2.1 Processes involved in the development and transmission of AMR

Within and between the different One Health domains (humans, animals and the environment), a number of processes can occur that are involved in the development and transmission of AMR.

  • Emergence: AMR can emerge within any domain. This process can occur through evolution (that is, mutations in the DNA) or through transfer of ARGs on mobile genetic elements (plasmids) that can spread to other bacterial species. These ARGs include ‘indigenous’ ARGs, which are already present in the environment without human influence.
  • Introduction: AMR can be transferred from one domain to another, meaning that one domain can act as a ‘source’ of AMR being introduced to another domain.
  • Transmission/exposure: Humans can be exposed to AMR through contact with any other domain.

If you are unsure about the concepts of ‘mutation’ and ‘gene transfer’, and how they relate to AMR development and transmission, you may like to study the course Introducing antimicrobial resistance before continuing.

Activity 2 gives you an opportunity to think about the processes involved in the development and transmission of AMR in your setting.

Activity 2: AMR processes in your setting

Timing: Allow 5 minutes

Before you touch upon these processes in more detail, think about your local setting. Can you think of one example of each of the following?

  • How resistant bacteria or ARGs can be introduced into the environment from another domain.
  • How humans can be exposed to resistant bacteria or ARGs through contact with the environmental domain.

Discussion

There are many possible answers to this activity. Here are a couple of examples:

  • Resistant bacteria and ARGs can develop in the gut of farm animals and be excreted in manure. When this manure is used as fertiliser or when it runs off into nearby soil and water systems, it introduces resistant bacteria and ARGs into the environmental domain.
  • Humans can be exposed to resistant bacteria or ARGs by swimming in or coming into contact with natural water bodies such as lakes or rivers.

The processes or pathways of introducing AMR into the environment and of exposure of humans to the environment that you identified in Activity 2 are examples of the many ways in which AMR in the environmental domain is linked with the other domains. In the following sections of this course you will explore this multitude of interactions between and within domains. You will use information from Introducing a One Health approach to AMR to identify more ways that AMR (resistant bacteria and ARGs) can be introduced from other domains into the environment. If you have not studied this course you should complete it first and then continue studying AMR in the environment (this course).

In Activity 3 you will start to study the emergence, introduction and transmission processes in more detail.

Activity 3: AMR transmission routes

Timing: Allow 20 minutes

Look at Figure 4, which shows the three One Health domains. One possible transmission pathway, via drinking water to farm animals, is highlighted by an arrow. Thinking about your local environment, suggest three more transmission routes that link the environmental compartment and the other domains shown in Figure 4. Consider transmission both to and from humans and animals. If you can, print a PDF copy of Figure 4 so that you can draw in your own arrows.

Described image
Figure 4 The three linked One Health domains. One possible transmission pathway between the environmental domain (drinking water) and the animal domain is highlighted.
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Three circles showing AMR emergence in animals, humans and the environment. Examples of AMR emergence in the environment include agricultural fields/products, drinking water (which has a transmission route linked to animals), water for recreation, water for household use, floods and waterways. Examples of AMR emergence in animals include manure, run-off from farms and slaughterhouse/wet markets waste. Examples of AMR emergence in humans include sewage, hospitals and antibiotic production facilities.

Figure 4 The three linked One Health domains. One possible transmission pathway between the environmental domain (drinking water) and the...

Discussion

There are many possible pathways that could be found in Figure 4; some will be more important than others in your particular setting. Almost any suggestion is correct! Some examples the course authors thought of are as follows:

  • AMR can be introduced from humans and animals to the environment through:
    • human wastewater or wastewater from animal industries entering waterways
    • human or animal waste being used for fertilising agricultural fields.
  • AMR can be transmitted from the environment to humans through:
    • drinking water
    • recreation in water
    • contact with water for household purposes or during floods
    • contaminated food, e.g. vegetables.
  • AMR can be transmitted from the environment to animals through:
    • drinking water
    • contaminated feed, e.g. vegetables.

Now let’s look more specifically at the impact on and of humans in the environment.

2 One Health and the environment

3 Humans and the environment: exposure and exacerbation