Efficacy and safety of low dose aztreonam in the treatment of moderate to severe gram-negative bacterial infections.

One hundred and fifty-three patients with moderate to severe infections due to Gram-negative bacteria, including septicaemia (60 cases), lower respiratory tract infection (32 cases), intra-abdominal infection (40 cases) and urinary tract infection (21 cases), were treated with aztreonam 1 g every 12 h. This dosage is lower than usual. Criteria for inclusion included documented Gram-negative bacterial infections, and assessment of the severity of the disease by a scoring system for both community and hospital acquired infections. No other antibiotic active against Gram-negative bacteria was allowed. In 71 patients, in whom Gram-positive or anaerobic organisms were detected or suspected, additional agents effective against these organisms were administered. One hundred and forty-one patients (92.2%) were cured with a mean duration of treatment of 10.9 +/- 4.0 days. None of the Gram-negative bacteria initially isolated became resistant to aztreonam. Colonization, generally by a Gram-positive organism, was observed in 27 patients and superinfection in five. Aztreonam was well tolerated. This study suggests that a daily dosage of 2 g of aztreonam should be sufficient in the treatment of moderate to severe Gram-negative bacillary infections due to sensitive organisms.