Abstract

The antibacteriai activity of selected aminoglycosides against 487 nosocomial strains of Acinetobacter baumannii isolated from Chilean hospitals between 1990 and 1998 was investigated. Plasmid profiles were determined for some resistant isolates. A high frequency of resistant strains was found for all aminoglycosides assayed, with values ranging from 47% for amikacin (1990-1992) to 88% for gentamicin (1993-1994). The cure of a plasmid greater than 30 kb was associated with the loss of amikacin, kanamycin and neomycin resistance in some isolates. This result suggests that plasmid may harbor the genes encoding for the combination of aminoglycoside-modifying enzymes AAC(6?) /+ APH(3?). Gentamicin resistance was not lost among cured strains, suggesting it may be encoded by genes located on the bacterial chromosome or transposons inserted on the chromosome.