[Antibacterial activity of aztreonam against clinical isolates]

To evaluate the antibacterial activity of a monobactam antibiotic, aztreonam (AZT), MICs of AZT and other antibiotics against clinical isolates collected at 36 participating institutions after January 1992 were determined using the agar plate dilution method (size of inoculum, 10(6) cfu/ml) according to the Japan Society of Chemotherapy standard. The antibiotics that were tested along with AZT included piperacillin (PIPC), cefoperazone (CPZ), and amikacin (AMK). AZT was found to be more active against Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Proteus vulgaris, Morganella morganii, and Providencia rettgeri than CPZ, PIPC, and AMK. AZT was also more active against Serratia marcescens than the other antibiotics, but about 6% of the strains tested were resistant to AZT with MIC of 12.5 micrograms/ml. Against Enterobacter cloacae and Citrobacter freundii, however, was more active AMK than AZT. AZT showed a normal activity distribution with a single peak at the MIC of 3.13-6.25 micrograms/ml against Pseudomonas aeruginosa, and 35% of inoculum was resistant with high MIC values (MIC > or = 25 micrograms/ml). Activities of AZT against Haemophilus influenzae and Neisseria gonorrhoeae were comparable to those of CPZ.