In vitro antimicrobials activity against endemic Acinetobacter baumannii multiresistant clones.
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.
Rodriguez
Carlos Hernan
CH
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
De Ambrosio
Alejandra
A
Bajuk
Milena
M
Spinozzi
Mariela
M
Nastro
Marcela
M
Bombicino
Karina
K
Radice
Marcela
M
Gutkind
Gabriel
G
Vay
Carlos
C
Famiglietti
Angela
A
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
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