To determine the efficacy of aztreonam in the treatment of spontaneous bacterial peritonitis in patients with hepatic cirrhosis, 14 patients (7 males, 7 females) with 16 Gram-negative infective episodes (12 Escherichia coli and 4 Klebsiella pneumoniae) were treated with aztreonam infusions at doses of 1 gm per 8 hr for a planned 14-day period. Ages ranged from 40 to 75 years with a mean of 57 ± 10 years.

All organisms were highly susceptible to aztreonam (minimal inhibitory concentration ⩽ 0.06 to 0.12 μg per ml). Serum antibiotic levels were 61.9 ± 25.5 μg per ml (peak) and 27 ± 18.5 μg per ml (trough). Ascitic fluid antibiotic levels were 33.6 ± 22.5 μg per ml (peak) and 32.7 ± 16.8 μg per ml (trough).

Although the symptoms of infection were controlled within 3 days and ascitic fluid cultures became negative after 48 hr, 10 patients (62.5%) died, with hepatorenal syndrome and digestive tract hemorrhage as the principal causes of death. Three patients developed streptococcal superinfections during treatment; Streptococcus faecalis peritonitis in one case and spontaneous bacteremia due to Streptococcus equinus and Streptococcus mutans in the other two.

Aztreonam was well tolerated and clinically and bacteriologically efficacious in controlling the infection. Serum and ascitic fluid levels were considerably higher than the minimal inhibitory concentration for the causative organisms, suggesting that lower doses may achieve suitable therapeutic levels.

A negative aspect of the antibiotic therapy was the superinfections. The high mortality rate was attributable to the generally poor underlying condition of the patients.