Antimicrobial resistance: what is it and why does it matter?

22/01/2024

In the last article of our One Health series, we discussed a short list of zoonotic diseases and their routes of transmission. But what happens when a human or animal develops an infection or associated disease? If there is a treatment available it will likely be administered, but these treatments aren’t always effective. An increasingly common term in both the medical and non-medical communities is “antibiotic resistance”. The more encompassing term, however, is “antimicrobial resistance”. So what is the difference between them? Antibiotics specifically target bacteria, while antimicrobials target various microbes, or microorganisms. This includes bacteria but also viruses, parasites, fungal spores, amongst others. This is an important distinction because we are not only in a period of increasing antibiotic resistance, but overall “antimicrobial” resistance.

What is meant by “resistance”?

At its core, it means microorganisms that could previously be killed or stopped from replicating are surviving treatment. There are several ways a microorganism can achieve survival, including changing itself so it is no longer targeted by the treatment, preventing or limiting medication uptake, and developing ways to degrade the medication so it is not present in sufficient amounts to be effective.

What contributes to the increase in resistance?

Several actions we take as humans contribute to the development of resistance, including blanket use of antimicrobials, patients failing to complete a treatment course, prescribing an inappropriate medication or dose for the patient, and health professionals prescribing or patients asking for antimicrobials in an inappropriate situation. We may believe that antibiotics are a magic fix for sickness—but this is not always the case. An antibiotic will not be effective against viruses, as it is meant to treat bacteria. The same can be said for using antibiotics for an uncomplicated parasitic infection. In such a case, an antiparasitic medication used alone is more appropriate. These situations increase exposure to antimicrobials, which in turn provides more opportunities for microorganisms to adapt and cease being susceptible to the drug.

The same factors contribute to antimicrobial resistance in veterinary medicine. Blanket use of antimicrobials administered to food producing animals, which is luckily decreasing in practice, gives plenty of opportunity for resistance to arise. Additionally, companion animal owners often fail to complete courses of antimicrobial prescriptions once their pet appears to be healthy. Both situations contribute to resistance.

To complete the One Health circle, residues from these treatments can be found in the environment. Once the medication is processed by the body, some components may exit via bodily fluids or materials. This can potentially increase the exposure of both humans and animals to residues of antimicrobial agents. Additionally, if a human or animal with resistant microorganisms excretes the actual organisms into the environment, it allows others to be exposed to resistant infection.

Why does this matter?

The short answer is that the medical world is running out of effective antimicrobials. Treatments that were once successful for common infections are no longer effective, as microorganisms adapt very quickly. Medical professionals reserve a few antibiotics for rare cases to ensure they remain effective, and there is plenty of research on preventing resistance to medications such as anthelmintics (to treat worm infections). Luckily, antimicrobial use, particularly antibiotic use, has decreased across both human and animal medicine. But the responsibility lies with all of us. Health professionals must prescribe responsibly, and patients must finish courses of medication even if feeling better, not pushing for antibiotics every time they feel unwell.

The next article in the series will cover some important tips to avoid zoonotic diseases, so keep an eye on this space.

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