Analysis of two Nocardia brasiliensis class A β-lactamases (BRA-1 and BRS-1) and related resistance to β-lactam antibiotics.

Objective: Molecular determinants of β-lactam resistance are poorly explored for most Nocardia species, such as Nocardia brasiliensis. In this study, we characterised resistance mediated by two β-lactamases in the reference strain N. brasiliensis HUJEG-1 and extended our analysis to nine N.

Modulation of the Specificity of Carbapenems and Diazabicyclooctanes for Selective Activity against Mycobacterium tuberculosis.

Treatment of multidrug-resistant tuberculosis with combinations of carbapenems and β-lactamase inhibitors carries risks for dysbiosis and for the development of resistances in the intestinal microbiota. Using Escherichia coli producing carbapenemase KPC-2 as a model, we show that carbapenems can be modified to obtain drugs that are inactive against E. coli but retain antitubercular activity.

Low-cost anti-mycobacterial drug discovery using engineered E. coli.

Whole-cell screening for Mycobacterium tuberculosis (Mtb) inhibitors is complicated by the pathogen's slow growth and biocontainment requirements. Here we present a synthetic biology framework for assaying Mtb drug targets in engineered E. coli.

On the Hunt for Next-Generation Antimicrobial Agents: An Online Symposium Organized Jointly by the French Society for Medicinal Chemistry (Société de Chimie Thérapeutique) and the French Microbiology Society (Société Française de Microbiologie) on 9-10 December 2021.

The restrictions posed by the COVID-19 pandemic obliged the French Society for Medicinal Chemistry (Société de chimie thérapeutique) and the French Microbiology Society (Société Française de Microbiologie) to organize their joint autumn symposium (entitled "On the hunt for next-generation antimicrobial agents") online on 9-10 December 2021. The meeting attracted more than 200 researchers from France and abroad with interests in drug discovery, antimicrobial resistance, medicinal chemistry, and related disciplines. This review summarizes the 13 invited keynote lectures.

Click and Release Chemistry for Activity-Based Purification of β-Lactam Targets.

β-Lactams, the cornerstone of antibiotherapy, inhibit multiple and partially redundant targets referred to as transpeptidases or penicillin-binding proteins. These enzymes catalyze the essential cross-linking step of the polymerization of cell wall peptidoglycan. The understanding of the mechanisms of action of β-lactams and of resistance to these drugs requires the development of reliable methods to characterize their targets.

Synthesis of Carbapenems Containing Peptidoglycan Mimetics and Inhibition of the Cross-Linking Activity of a Transpeptidase of l,d Specificity.

The carbapenem class of β-lactams has been optimized against Gram-negative bacteria producing extended-spectrum β-lactamases by introducing substituents at position C2. Carbapenems are currently investigated for the treatment of tuberculosis as these drugs are potent covalent inhibitors of l,d-transpeptidases involved in mycobacterial cell wall assembly. The optimization of carbapenems for inactivation of these unusual targets is sought herein by exploiting the nucleophilicity of the C8 hydroxyl group to introduce chemical diversity.

Activity-Based Protein Profiling Reveals That Cephalosporins Selectively Active on Non-replicating Bind Multiple Protein Families and Spare Peptidoglycan Transpeptidases.

As β-lactams are reconsidered for the treatment of tuberculosis (TB), their targets are assumed to be peptidoglycan transpeptidases, as verified by adduct formation and kinetic inhibition of (Mtb) transpeptidases by carbapenems active against replicating Mtb. Here, we investigated the targets of recently described cephalosporins that are selectively active against non-replicating (NR) Mtb. NR-active cephalosporins failed to inhibit recombinant Mtb transpeptidases.

Diazabicyclooctane Functionalization for Inhibition of β-Lactamases from Enterobacteria.

Second-generation β-lactamase inhibitors containing a diazabicyclooctane (DBO) scaffold restore the activity of β-lactams against pathogenic bacteria, including those producing class A, C, and D enzymes that are not susceptible to first-generation inhibitors containing a β-lactam ring. Here, we report optimization of a synthetic route to access triazole-containing DBOs and biological evaluation of a series of 17 compounds for inhibition of five β-lactamases representative of enzymes found in pathogenic Gram-negative bacteria. A strong correlation (Spearman coefficient of 0.

Inhibition Activity of Avibactam against Nocardia farcinica β-Lactamase FAR.

, one of the most frequent pathogenic species responsible for nocardiosis, is characterized by frequent brain involvement and resistance to β-lactams mediated by a class A β-lactamase. Kinetic parameters for hydrolysis of various β-lactams by FAR from strain IFM 10152 were determined by spectrophotometry revealing a high catalytic activity (/ ) for amoxicillin, aztreonam, and nitrocefin. For cephems, / was lower but remained greater than 10 M s A low catalytic activity was observed for meropenem, imipenem, and ceftazidime hydrolysis.

Tryptophan Fluorescence Quenching in β-Lactam-Interacting Proteins Is Modulated by the Structure of Intermediates and Final Products of the Acylation Reaction.

In most bacteria, β-lactam antibiotics inhibit the last cross-linking step of peptidoglycan synthesis by acylation of the active-site Ser of d,d-transpeptidases belonging to the penicillin-binding protein (PBP) family. In mycobacteria, cross-linking is mainly ensured by l,d-transpeptidases (LDTs), which are promising targets for the development of β-lactam-based therapies for multidrug-resistant tuberculosis. For this purpose, fluorescence spectroscopy is used to investigate the efficacy of LDT inactivation by β-lactams but the basis for fluorescence quenching during enzyme acylation remains unknown.

Copper inhibits peptidoglycan LD-transpeptidases suppressing β-lactam resistance due to bypass of penicillin-binding proteins.

The peptidoglycan (PG) layer stabilizes the bacterial cell envelope to maintain the integrity and shape of the cell. Penicillin-binding proteins (PBPs) synthesize essential 4-3 cross-links in PG and are inhibited by β-lactam antibiotics. Some clinical isolates and laboratory strains of and achieve high-level β-lactam resistance by utilizing β-lactam-insensitive LD-transpeptidases (LDTs) to produce exclusively 3-3 cross-links in PG, bypassing the PBPs.

Synthesis of Avibactam Derivatives and Activity on β-Lactamases and Peptidoglycan Biosynthesis Enzymes of Mycobacteria.

There is a renewed interest for β-lactams for treating infections due to Mycobacterium tuberculosis and M. abscessus because their β-lactamases are inhibited by classical (clavulanate) or new generation (avibactam) inhibitors, respectively. Here, access to an azido derivative of the diazabicyclooctane (DBO) scaffold of avibactam for functionalization by the Huisgen-Sharpless cycloaddition reaction is reported.

Peptidoglycan Cross-Linking Activity of l,d-Transpeptidases from Clostridium difficile and Inactivation of These Enzymes by β-Lactams.

In most bacteria, the essential targets of β-lactam antibiotics are the d,d-transpeptidases that catalyze the last step of peptidoglycan polymerization by forming 4→3 cross-links. The peptidoglycan of is unusual since it mainly contains 3→3 cross-links generated by l,d-transpeptidases. To gain insight into the characteristics of peptidoglycan cross-linking enzymes, we purified the three putative l,d-transpeptidase paralogues Ldt, Ldt, and Ldt, which were previously identified by sequence analysis.