In-vitro activity of carbenicillin and results of treatment of infections due to pseudomonas with carbenicillin singly and in combination with gentamicin

The clinical effectiveness of carbenicillin and the combination of carbenicillin and gentamicin was evaluated in 33 patients with infections due to Pseudomonas. In all 17 patients with infections of the urinary tract, at least temporary steriliza­tion of the urine occurred, and 9 of 12 patients from whom adequate followup cultures were made could be classified as bacteriologic and clin­ical cures. Carbenicillin was not as effective in the treatment of infections at other sites since a bacteriologic cure was achieved in only 1 of the 5 patients treated for such infections. Combina­tion therapy with carbenicillin and gentamicin was associated with a favorable clinical response in 10 patients who had serious Pseudomonas in­fections, and a bacteriologic and clinical cure was achieved in 5 of them. Combination therapy did not prevent the appearance of Pseudomonas with increased resistance to carbenicillin; however, the frequent synergistic effects of these 2 anti­biotics was such that organisms resistant to car­benicillin were still inhibited by levels of the combined antimicrobials that were clinically achievable.