Can diagnostic tests help to identify Antimicrobial Resistance (AMR)?

Yes, of course they can! In this short blog we will learn what diagnostic tests are, and their valuable role in the management of infections, especially of those ones caused by Antimicrobial Resistant germs.

Let’s start from the basics. Diagnostic tests can detect the presence or absence of an infection, or alternatively point out evidence of a previous infection. They are very helpful tools not only to demonstrate the broad type of infection, (i.e., whether it is viral, bacterial, fungal, or caused by a parasite) but also to identify the type of microbial species responsible. Finally diagnostic tests can define an infection’s susceptibility (and resistance) to various antimicrobials medicines.

Diagnostic tests are based upon different investigations and technologies and, to simplify, we may divide them into two main groups:

• The first group of diagnostic methods includes tests designed to detect the type of microorganism causing an infection. Microbiologists can use a microscope to directly visualise microorganisms (microscopy) or try to study the growth of the microorganism over time using what is called media on a petri dish (culture) which is then heated in an incubator. This helps them to detect nucleic acids (DNA or RNA) or proteins belonging to microbes (respectively molecular assays, and antigen detection assays).
• The second group comprises tests able to measure human biomarkers. For example, some tests can identify biomarkers of infection, such as C reactive protein (CRP) produced by the human body in response to an infection, while other ones can detect antibodies, molecules made by the white blood cell to fight dangerous microbes.

So, what is the role of diagnostic tests in managing antimicrobial resistant infections?

Diagnostic tests can support clinicians to make an accurate diagnosis. Indeed, when managing patients with an infection, physicians need to identify the cause of the illness, to decide whether to prescribe an antimicrobial medicine like an antibiotic and, in this case, select the most appropriate one for a successful outcome.

On the contrary, prescribing an antimicrobial medicine without the help of diagnostics may increase the chance of an ineffective treatment. For example, an antibiotic which only treats bacterial infections can be prescribed unnecessarily for a viral infection.

On the other hand, an infection caused by a bacteria resistant to a certain class of antibiotics, might mistakenly be prescribed the wrong antibiotic instead of one that might be effective. Prescribing the wrong antimicrobial medicine for an infection that won’t respond to it can promote the emergence and further development of AMR

Therefore, the identification of microorganisms, and antimicrobial susceptibility or resistance may change the management of an infection, by enabling an early targeted therapy with proven activity against the microbe responsible for the disease. A correct diagnosis is paramount to using antimicrobial medicines appropriately.

Some traditional laboratory infection investigations have long turnaround times. For example, cultures require time for the microorganisms to grow, and therefore may take hours to days to provide a definitive result. However, today physicians can use rapid tests capable of returning reliable results within minutes to hours. They are especially useful during a patient visit to a health service, or in clinical situations requiring quick decisions, as in life-threatening infections. Point-of-care tests are performed near or at the site of a patient and can help clinicians in making a quick and correct diagnosis and defining an appropriate antimicrobial therapy.

Moreover, diagnostics play a crucial role in identifying asymptomatic individuals who are carriers of antibiotic-resistant bacteria in health care facilities. Screening tests enable infection prevention and control measures to be rapidly implemented, which is essential to prevent the spread of antimicrobial resistant infections among patients, and the development of outbreaks.

Finally, diagnostics support surveillance systems, because resistant microbes’ emergence and spread can be identified as early as possible and monitored in real time.

Although the emergence of resistant microorganisms is a natural phenomenon, both the overuse and inappropriate use of antimicrobials represent as the primary drivers of resistance.

Diagnostic tests can support physicians’ decisions, in this way contributing to reduce the unnecessary or ineffective use of antimicrobials, and preserving the effectiveness of these precious, but vulnerable, medicines for generations to come. As patients, it is equally beneficial to understand the role of diagnostics for AMR.