This STREP aims at the elucidation of the molecular mechanisms of resistance to inhibitors of cell wall synthesis in bacteria responsible for severe nosocomial and community-acquired infections. It is focused on ß-lactams, the major class of antibiotics in current clinical use, and on resistance due to modification of the cell wall synthesizing machinery and to production of ß- lactamases, the most prevalent mechanisms in Gram-positive and Gram-negative bacteria, respectively. The specific aims concerning S. pneumoniae, S. aureus, and Enterococcus are (i) to elucidate the 3D structures and structure/activity relationships of the transpeptidase domains of the penicillin- binding proteins (PBPs), and (ii) to understand the role of non-PBP factors critical for resistance, including the glycosyltransferases, that cooperate with the transpeptidases for peptidoglycan polymerisation, the tRNA-dependent ligases, that synthesize the precursor side chain specifically required for the transpeptidase activity of low-affinity PBPs, and recently discovered regulatory factors. These studies will form a reference to globally assess the modifications of the structure, function, and dynamics of the peptidoglycan assembly pathways responsible for emergence of resistance. Concerning Pseudomonas, Acinetobacter, and the Enterobacteriaceae, the specific aims are (i) to identify new ß-lactamases and determine their 3D structures, (ii) to elucidate the regulation of ß- lactamase gene expression and the mechanisms responsible for their mobility, and (iii) to establish the relative contribution of ß-lactamases, membrane impermeability, and drug efflux to resistance. The knowledge of all aspects of resistance gained during the STREP will be essential to understand the consequences of antibiotic use on the dissemination and modification of resistance genes, and, more immediately, to develop novel diagnostic tools, based on the identification of speci#
Keywords:
Antibiotic resistance; -lactams; regulation of expression; gene mobility; targets; crystallography
|
