title: In vitro activities of novel oxapenems, alone and in combination with ceftazidime, against gram-positive and gram-negative organisms.
abstract: Four novel oxapenem compounds (i.e., AM-112, AM-113, AM-114, and AM-115) were investigated for their beta-lactamase inhibitory activity against a panel of isolated class A, C, and D enzymes, which included expanded-spectrum beta-lactamase enzymes (ESBLs). The oxapenems were potent beta-lactamase inhibitors. Activity varied within the group, with AM-113 and AM-114 proving to be the most active compounds. The 50% inhibitory concentrations for these agents were up to 100,000-fold lower than that of clavulanic acid against class C and D enzymes. As a group, the oxapenems were more potent than clavulanic acid against enzymes from all classes. The ability of these compounds to protect ceftazidime from hydrolysis by beta-lactamase-producing strains was evaluated by MIC tests that combined ceftazidime and each oxapenem in a 1:1 or 2:1 ratio. The oxapenems markedly reduced the MICs for ceftazidime against class C hyperproducing strains and strains producing TEM- and SHV-derived ESBLs. There was little difference between the activity of 1:1 and 2:1 combinations of ceftazidime and oxapenem. The oxapenems failed to enhance the activity of ceftazidime against derepressed AmpC-producing Pseudomonas aeruginosa strains.
authors.affiliation: Life and Health Sciences, Aston University, Birmingham, United Kingdom.
authors.forename: Conor E
authors.initials: CE
authors.lastname: Jamieson
authors.forename: Peter A
authors.initials: PA
authors.lastname: Lambert
authors.forename: Iain N
authors.initials: IN
authors.lastname: Simpson
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins; D002442:Ceftazidime / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D019818:Clavulanic Acid / Q000494:pharmacology; D004357:Drug Synergism; D013293:Enterococcus faecalis / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D006090:Gram-Negative Bacteria / Q000187:drug effects*; D006094:Gram-Positive Bacteria / Q000187:drug effects*; D007769:Lactams; D008826:Microbial Sensitivity Tests; D013211:Staphylococcus aureus / Q000187:drug effects; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000187:drug effects / Q000235:genetics; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: C476288:(1'R,5R,6R)-3-(4-amino-1,1-dimethyl-butyl)-6-(1'-hydroxyethyl)oxapenem-3-carboxylate; C477300:AM 113; C477301:AM 114; C477302:AM 115; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002511:Cephalosporins; D004791:Enzyme Inhibitors; D007769:Lactams; D065093:beta-Lactamase Inhibitors; D047090:beta-Lactams; D019818:Clavulanic Acid; D002442:Ceftazidime; C048795:AmpC beta-lactamases; D001618:beta-Lactamases