Aztreonam compared with gentamicin for treatment of serious urinary tract infections

52 patients with serious urinary tract infections were randomised to receive either aztreonam (35) or gentamicin (17). In the aztreonam group 23 patients had unqualified cures, 6 cures with relapse, and 6 cures with reinfection; the comparable numbers in the gentamicin group were 9, 1, and 4. There were no failures with aztreonam and 3 with gentamicin. The most important determinant of outcome was the presence or absence of urological abnormalities. 11 further patients, with renal failure or gentamicin-resistant isolates, treated with aztreonam were all cured. Toxic effects were limited to symptomless liver-function-test abnormalities with aztreonam , whereas deterioration in renal function occurred in 4 gentamicin-treated subjects. Urinary colonisation with group D streptococci occurred in 14 of 46 aztreonam -treated patients (1 required treatment) compared with only 1 of 17 gentamicin-treated patients. 97% of 309 consecutive gram-negative urinary isolates tested, including 50 Pseudomonas aeruginosa, were susceptible in vitro to aztreonam and 91% to gentamicin. Aztreonam may prove an effective and safe alternative to the aminoglycosides.