title: In vitro antimicrobials activity against endemic Acinetobacter baumannii multiresistant clones.
abstract: BACKGROUND
  Multidrug-resistant strains of Acinetobacter baumannii have been reported increasingly around the world. The administration of an association of antibiotics has been proposed to create an active combination and to prevent the emergence of resistance.
  
  
  METHODS
  The activity of colistin, rifampicin, gentamicin, imipenem and their associations was evaluated by means of killing curves in fourteen isolates belonging to three endemic PFGE types, in a university hospital of Buenos Aires city. The 14 isolates were selected on the basis of different mechanisms responsible for resistance to carbapenems and different susceptibility to colistin.
  
  
  RESULTS
  The mechanism responsible for the resistance to imipenem was the production of OXA-23 and OXA-58 carbapenemases. Heteroresistance to colistin was observed in six isolates. The associations colistin-rifampicin and colistin-imipenem were synergistic in heteroresistant isolates and prevented the development of colistin-resistant mutants. The association imipenem-gentamicin was bactericidal in gentamicin susceptible isolates, whereas the association imipenem-rifampicin was always indifferent.
  
  
  CONCLUSIONS
  The antimicrobial activity and the presence of synergy are related to the antimicrobials' susceptibilities irrespective of the PFGE type or the OXA-carbapenemase produced.
authors.affiliation: Laboratorio de Bacteriología, Departamento de Bioquímica Clínica, Hospital de Clínicas José de San Martín, Facultad de Farmacia y Bioquímica. Universidad de Buenos Aires. Buenos Aires, Argentina. carlos_hernanrodriguez@hotmail.com
authors.forename: Carlos Hernan
authors.initials: CH
authors.lastname: Rodriguez
authors.forename: Alejandra
authors.initials: A
authors.lastname: De Ambrosio
authors.forename: Milena
authors.initials: M
authors.lastname: Bajuk
authors.forename: Mariela
authors.initials: M
authors.lastname: Spinozzi
authors.forename: Marcela
authors.initials: M
authors.lastname: Nastro
authors.forename: Karina
authors.initials: K
authors.lastname: Bombicino
authors.forename: Marcela
authors.initials: M
authors.lastname: Radice
authors.forename: Gabriel
authors.initials: G
authors.lastname: Gutkind
authors.forename: Carlos
authors.initials: C
authors.lastname: Vay
authors.forename: Angela
authors.initials: A
authors.lastname: Famiglietti
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology / Q000378:metabolism / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D001118:Argentina; D003091:Colistin / Q000008:administration & dosage*; D024901:Drug Resistance, Multiple, Bacterial; D004357:Drug Synergism; D004359:Drug Therapy, Combination; D019353:Endemic Diseases; D005839:Gentamicins / Q000008:administration & dosage*; D006801:Humans; D015378:Imipenem / Q000008:administration & dosage*; D008826:Microbial Sensitivity Tests; D012293:Rifampin / Q000008:administration & dosage*; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D015378:Imipenem; C466679:beta-lactamase OXA-23; D001618:beta-Lactamases; C534889:beta-lactamase OXA-58, Acinetobacter baumannii; D012293:Rifampin; D003091:Colistin