The in-vitro activity of O-demethylfortimicin.

The activity of O-demethylfortimicin against ampicillin, cefazolin and carbenicillin resistant bacteria was determined. O-Demethylfortimicin showed excellent in-vitro activity against Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Ent. agglomerans, Ent. aerogenes, Citrobacter freundii, Proteus vulgaris, Morganella, and Providencia inhibiting these organisms at less than or equal to 3.1 mg/l. It was particularly effective against Ent. cloacae and Serratia marcescens that were resistant to cefotaxime, cefoperazone and moxalactam. O-Demethylfortimicin did not show particularly good activity against Pseudomonas aeruginosa. Acinetobacter or other Pseudomonas species, MIC90 values were 100 mg/l. Combination of O-demethylfortimicin and ticarcillin or cefsulodin tested against Ps. aeruginosa were primarily indifferent. Combination of O-demethylfortimicin and ticarcillin showed partial synergy for 65% of Enterobacter isolates.