One Health: How Environmental Factors Fuel Antimicrobial Resistance

Introduction

Antimicrobial resistance (AMR) is a global health crisis that threatens effective treatment of infections caused by bacteria, viruses, fungi, and parasites. AMR claims approximately 700,000 lives annually.¹ Without urgent intervention, it's projected to cause a loss of 10 million lives and $100 trillion by 2050.¹ A recent CDC report highlights this urgent threat, revealing a staggering 460% increase in drug-resistant bacteria, specifically NDM-producing carbapenem-resistant Enterobacterales, in the U.S. from 2019 to 2023.² Another report by the ECDC showed a 57% increase in bloodstream infections caused by carbapenem-resistant bacteria in the same time period.³

This crisis is not just a medical issue; it’s deeply tied to environmental factors and human behaviour. The overuse and misuse of antimicrobial agents in healthcare, agriculture, and veterinary practices have accelerated the emergence of drug-resistant microbes.¹ This not only complicates treatment options but also poses significant risks to food production and safety, especially in agriculture, where improper antibiotic use in livestock fosters resistance that can transfer to humans through zoonotic diseases.⁴ Furthermore, climate change intensifies the spread of resistant pathogens, as rising temperatures and environmental hazards facilitate the development and transmission of resistance.⁵ This not only complicates infection control efforts but also increases the risk of outbreaks.

To effectively combat AMR, a One Health approach is essential—one that recognises the interconnectedness of human, animal, and environmental health. By integrating these perspectives, we can develop comprehensive solutions that address the complexities of AMR and promote a more sustainable future.

The Interplay Between AMR and the Environment

The spread of antimicrobials and the consequent increases in AMR largely stem from the release of antibiotic residues into the environment.⁶ Key sources include treated and untreated human and animal excreta, as well as residual waste from the pharmaceutical, manufacturing, and healthcare sectors.⁷ These antibiotic residues are considered persistent contaminants; they can remain in the environment for extended periods, ranging from hours to hundreds of days, and in some cases, they may even become permanent fixtures in soil and water systems.⁸

This accumulation of residues enables the environment to act as a reservoir for mobile genetic elements, facilitating their interaction and spread to human and animal hosts.⁹

As these contaminants diffuse through water, soil, and air, they significantly impact ecosystems and public health. Consequently, this creates a complex web of resistance that transcends borders, complicating global efforts to manage AMR effectively.

Agricultural Practices and AMR

Modern agricultural practices, particularly intensive farming and large-scale animal husbandry, significantly contribute to AMR. Antibiotics are frequently administered to promote growth and prevent disease in livestock, leading to residues entering the environment through manure and runoff.¹⁰ This agricultural runoff can contaminate local waters, disrupting microbial communities and fostering the development of resistance. Alarmingly, higher levels of antibiotic-resistant bacteria and resistance genes (ARGs) have been found in farms.^10,11 As this contaminated water is used for irrigation, resistant genes can spread through crops and into the human food chain, creating a challenging cycle of resistance that's hard to break.⁴

Wastewater Management and Pharmaceutical Manufacturing

Improperly treated wastewater can release high levels of antibiotics and resistant bacteria into the environment, creating hotspots for resistance.¹² For instance, hospitals and healthcare facilities generate significant antimicrobial waste, both through patient secretions and discarded medications.¹³ A troubling degree of fluoroquinolone residues has been documented in hospital effluents.¹⁴ Recent studies have also demonstrated the presence of novel ARGs enriched in activated sludge and effluent wastewater, conferring resistance to multiple antibiotics, including aminoglycosides, fluoroquinolones, and β-lactams.¹⁵ Pollution from pharmaceutical manufacturing compounds this issue, with active pharmaceutical ingredients leaking into surface waters and contributing to the increasing rates of ARGs associated with clinically important antibiotics.¹⁶

Climate Change and Biodiversity Loss

Climate change plays a key role in shaping microbial communities and potentially exacerbating AMR. Rising temperatures create favourable conditions for the survival and spread of various pathogens, including bacteria, viruses, and parasites.¹⁷ Additionally, climate-related events like floods can result in the uncontrolled leakage of antimicrobials into the environment, complicating efforts to manage resistance effectively.¹⁸

As ecosystems become disrupted, shifts in microbial populations can occur, potentially introducing new health threats. This is particularly concerning as the loss of biodiversity, driven by environmental degradation and pollution, diminishes the natural microbial diversity crucial for ecosystem health.¹⁹ Healthy soils, rich in diverse microbial life, act as a barrier against AMR. However, when these soils degrade, the spread of resistant strains is accelerated.²⁰ Maintaining healthy soils is essential for preserving the intricate balance of ecosystems, which may play an important role in mitigating the spread of resistance.

Environmental Solutions and Strategies

Tackling AMR requires a multifaceted approach that integrates environmental strategies with robust monitoring and stewardship practices. A crucial step is implementing integrated surveillance systems to track AMR levels across ecosystems—soil, water, and wildlife. This data could inform targeted interventions and policy decisions, promoting responsible antimicrobial use.

A key aspect of effective monitoring is antimicrobial susceptibility testing, which offers insights into how sensitive bacteria are to specific antibiotics. Coupled with advances in technology, such as genomic sequencing and biosensors, we can enhance our ability to monitor AMR in real time. These tools allow us to track resistant genes, deepening our understanding of how AMR spreads.

Environmental stewardship also plays a critical role in combating AMR. Efforts to reduce pollution, conserve biodiversity, and adopt sustainable agricultural practices can limit the spread of resistant microorganisms. For instance, policies aimed at minimising the use of medically important antimicrobials in agriculture, particularly as growth promoters in livestock, have shown promise. Countries like Denmark and Sweden have successfully enacted bans on these drugs, demonstrating effective policy responses.²¹

Sustainable agricultural practices are equally essential. Techniques such as crop rotation, organic farming, and integrated pest management promote soil health and biodiversity, reducing the need for chemical inputs.²² These practices lower the risk of developing resistant strains while contributing to long-term environmental sustainability.

Ultimately, addressing AMR is not just about controlling resistant infections; it’s about nurturing the ecosystems that sustain our health and well-being.

Conclusion

The fight against AMR is a pressing global health crisis that goes beyond medicine; it’s deeply interconnected with our environment and everyday behaviours. To effectively tackle AMR, we must embrace a One Health approach that recognises the links between human, animal, and environmental health. By fostering responsible practices, promoting biodiversity, and implementing robust monitoring systems, we can create a healthier world for ourselves and future generations.

This conversation is at the heart of our Going Macro on Macro podcast. In our first series, we explored the relationships between animal and human health in the context of AMR. We’re excited to announce that our upcoming Series 2 will focus on the environment, AMR, and surveillance. Be sure to listen on your favourite streaming platform and stay tuned for the release—we can’t wait to explore these critical issues with you and learn how we can work together to create a sustainable future.