One Health: AMR transmission with Natacha Couto and Ed Feil
Natacha Couto of the University of Oxford and Ed Feil of the University of Bath join the hosts to examine One Health, with antimicrobial resistance as a central example. They question diagrams that imply unrestricted movement between humans, animals and the environment, and discuss evidence from a large Klebsiella study. The conversation explains why sampling methods, ecological barriers and host context matter when interpreting transmission and disease risk.
Listen to Episode 101: One Health with Natacha Couto and Ed Feil on SoundCloud
In this episode
One Health is broader than AMR
Ed introduces One Health as a framework that developed from One Medicine. For antimicrobial resistance (AMR), it means considering antibiotic use and resistance in healthcare, agriculture and environmental settings such as rivers and soils, rather than treating hospitals as isolated systems.
Natacha emphasises that One Health is not limited to AMR or even to bacterial disease: viruses, fungi and parasites also belong within it. Its wider purpose is to improve health across connected sectors and learn from their different perspectives. Ed agrees, adding that AMR has been described as a quintessential One Health problem because it connects so many of those settings.
What the One Health arrows leave out
The guests call the familiar diagram of people, animals, hospitals and environmental compartments connected by arrows a One Health “confusogram”. They accept that transmission can occur, but argue that arrows alone do not quantify its frequency or consequences. A spillover that infects one host without onward transmission is different from a strain establishing itself in a new population.
Ed argues that attractive figures can carry an unstated hypothesis: that movement is effectively unimpeded. Testing that assumption means investigating ecological barriers, host adaptation and local adaptation. It also means distinguishing movement of bacterial strains from movement of resistance genes and mobile elements, which adds another layer of complexity.
Sampling bias and the SPARK study
Ed explains that adding antibiotics to culture media improves the chance of detecting resistant bacteria, but does not necessarily reveal how common they are in the sampled setting. He contrasts this with SPARK, a study he says had just been accepted by Nature Microbiology.
SPARK sampled hospitals, communities, farms and environmental sites around Pavia in northern Italy over roughly 15 months. The region had a high hospital prevalence of KPC-producing Klebsiella. Without selecting for antibiotic resistance, the researchers sequenced approximately 3,500 genomes and found no carbapenem-non-susceptible Klebsiella pneumoniae outside hospitals, either genotypically or phenotypically.
This did not establish that such bacteria were absent. Ed suggests hospital-adapted clones may be outcompeted outside healthcare, while stressing that findings from northern Italy need not apply to settings with different antibiotic use or human–animal contact.
Resistance genes, expression and fitness costs
A host asks whether maintaining resistance must impose a substantial metabolic burden. Ed replies that experimental evidence varies: some resistance genes or plasmids carry fitness costs, while others show little apparent cost.
In a Bath river study, the guests describe bacteria carrying OXA-48 resistance plasmids without being phenotypically resistant. Selecting for resistance would have missed those plasmids. Natacha also recalls a conference talk on human patients in which plasmid mutations could silence resistance-gene expression, and examples of plasmids expanding alongside particular bacterial clones. Their point is that gene carriage, expression, measured resistance and fitness cannot be treated as interchangeable observations.
Why pathogen and commensal are contextual labels
Natacha uses secondary bacterial infections in dogs with atopic dermatitis to explain how organisms present in healthy hosts can cause disease when the host–microbe balance changes. Ed agrees that context matters, while noting that some organisms are clearly more dangerous than others.
Their examples include Clostridioides difficile overgrowth and E. coli occupying different sites in the body. Disease potential can depend on the microbial community, anatomical location and relatively small genomic changes. Even a proposed virulence factor such as a flagellum is not inherently harmful: Ed points to free-swimming Vibrio splendidus as a counterexample. Virulence therefore cannot be read from a simple list of “bad” organisms or genes.
Where to look, and which questions to ask
The panel separates immediate infection control from understanding where resistance and virulence originate. For day-to-day control, Ed prioritises healthcare settings and community outbreaks, noting that in high-resource settings there is less need to worry about dangerous strains emerging from livestock. Broader questions require studying commensals and non-human systems, including plants, insects and wildlife. Natacha describes the unresolved resource choice between sequencing resistant pathogens and examining susceptible populations before problems expand.
Shared sequencing and analysis tools do not make the epidemiology interchangeable. Tick-borne transmission requires understanding reservoir hosts such as deer, pheasants and shrews; simple hospital contact models are insufficient. Host switches, COVID-19 and habitat changes illustrate further complications. Human-community studies also need social science: behaviour, risk perception, adherence to advice and antibiotic use can all affect transmission.
