title: beta-lactamase production by strains of Escherichia coli of intermediate susceptibility to beta-lactam antibiotics. A study of their clinical significance in urinary tract infection.
abstract: In a prospective study of patients treated with cephalexin or co-trimoxazole, almost all isolated E. coli strains of intermediate susceptibility to ampicillin or cephalosporin (MIC 2-16 microgram/ml) were shown to produce beta-lactamase detectable with a chromogenic cephalosporin substrate, or by the clover-leaf test or the acidimetric method. When assayed in preparations of sonicated bacteria, the enzyme had a cephalosporinase-substrate profile in a large majority of cases. In order to evaluate the clinical significance of this beta-lactamase production, 48 patients with urinary tract infection (UTI) were treated with cephalexin, an antibiotic hydrolysed by the enzyme. Forty-three additional patients were treated with co-trimoxazole for comparison. A statistically significant difference in cure rate (p less than 0.05) was found after 2 weeks. Six recurrences occurred in the cephalexin group and none in the co-trimoxazole group. However, after six weeks there were 8 and 5 recurrences, respectively (p less than 0.05). There were no differences in beta-lactamase activity or MIC/MBC between initial strains and isolates from recurrent UTI. Thus, the recurrent infections were not due to emergence of resistance.
mesh_terms: D000293:Adolescent; D000581:Amidohydrolases / Q000096:biosynthesis*; D000667:Ampicillin / Q000627:therapeutic use; D001424:Bacterial Infections / Q000188:drug therapy*; D001431:Bacteriological Techniques; D002506:Cephalexin / Q000627:therapeutic use*; D002510:Cephalosporinase / Q000096:biosynthesis*; D002986:Clinical Trials as Topic; D004338:Drug Combinations; D004341:Drug Evaluation; D004926:Escherichia coli / Q000201:enzymology*; D005260:Female; D006801:Humans; D008826:Microbial Sensitivity Tests; D010400:Penicillin G / Q000627:therapeutic use; D010403:Penicillin Resistance; D010405:Penicillinase / Q000096:biosynthesis*; D011446:Prospective Studies; D012008:Recurrence; D013420:Sulfamethoxazole / Q000627:therapeutic use*; D014295:Trimethoprim / Q000627:therapeutic use*; D014552:Urinary Tract Infections / Q000188:drug therapy*
chemical_list: D004338:Drug Combinations; D000667:Ampicillin; D014295:Trimethoprim; D000581:Amidohydrolases; D002510:Cephalosporinase; D010405:Penicillinase; D013420:Sulfamethoxazole; D002506:Cephalexin; D010400:Penicillin G