title: In-vitro study of the synergy between beta-lactam antibiotics and glycopeptides against enterococci.
abstract: The synergy between glycopeptides and beta-lactams was studied using different techniques such as broth macrodilution, killing curves and agar dilution combined with agar diffusion. Two glycopeptide-resistant enterococci isolated from different clinical samples were used. Results showed different effects with significant changes in MICs. Antibacterial activity was related to the concentration of glycopeptide and beta-lactam for Enterococcus faecalis 8253, while for Enterococcus faecium 8072 a paradoxical effect was observed. With this strain, the best synergic effect was detected at teicoplanin concentrations of 1-4 mg/L, but antibacterial activity was reduced at concentrations of 8, 16 and 32 mg/L. No synergic effect was observed with vancomycin. The combination of agar dilution with agar diffusion techniques may constitute a simple method for routine detection of synergic effects between glycopeptides and beta-lactams.
authors.affiliation: Institute of Microbiology, University of Brescia, Spedali Civili, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Ravizzola
authors.forename: E
authors.initials: E
authors.lastname: Cabibbo
authors.forename: L
authors.initials: L
authors.lastname: Peroni
authors.forename: M
authors.initials: M
authors.lastname: Longo
authors.forename: P C
authors.initials: PC
authors.lastname: Pollara
authors.forename: M
authors.initials: M
authors.lastname: Corulli
authors.forename: R
authors.initials: R
authors.lastname: Pizzi
authors.forename: F
authors.initials: F
authors.lastname: Dima
authors.forename: C
authors.initials: C
authors.lastname: Fallacara
authors.forename: A
authors.initials: A
authors.lastname: Turano
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D016983:Enterococcus / Q000187:drug effects*; D013293:Enterococcus faecalis / Q000187:drug effects; D016984:Enterococcus faecium / Q000187:drug effects; D006020:Glycopeptides / Q000494:pharmacology*; D015378:Imipenem / Q000494:pharmacology; D008826:Microbial Sensitivity Tests / Q000379:methods; D010878:Piperacillin / Q000494:pharmacology; D017334:Teicoplanin / Q000494:pharmacology; D014640:Vancomycin / Q000494:pharmacology; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D006020:Glycopeptides; D047090:beta-Lactams; D017334:Teicoplanin; D014640:Vancomycin; D015378:Imipenem; D010878:Piperacillin