In vitro and in vivo antibacterial activities of dactimicin, a novel pseudodisaccharide aminoglycoside, compared with those of other aminoglycoside antibiotics.

When compared with astromicin, amikacin, gentamicin, and sisomicin, dactimicin was similar to astromicin in in vitro activity and was more active than amikacin and gentamicin against the clinical isolates of Serratia marcescens, but less active against Pseudomonas aeruginosa. Dactimicin and astromicin were active against many gentamicin- and amikacin-resistant bacteria expressing aminoglycoside-modifying enzymes, with the exception of aminoglycoside 3-acetyltransferase. However, dactimicin was more resistant than astromicin to inactivation by aminoglycoside 3-acetyltransferase, probably owing to the protective action of the formimidoyl group. The in vivo activity of dactimicin, assessed by the 50% effective doses against systemic infections in mice, was similar or superior to that of astromicin and was superior or inferior to that of amikacin depending on the strains tested.