeholders in the government, such as the Ministry of Environment, Forest and Climate Change, the Department of Animal Husbandry and Dairying, and Indian Council of Agricultural Research. The plan focuses on integrating data for pandemic preparedness and disease control.
The C-CAMP anchored Indian AMR Innovation Hub (IAIH) has identified One Health and Environment as two of the five focus areas. The aim of IAIH is to identify novel solutions for the identified focus areas and help them optimally deploy to bring meaningful impact on the ground.
Disclaimer: The blog is a compilation of information on a given topic that is drawn from credible sources; however, this does not claim to be an exhaustive document on the subject. It is not intended to be prescriptive, nor does it represent the opinion of C-CAMP or its partners. The blog is intended to encourage discussion on an important topic that may be of interest to the larger community and stakeholders in associated domains.
Sources:
https://cabiagbio.biomedcentral.com/articles/10.1186/s43170-022-00118-2
https://blogs.worldbank.org/health/one-health-economics-healthy-people-agriculture-and-environment
https://www.who.int/publications/i/item/sea-whe-15
https://www.psa.gov.in/innerPage/psa-initiatives-covid/one-health-mission/4053
https://www.mssrf.org/small-blog/plant-clinics-to-the-rescue/
https://pubmed.ncbi.nlm.nih.gov/26018772/
https://www.mdpi.com/2077-0472/12/2/289#B24-agriculture-12-00289
