["In vitro" activity of gentamicin, sisomicin and tobramycin against "pseudomonas aeruginosa" strains from hospital sources (author's transl)].

The in vitro activity of two amynoglicosidic antibiotics, tobramycin and sisomicin, against 215 strains of Pseudomonas aeruginosa isolated from clinical specimens during the years 1972-1975, was evaluated in comparison with that of gentamicin. Tobramycin showed a greater activity than sisomicin and gentamicin. At the concentration of 5 mu/ml tobramycin resulted inhibitory on 94% of strains and sisomicin and gentamicin on 78.6% and 49.8% of strains respectively. The susceptibility of Pseudomonas aeruginosa strains to gentamicin decreased from 1972 to 1975, with an increasing of resistant strains of 23%. In an evaluation of possible cross-resistance of 14 strains of Pseudomonas aeruginosa highly resistant (MIC greater than or equal to 25 gamma/ml) to gentamicin, 13 showed a high degree of resistance also to sisomicin; on the other hand 7 strains highly resistant to gentamicin was sensitive to tobramycin at concentration less than or equal to 10 gamma/ml.