Effect of triethylenetetramine dihydrochloride on the antibiotic susceptibility of Pseudomonas aeruginosa.

A chelating agent, triethylenetetramine dihydrochloride, interacted synergistically in vitro with both gentamicin and carbenicillin against a clinical isolate of Pseudomonas aeruginosa designated Ps 15. The minimal inhibitory concentrations of carbenicillin and gentamicin for Ps 15 in a 50% serum-Trypticase soy broth were 250 and 72.9 mug/ml, respectively. However, addition of triethylenetetramine dihydrochloride to the 50% serum-Trypticase soy broth reduced the minimal inhibitory concentration of both antibiotics approximately 10-fold. A comparison of the growth of Ps 15 in 50% serum-Trypticase soy broth containing either of the antibiotics showed that a rapid decrease in the percentage of survivors only occurred when the chelating agent was present.