title: In vitro evaluation of antibiotic synergy for NDM-1-producing Enterobacteriaceae.
abstract: OBJECTIVE
  To analyse the in vitro activity of colistin, fosfomycin and tigecycline alone or in combination against enterobacterial NDM-1 producers.
  
  
  METHODS
  MIC values of colistin, fosfomycin and tigecycline were determined for 28 NDM-1-producing enterobacterial isolates. In vitro synergy combination testing was performed for eight clinical isolates and one Escherichia coli transconjugant (six being susceptible to the three antibiotics) using microdilution and chequerboard techniques.
  
  
  RESULTS
  MICs of colistin, fosfomycin and tigecycline were determined, showing that one-third of NDM-1-producing isolates were resistant or intermediate to at least one of the three drugs. Nevertheless, in vitro synergistic activity was observed for colistin plus fosfomycin and colistin plus tigecycline in very rare cases.
  
  
  CONCLUSIONS
  Synergistic activity was observed for colistin and fosfomycin, and colistin and tigecycline in rare cases, most of the interactions being indifferent.
authors.affiliation: Service de Bactériologie-Virologie, INSERM U914 'Emerging Resistance to Antibiotics', Hôpital de Bicêtre, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine et Université Paris-Sud, K.-Bicêtre, Paris, France. beatrice.bercot@lrb.aphp.fr
authors.forename: Béatrice
authors.initials: B
authors.lastname: Berçot
authors.forename: Laurent
authors.initials: L
authors.lastname: Poirel
authors.forename: Laurent
authors.initials: L
authors.lastname: Dortet
authors.forename: Patrice
authors.initials: P
authors.lastname: Nordmann
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D003091:Colistin / Q000494:pharmacology; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D005578:Fosfomycin / Q000494:pharmacology; D006801:Humans; D008826:Microbial Sensitivity Tests; D008911:Minocycline / Q000031:analogs & derivatives / Q000494:pharmacology; D000078304:Tigecycline; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D005578:Fosfomycin; D000078304:Tigecycline; D001618:beta-Lactamases; C552864:beta-lactamase NDM-1; C063912:carbapenemase; D008911:Minocycline; D003091:Colistin