Antibiotics and resistance

Unit responsible:

Monitoring bacteria under surveillance to test their resistance to antibiotics

Our team monitors antibiotic resistance in a large number of bacteria under surveillance. We expose these bacteria to a broad panel of antibiotics in order to test which ones remain effective. The results are then communicated in yearly rapports and scientific publications, and form the basis for therapeutic recommendations by various health authorities. In parallel, we unravel the genetic mechanisms causing this resistance, to enhance our insight into resistance mechanisms among the bacteria circulating in Belgium.

We also participate in (inter)national projects focusing on the antibiotic resistance surveillance, the development of new diagnostic methods and the implementation of advanced technologies in the field.

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Antimicrobial resistance happens when microorganisms (such as bacteria) change after exposure to antimicrobial drugs (such as antibiotics). Microorganisms developing antimicrobial resistance are sometimes called “superbugs”. As a result, the medicines become ineffective and infection persists in the body, increasing the risk of spreading. Antimicrobial resistance increases the cost of healthcare with longer stays in hospitals and more intensive care.

For all pathologies, the health authorities recommend one or two classes of antibiotics for treatment. It is important that we carefully monitor resistance in order to warn them if new resistance mechanisms arise and inform them about the antibiotics which remain effective. In our team, we focus on Salmonella, Shigella, Listeria, Neisseria meningitidis and Mycobacteria isolates. We screen for resistances against a large number of antibiotics listed in the table below, and compare the results to other national and international surveillance studies. We perform all analyses according to ISO 15189 quality standards.

Overview of the tested antibiotics, ranked by organism

*Salmonella/ Shigella*	*Listeria*	*Neisseria meningitidis*	*M. tuberculosis^a*	Nontuberculous Mycobacteria
Ampicillin	Amoxicillin	Amoxicillin	Rifampicin	Amikacin
Azithromycin	Ampicillin	Ampicillin	Isoniazid	Ciprofloxacin
Cefotaxime	Chloramphenicol	Azythromycin	Ethambutol	Clarithromycin
Ceftazidime	Ciprofloxacin	Benzylpenicilline	Moxifloxacin	Ethambutol
Chloramphenicol	Erythromycin	Cefotaxim	Linezolid	Gatifloxacin
Ciprofloxacin	Gentamycin	Chloramphenicol	Amikacin	Linezolid
Colistin	Streptomycin	Ciprofloxacine	Capreomycin	Minocycline
Ertapenem	TMP-SMX	Rifampicine	Ofloxacin	Moxifloxacin
Gentamicin	Amoxicillin		Rifabutin	Rifabutin
Meropenem			Ethionamide	Rifampin
Sulphamethoxazole			PAS	Streptomycin
Tetracycline				TMP-SMX
Tigecycline
Trimethoprim

^a Antibiotics in italic are second-line drugs, and are only tested in case of resistance to rifampicin. TMP-SMX, trimethoprim-sulphamethoxazole; PAS, para-aminosalicylic acid.

A large part of our work is dedicated to the study of the mechanisms which are used by the drug-resistant bacteria to become resistant. This is important for risk assessment, as the resistance mechanisms can sometimes be transferred between bacteria in close contact with each other.

In our lab, we use four main mechanisms for unraveling the genetic cause of resistance:

DNA sequencing, using either classical Sanger analysis of PCR fragments, or Next-Generation Sequencing of entire bacterial genomes.
Targeted multiplex genotyping. We use in-house developed assays which specifically screen for up to 50 possible causes of resistance in a single well using fluorescent beads.
Line probe assays, which are commercial tests that use PCR/reverse hybridisation methods for the rapid detection of mutations associated with drug resistance in M. tuberculosis.
Beacon assays detect M. tuberculosis and associated rifampicin resistance directly from sputum samples using ultra-sensitive PCR. The GeneXpert TB assay is an automated real time based system that has a number of advantages including the fact that it is a closed system.