Morphological studies of Escherichia coli in the urine of patients with acute simple cystitis treated with aztreonam.

The effects of aztreonam (AZT) on the morphology of Escherichia coli in the urine of 5 patients with acute simple cystitis were studied by differential interference contrast microscopy. The urine specimens were collected via catheter before, 5, 15 and 30 minutes after intravenous administration of 1.0 gm AZT. The minimum inhibitory concentration of E. coli against AZT was 0.05 microgram/ml. The mean urinary concentrations at 5, 15 and 30 minutes after administration of AZT were 481.6 micrograms/ml, 1168.2 micrograms/ml and 993.4 micrograms/ml, respectively. In 4 patients, the urinalysis became normal within 30 minutes after the administration. Filamentous cells were observed at low and high urinary concentrations of AZT. They had vacuole-like formations. These findings were characteristic morphological changes caused by AZT. In the other patient, spheroplasts and ovoid cells were observed. AZT in the urine of patients with acute simple cystitis is suggested to have a high affinity for penicillin-binding protein (PBP) 3 and moderate affinity for PBP 1a.