Dear Colleagues,

The discovery of antibiotics has revolutionized medicine by enabling the efficient treatment of many life-threatening bacterial infections. The fight against bacteria is turning again into one of the greatest challenges faced by our societies, especially with the spread of multidrug-resistant (MDR) bacteria. In some cases, resistance extends to the entire repertoire of available therapeutic agents (the so-called pan-drug-resistant phenotypes), posing a formidable challenge to antimicrobial therapy. This is an extremely worrying situation that brings us back to the pre-antibiotic era and thus threatens many achievements of modern medicine that rely on antibiotic therapies.

β-lactams are among the most prescribed antibiotics worldwide, mainly due to their weak toxicity and good efficacy. However, their clinical use is currently threatened by the worldwide spread of β-lactamases (BLs) capable of hydrolyzing them, especially among MDR Gram-negative bacteria (GNB). As the incidence of GNB infections for which few effective treatments are available increases, so does the contribution of drug-hydrolyzing enzymes such as β-lactamases to this serious clinical problem. Currently, β-lactamase-mediated resistance does not spare even the newest and most powerful β-lactams (carbapenems), whose activity is challenged by the class B metallo-β-lactamases (MBLs) (e.g., IMP, VIM, NDM) and the classes A and D serine-carbapenemases (e.g., KPC, IMI, GES, OXA-48, OXA-23, OXA-40).

The number of ß-lactamases being described has drastically increased (BLDB reference). They are either point mutant derivatives of well-known enzymes that may lead to modified hydrolysis profiles or to novel enzymes that are rarely described in human samples but may become a future problem. This large heterogeneity of enzymes illustrates the formidable potential of bacteria to adapt themselves to hostile environments and to fight against antibiotics.

This Special Issue is dedicated to all aspects of ß-lactamase research, with a special emphasis on the following topics:

• Their presence in different fields (human, veterinarian and environmental samples);
• Structure–function analysis;
• Epidemiology;
• The genetic basis at the origin of their dispersion (mobile genetic elements and plasmids);
• The origin of ß-lactamase genes;
• Unknown ß-lactamases present in metagenomic samples;
• Novel drugs resistant to beta-lactamase hydrolysis and inhibitors.

Dr. Thierry Naas
Guest Editor

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• ß-lactamases
• multidrug-resistant bacteria
• mobile genetic elements and plasmids
• bacterial resistance
• antibiotic therapies

• ß-Lactamases in Microorganisms (13 articles)
• ß-Lactamases 2.0 in Microorganisms (8 articles)