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Drivers of AMR

What are the main drivers of antimicrobial resistance? In this article, factors encouraging AMR spread are explored.
So first of all diagnosing UTI this is clearly an old image, but actually looking at the urine and it is a very good test if urine is crystal clear or gin clear how we want to describe it, then that has got a very high negative predictive value and it is unlikely that the patient has a urinary tract infection. Most people will be aware of the to dip or not to dip project and that was presented at the BSAC spring meeting two years ago by Liz Beach. I mention it again, because the findings were so remarkable.
And if we remember what this project was about, was improving the use of urine dipsticks in care homes in the South of England, where they had noticed in an audit two years before that something like 2/3 of patients had received an antibiotic in the previous year. And that over half of those antibiotics were because of urinary tract infection in inverted commas, and most of those infections have been diagnosed by the use of a urine dipstick. So what they did was use community pharmacists to educate care staff on appropriate use of dipsticks and particularly the emphasis on not using a dipstick if a patient was completely asymptomatic and obviously that the concepts behind asymptomatic bacteriuria.
And as a result of that, they showed a phenomenal reduction in antibiotic prescribing as we can see here, between a half and 2/3 of antibiotics reduced. And I’m not going to go into the detail of that particularly. But what I wanted to emphasise was that what I thought was really important was that, they also looked for potential adverse consequences of the intervention that they performed. And I think that as a general theme we will see that if you do take restrictive action to reduce inappropriate antibiotic– sorry diagnostic testing in general and if you look for adverse consequences you do not find them.
And I think part of the challenge going forward, will be to actually demonstrate the patient benefit from doing this as well. So they look for unplanned admissions UTI and urosepsis didn’t find it. And they also demonstrated that they were reduced calls to GPs for the management of UTIs as well. So there were positive outcomes all around so this intervention, very simple intervention. A similar sort of thing is being done elsewhere this was a study that was performed in two veterans hospitals in the southern part of the US.
And the dotted line is the main intervention hospital sorry, the control hospital and the solid line is the intervention hospital and we can see it the data published as a comparative interrupted time series. And what they did was to try to reduce the sampling of urine from patients with urinary catheters. And they were able to demonstrate that the number of samples went down, of course it’s the whole point of their intervention. And but also that patients had significantly reduced treatment for asymptomatic bacteriuria. And again, in terms of looking for potential adverse outcomes they also demonstrated that it’s not shown on the chart that, there was no change in the treatment of UTIs which is defined as patients with symptoms.
So again, there was no obvious adverse outcome from that intervention. This is a very similar study done on two ICUs. And here the laboratory only sampled, or cultured rather the urine if there was high urea.
Again, this is a sort of interrupted time series with the pre-intervention on the left hand side of the charts and the intervention on the right. And they were able to show firstly at the top that the number of cultures performed was less, they demonstrated they were able to identify fewer patients with bacteriuria. Again, both of those completely understandable. But this is the whole point of the study that was their intervention. But interestingly, if we look at the bottom, antibiotic days of therapy did not really change.
And what they found in the ICU setting was that, apparently patients were not being prescribed antibiotics for urine infections but the clinicians clearly thought they had an infection of something else and they just described the antibiotics anyway. In some respects, I think this is still a positive outcome because it showed they weren’t being mislabeled as having infections from a urinary source.

The video above is from a presentation Nick Brown gave at the BSAC Spring conference 2021, outlining some of the findings of the “To Dip or Not To Dip” project. This is an example of a driver of resistance and the talk outlines how this project helps reduce prescribing.

In step 3.2 we learned that antimicrobial resistance mechanisms can occur naturally as part of the natural defences of microorganisms, especially with most antimicrobial agents being naturally produced. Here, we look at some factors which encourage the spread of resistance, driving a global increase in antimicrobial resistance.

Though resistance is a natural phenomenon, evidence exists for the role of human, animal and agricultural antimicrobial uses as the main drivers of AMR.

Antimicrobial use, misuse and overuse

Use of antimicrobial agents in human medicine exerts selective pressure through increased exposure to the agents prescribed; depending on the agents used, microorganisms with the right AMR mechanisms are thus selected for as they can survive antimicrobial courses and reproduce.

Increased antibiotic usage has led to more populations at risk and growing antibiotic resistance and superbugs

If you require a text version of the above image, this is available as a PDF

Rapid uptake in anti-infective usage is driven by both patient volume and resistance

Such use may not always be appropriate, with broad-spectrum agents often started empirically for cases of suspected infections that may not be supported by the final diagnosis following further laboratory investigations.

Additionally, antimicrobial use, misuse and overuse is also seen in veterinary and agricultural settings, with various studies in scientific literature attributing AMR, in part, to these areas (outside of use in human medicine).

Inadequate infection prevention and control (IPC)

Inadequate IPC strategies are key in spreading resistant microorganisms, especially in healthcare settings where the rise of healthcare-associated infections (HAIs) exemplifies the consequences associated with poor IPC practices. This WHO infographic summarises the role of IPC in preventing antibiotic resistance in healthcare, and can be applied for other antimicrobials.

General IPC guidelines advocate:

  • Wearing appropriate personal protective equipment (PPE)

  • Hand hygiene at the appropriate moments, including between patients and other tasks, after using the bathroom, before eating or touching (staff or patient) food, and after sneezing or coughing

  • Regular cleaning of surfaces

  • Never re-using needles or syringes

In areas of the world where access to clean water is limited, and other areas of sanitation are also inadequate, adhering to the above guidelines is more challenging and microorganisms (resistant or not) have more opportunities to spread between patients and to the environment.

Addressing such issues of antimicrobial use and infection prevention and control present important areas in slowing antimicrobial resistance, and will be further explored in Week 4.

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Introduction to Practical Microbiology

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