[Detection of beta-lactamase-producing strains isolated from urinary tract and their drug susceptibility]

A total of 518 bacterial strains isolated from the urine of patients with various urological diseases in our Urological Department between November, 1987 and February, 1989 were studied for their beta-lactamase production and susceptibility to various antimicrobial agents was determined. beta-lactamase activity was determined by the acidometry disc method. There were 241 gram-positive cocci, 276 of gram-negative rods and 1 Neisseria gonorrhoeae. Thirty-four percent of the gram positive and 76.3% of gram negative rods produced beta-lactamase. S. aureus (81.3%), S. epidermidis (65.1%) in gram-positive cocci, E. cloacae (100%), S. marcescens (100%), C. freundii (100%), P. aeruginosa (97.2%), P. Rettgeri (88.9%), E. gergoviae (85.7%), K. oxytoca (84.6%), M. morganii (81.8%) and E. coli (69.0%) in gram-negative rods produced beta-lactamase at a higher rate. beta-lactamase produced by gram-positive cocci was entirely penicillinase, and that produced by gram-negative rods only penicillinase in 4.0%, only cephalosporinase in 44.2% and both in 25.4%. In S. aureus and S. epidermidis, the isolated rate of strains resistant to ampicillin (p less than 0.01) and piperacillin (p less than 0.05) in the beta-lactamase producing strains was significantly higher than that in the beta-lactamase non-producing strains. In E. coli, the isolation rate of strains resistant to ampicillin and piperacillin in the penicillinase-producing strains was significantly higher than in the penicillinase non-producing strains (p less than 0.01). But both cephalosporinase-producing strains and beta-lactamase non-producing strains showed high susceptibility to cephalothin. These results suggest that the penicillinase might present a clinical problem in the treatment of urinary tract infections by S. aureus, S. epidermidis and E. coli.