In Vitro Activity of Tobramycin and Gentamicin

Abstract

The in vitro antimicrobial activity of tobramycin and gentamicin was compared against 362 (3,5,6,10,13,14,18 RESULTSIn vitro susceptibility of various microorganisms to tobramycin and gentamicin. The relative susceptibility of various microorganisms to tobramycin is shown in Fig. 1. S. aureus was the most susceptible of all of the bacteria tested; the MIC for all strains was less than 0.075 ,ug/ml. The Escherichia coli, Pseudomonas, and Klebsiella-Enterobacter strains, and the indole-positive strains of Proteus except P. rettgeri, had comparable susceptibility: the MIC for 85 to 95%, of all of these organisms

Susceptibility of Pseudomonas aeruginosa to Tobramycin or Gentamicin Alone and Combined with Carbenicillin

“…Tobramycin was the most biologically active of the three. This antibiotic has been reported to be more active on a per weight basis against P. aeruginosa than gentamicin by other workers (1,5,7,15), whose results compare favorably with ours. This is an especially important finding, as the serum levels of gentamicin and tobramycin are similar after comparable doses (18).…”

“…Tobramycin, an aminoglycoside antibiotic, has been found to be highly active against P. aeruginosa (1,5,15,16). On a weight basis it is frequently two to four times more active than gentamicin against clinical isolates of P. aeruginosa.…”

Studies on the Susceptibility of 150 Consecutive Clinical Isolates of Pseudomonas aeruginosa to Tobramycin, Gentamicin, Colistin, Carbenicillin, and Five Other Antimicrobials

“…It can be noted that more than half (53%) of the 150 isolates had an MIC of 0.5 ug or less of tobramycin per ml, whereas 1.5 Mg of gentamicin per ml was required to inhibit 50% of the susceptible isolates. Only three isolates had an MIC of 4 Mg of tobramycin per ml, with all others being 2 gg or less per ml.…”

“…Only a small percentage of the isolates were inhibited by the other drugs used. By using a minimal inhibitory concentration of 4 ,ug/ml in brain heart infusion broth as the level of susceptibility, it was found that only three of the isolates showed resistance to tobramycin, whereas 20 of the isolates were resistant to gentamicin. Approximately half of the isolates were inhibited by 0.5 Mg/ml or less of tobramycin, whereas 1.5 Mg of gentamicin per ml was required to inhibit 50% of susceptible strains.…”

In Vitro Activity of Gentamicin, Amikacin, and Netilmicin Alone and in Combination with Carbenicillin Against Serratia marcescens

“…Newer aminoglycoside antibiotics, such as tobramycin and amikacin, have exhibited greater in vitro activity than gentamicin against some strains ofPseudomonas and other gram-negative bacilli (4,5,11,15,17,25,45). Amikacin, in particular, has been shown to be effective against S. marcescens both in vitro (4,25,35,44) and in clinical infections (10,19,36).…”