Highlights
- 00:02:46 — One Health’s relationship to One Medicine and the need to look beyond hospitals
- 00:03:57 — Natacha explains why One Health extends beyond antimicrobial resistance
- 00:05:53 — The One Health confusogram and the need to quantify transmission risk
- 00:09:19 — How attractive figures can conceal assumptions about unrestricted transmission
- 00:15:16 — Resistance-selective sampling and the contrasting design of the SPARK study
- 00:19:12 — Variable fitness costs of resistance genes and plasmids
- 00:22:26 — Canine atopic dermatitis as an example of context-dependent bacterial disease
- 00:27:24 — Choosing between sequencing resistant pathogens and susceptible commensals
- 00:29:40 — Immediate disease control versus understanding the origins of resistance and virulence
- 00:32:35 — Shared analysis tools but different transmission models across hospitals and environmental systems
- 00:34:29 — Natacha contrasts shared tools with different research questions
- 00:35:17 — Social science, risk perception and antibiotic use in human-community studies
In their own words
AMR has been described as a quintessential One Health problem because of this interconnectedness between all the different sort of settings that we have.
— Ed Feil, 00:05:14
I think the tools available are the same but the questions are very different.
— Natacha Couto, 00:34:29
Who is talking
- Lee Katz (host)
- Andrew Page (host)
- Nabil-Fareed Alikhan (host)
- Natacha Couto (guest, University of Oxford)
- Ed Feil (guest, University of Bath)
Questions this episode answers
Is One Health only about antimicrobial resistance?
No. Natacha explains that it also encompasses diseases involving viruses, fungi and parasites, and more broadly seeks to improve health across connected human, animal and environmental sectors.
What is the problem with One Health transmission diagrams?
Arrows show possible connections without measuring how often transmission occurs or whether it leads to onward spread. The guests argue that ecological and biological barriers must be tested rather than assuming unrestricted movement.
What did the SPARK study find outside hospitals?
Across approximately 3,500 sequenced genomes from a regional One Health study around Pavia, the researchers found no carbapenem-non-susceptible Klebsiella pneumoniae outside hospitals. Ed stresses that this does not prove absence, and that the study did not select for antibiotic resistance.
Does finding a resistance gene mean a bacterium is resistant?
Not necessarily. The guests describe resistance plasmids in bacteria that were not phenotypically resistant and discuss how resistance-gene expression can be silenced.
This page was written from a machine transcript of the episode and checked against it. Listen to the episode for the whole conversation.
Show notes
The hosts of the MicroBinfie podcast invite Dr Natacha Couto (University of Oxford) and Professor Ed Feil (University of Bath) as special guests to discuss the concept of “One Health”. One Health is a comprehensive approach that seeks to manage the problem of antimicrobial resistance (AMR) by addressing the use of antibiotics in healthcare, agriculture, and the environment. It aims to improve health outcomes across all sectors to create a better planet. However, the diagrams often used to represent One Health are misleading as they do not take into account the complexity of the transmission of AMR. Therefore, there is a need for a quantitative study to understand and identify the ecological and biological barriers to AMR transmission. Visual aids such as these diagrams are not always accurate and should be approached with caution; scientists should be mindful of the implicit confirmation bias in visually-appealing graphics.
AMR determinants are found in various settings, including animals, the environment, and humans, due to the derived nature of most antibiotics from natural compounds on Earth. Studies have shown that the presence of AMR determinants is not limited to hospitals; they can be found in the environment and surroundings of hospitals. However, they caution that sampling methods can skew results, and it is essential to use a quantitative approach to understand the transmission of AMR across different sectors.
The One Health approach requires understanding the drivers of resistance and virulence and looking beyond human pathogens. Plants, insects, and animals form part of the broader virome and represent systems that are harder to study. There is no clear answer on where to focus resources as both resistant and commensal strains can be important to study. Context is essential when it comes to virulence as the consensual bacteria can become dangerous pathogens in certain situations.
They note that environmental factors play a significant role in disease outbreaks, and understanding the habits of hosts like deer or pheasants, on whom ticks feed on, is crucial. Approaches like outbreak analysis that work in hospitals cannot be used in environmental settings. Disease cannot be studied as if it occurs in a vacuum. Covid-19 has shown how host switches can have severe consequences, but spillover events usually fizzle out before causing any harm. Understanding environmental factors like habitat changes may help tackle disease outbreaks better in the future.
While tools like sequencing and analysis may be equivalent, questions investigated in different settings are vastly different. It is essential to comprehensively understand social science factors such as people’s compliance level and risk perception when studying transmission in human communities. In conclusion, the issue of antimicrobial resistance is complex and requires a multidimensional approach involving different perspectives and fields of study.