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Antimicrobial Resistance

Diagnostic tests to prevent antibiotic resistance and treat resistant bacteria


Jean Carlet

World Alliance Against Antibiotic Resistance (WAAAR), President

Antibiotic resistance is a very important challenge for physicians, in particular in the therapy of multi-resistant micro-organisms. It is also key to differentiate viral from bacterial infections.

Physicians need to change their treatment strategy

There is an important overuse of antibiotics worldwide particularly in people living outside of health facilities, which represents 80% of antibiotic consumption. This overuse is due in most part to the use of antibiotics to “treat’ viral infections.

A first key issue is to try to avoid empirical treatments. For that, physicians have to make the diagnosis of infection, try to know if the infection is viral or bacterial, and sometimes have access very quickly to the type of bacteria, and its resistance profile. Too often, they decide to treat the patients empirically, because it is far more easy than to try to have a precise diagnostic. This results in a prolonged therapy for unnecessary antibiotics and increase the antibiotic pressure.

Diagnostic tests must be available and respected by GPs

For people living outside the health facilities, it has been shown that 40 to 50% of antibiotics are useless. Several diagnostic tests are already available but are not often used by general practitioners (GPs). For example, the rapid-strepto test is easy to use, and freely available in France, but it is used by only 20% of GPs. The point of care usage of C Reactive Protein (CRP) or procalcitonin (PCT) is also very easy to use nowadays. The rapid strepto-test can even be done in the pharmacies. GPs are not at all ready to let pharmacy people perform this test. Biologists are not at all ready to let GPs perform CRP and PCT. In most countries physicians are not keen to share information and therapy with other health care workers.

In the emergency units, the problematic is almost similar, although the access to biology is very easy. CRP or PCT is rarely used.

In the hospitals, in particular for the most severe patients, it is key to have rapidly access to the type of bacteria, and its profile of resistance. For that, the first important rule is to sample the infection site if accessible (urine, lung…), or to perform at least 2 blood cultures, of course before to start antibiotics. Many physicians, including intensivists, do not respect this simple rule, although it is emphasised in all recommendations. It is of paramount importance to follow this rule in patients with sepsis.

Progress is being made every day in diagnosing infection

Of course, the rapid access to the type of bacteria and its resistance profile is also key and requires further research. Many progresses have been made in this respect in the last few years. New culture milieu allowed a considerable shortening of the results, in particular for the blood cultures. Maldi-tof technique gives the name of the bacteria in a few minutes, but for now, do not provide the resistance profile of the bacteria. It will be available shortly. PCR are widely used. It would be of paramount importance to detect bacteria directly in the blood, and not just after culture.

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