Susceptibility of clinical isolates to aztreonam

Aztreonam (AZT), which has a newly developed and synthetic structure belonging to the group of monobactams, possesses excellent antibacterial activity against a broad range of Gram-negative bacteria (including the beta-lactamase producing strains). Antibacterial activities of AZT were examined and compared with those of 5 antibiotics (cefoperazone (CPZ), latamoxef (LMOX), cefotaxime (CTX), cefmetazole (CMZ) and cefsulodin (CFS) against 296 strains of clinical isolates. The evaluation of antibacterial activities was determined with the inhibition zone diameter obtained by the single disc method. The results can be summarized by three categories as follows: 1. Susceptibility of clinical isolates to AZT and other antibiotics AZT and other 3rd-generation antibiotics (CPZ, LMOX, CTX) showed excellent antibacterial activities against most strains. Especially AZT was more active against Enterobacter cloacae and Serratia marcescens than reference drugs. Against Pseudomonas aeruginosa, the activity of AZT was similar to that of CFS. AZT showed as excellent activity against P. aeruginosa as CFS. 2. Susceptibility of strains isolated from different clinical materials and different clinics AZT showed the highest antibacterial activity against the clinical isolates from sputum, pharynx, urine, pus, bile, puncture fluid, blood and others. AZT exhibited the most potent activity against isolates in the 7 clinics we tested. 3. Susceptibility of strains isolated from inpatients and outpatients AZT demonstrated the highest antibacterial activity (the rate of susceptibility: 87.0%) against strains obtained from inpatients (except for P. aeruginosa). The activity of AZT (81.4%) against P. aeruginosa was as active as that of CFS (81.4%), and it was the highest in all drugs. Antibacterial activity of these antibiotics against bacteria was rated as follows: AZT greater than LMOX greater than CPZ greater than CTX greater than CMZ AZT showed the highest antibacterial activity (100%) against strains isolated in all the materials and at all the clinics tested of outpatients. Antibacterial activity of these antibiotics against isolates from outpatients was rated as follows: AZT greater than CPZ greater than LMOX greater than CTX greater than CMZ.