title: Distinctive Binding of Avibactam to Penicillin-Binding Proteins of Gram-Negative and Gram-Positive Bacteria.
abstract: Avibactam is a novel non-β-lactam β-lactamase inhibitor that covalently acylates a variety of β-lactamases, causing inhibition. Although avibactam presents limited antibacterial activity, its acylation ability toward bacterial penicillin-binding proteins (PBPs) was investigated. Staphylococcus aureus was of particular interest due to the reported β-lactamase activity of PBP4. The binding of avibactam to PBPs was measured by adding increasing concentrations to membrane preparations of a variety of Gram-positive and Gram-negative bacteria prior to addition of the fluorescent reagent Bocillin FL. Relative binding (measured here as the 50% inhibitory concentration [IC50]) to PBPs was estimated by quantification of fluorescence after gel electrophoresis. Avibactam was found to selectively bind to some PBPs. In Escherichia coli, Pseudomonas aeruginosa, Haemophilus influenzae, and S. aureus, avibactam primarily bound to PBP2, with IC50s of 0.92, 1.1, 3.0, and 51 μg/ml, respectively, whereas binding to PBP3 was observed in Streptococcus pneumoniae (IC50, 8.1 μg/ml). Interestingly, avibactam was able to significantly enhance labeling of S. aureus PBP4 by Bocillin FL. In PBP competition assays with S. aureus, where avibactam was used at a fixed concentration in combination with varied amounts of ceftazidime, the apparent IC50 of ceftazidime was found to be very similar to that determined for ceftazidime when used alone. In conclusion, avibactam is able to covalently bind to some bacterial PBPs. Identification of those PBP targets may allow the development of new diazabicyclooctane derivatives with improved affinity for PBPs or new combination therapies that act on multiple PBP targets.
authors.affiliation: Centre d'Étude et de Valorisation de la Diversité Microbienne (CEVDM), Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Abdelhamid
authors.initials: A
authors.lastname: Asli
authors.affiliation: Centre d'Étude et de Valorisation de la Diversité Microbienne (CEVDM), Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Brouillette
authors.affiliation: Cerexa, Inc., Oakland, California, USA.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Krause
authors.affiliation: AstraZeneca Pharmaceuticals, Waltham, Massachusetts, USA.
authors.forename: Wright W
authors.initials: WW
authors.lastname: Nichols
authors.affiliation: Centre d'Étude et de Valorisation de la Diversité Microbienne (CEVDM), Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, QC, Canada francois.malouin@usherbrooke.ca.
authors.forename: François
authors.initials: F
authors.lastname: Malouin
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D053961:Azabicyclo Compounds / Q000378:metabolism / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D004359:Drug Therapy, Combination; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D046915:Penicillin-Binding Proteins / Q000378:metabolism*; D011485:Protein Binding; D065093:beta-Lactamase Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D053961:Azabicyclo Compounds; D046915:Penicillin-Binding Proteins; D065093:beta-Lactamase Inhibitors; C543519:avibactam; D002442:Ceftazidime; D001618:beta-Lactamases