Allergies and Antimicrobial Resistance

World Antimicrobial Resistance (AMR) Awareness Week is celebrated each year from the 18th to the 24th of November. This campaign aims to raise awareness and understanding of AMR, with the ultimate goal of improving antimicrobial use to limit the impact of AMR.

Antimicrobial resistance poses a significant threat to global health. It is estimated that 4.95 million deaths were associated with bacterial AMR in 2019 alone. At the United Nations General Assembly High-Level Meeting on AMR held in September this year, world leaders committed to decisive action. The goal set at this meeting was to reduce AMR-related deaths by 10% by 2030.

In regards to human health, one of the actions that has been suggested to reach this target is to ensure that at least 70% of antibiotics used globally belong to the World Health Organization (WHO) Access group of antibiotics.

The WHO has grouped antibiotics into the following three categories based on their clinical importance and potential for the selection of AMR:

1. Access antibiotics have a narrow spectrum of activity, are generally well tolerated and have a lower potential for AMR. These agents should be widely available and are often listed in guidelines for the empiric treatment of common infections;
2. Watch antibiotics typically have a higher risk of selection for AMR, and their use should be carefully monitored to avoid inappropriate use; and
3. Reserve antibiotics are considered last resort antibiotics that should be reserved for treating severe infections caused by multi-drug resistant pathogens.

This is known as the AWaRE (Access Watch Reserve) classification system and can indirectly indicate the appropriateness of antibiotic use. Examples of antibiotics belonging to each group are shown in Table 1.

*Only available via special access scheme (SAS)

Table 1. Examples of antibiotics included in the AWaRE groupings

The WHO publishes the AWaRe Antibiotic Book, which provides guidance on antibiotic choice (including drug, formulation, dose, and duration) in hospital and primary healthcare settings. Importantly, the book also includes guidance on when not to use antibiotics.

Allergy labelling

When looking at the Access group of antibiotics, we can see that beta-lactams feature quite prominently. This is because the penicillins and cephalosporins in that group are among the most effective and safe antibiotics for many infections. However, alternatives to these medications may be needed in the case of allergy.

Penicillin allergy is commonly reported in Australia, with around 10% of the population stating that they are allergic to penicillin. However, studies demonstrate that less than 10% of people reporting a penicillin allergy have a true allergy upon skin testing. There are many possible reasons for this apparent discrepancy. Patients may confuse common adverse effects, such as diarrhoea or nausea, with an allergy. In other cases, a viral rash may be misinterpreted as an allergy if the patient happens to be taking a penicillin at the same time.

Incorrect labelling of penicillin allergy has been identified as a major public health concern. Potential outcomes associated with this include:

• Increased use of alternative antibiotics, which are often broader spectrum;
  • Broader spectrum alternatives are associated with an increased risk of AMR and iatrogenic infections, such as Clostridioides difficile-associated diarrhoea.
  • Alternative antibiotics are typically more expensive.
  • Alternative antibiotics may not be as well tolerated
• Treatment delays; and
• Longer hospital stays.

Accurate documentation of patient allergies is, therefore, crucial. A detailed clinical history should be taken whenever an antibiotic allergy is reported. Patients should be asked about the nature and severity of the reaction, when it occurred, how it was managed, and if other antibiotics have since been tolerated.

In some cases, de-labelling a reported penicillin allergy may be possible after appropriate assessment (i.e. allergy history reconciliation or allergy testing). Studies have found that penicillin allergy de-labelling is associated with reduced AMR, reduced patient morbidity and mortality, and lower treatment costs. Just as importantly, detailed patient assessment also allows for verification of true penicillin allergy.

Allergy testing may be considered for some patients. The Australasian Society of Clinical Immunology and Allergy (ASCIA) recommends that penicillin allergy testing be prioritised for the following patient groups:

• Patients who have frequent infections and require antibiotics several times per year;
• Patients who have infections for which penicillins are the most appropriate antibiotic;
• Patients who are allergic or intolerant to other antibiotics in addition to penicillins;
• Patients with risk factors for infections requiring frequent antibiotic use (e.g. immunodeficiency, significant immunosuppressive therapy, bronchiectasis); and
• Patients with asplenia or who are undergoing splenectomy.

Antimicrobial resistance continues to be a significant health concern. However, there are actions that can be taken to help minimise the impact. Accurate documentation of adverse reactions is just one simple way that healthcare professionals can play their part in reducing AMR, while also directly improving patient outcomes.

To learn more about AMR, head to the WHO campaign page.