Frequency of inhibitor-resistant TEM β-lactamases in Escherichia coli isolates from urinary tract infections in Fran

Abstract

Over a six-month period in 1993, 2972 non-duplicated isolates of Escherichia coli causing urinary tract infections were collected in a French teaching hospital (n = 785) and in three private laboratories (n =2187). The resistance rate to amoxycillin-clavulanate combination (MIC > 16mg/l) was 25.0% in the hospital isolates and 100% in the community isolates. Respectively, 27.5% and 45.0% of hospital and community isolates resistant to amoxycillin-clavulanate exhibited an unusual β-lactam resistance pattern, suggesting inhibitor-resistant TEM (IRT) >-lactamase production. These isolates were highly resistant to amoxycillin-clavulanate (MIC₉₀ 1024 mg/L), but were susceptible to cephalosporins (MIC < 32 mg/L). Enzyme extracts of these IRT-producing strains focused at pi 5.2 (n = 100) or 5.4 (n = 53). DNA-DNA hybridization confirmed that the β-lactamases involved in this resistance mechanism were TEM-1 derived and contained variations in the altered positions described in IRT enzymes. This study shows a total frequency of 4.9% of IRT-producing isolates among E. coli isolated from urine specimens.