Patterns of Resistance to Beta-Lactams and Characterization of Beta-Lactamases in Escherichia coli Isolates from Children in Tunisia

AbstractSeventy-six (75.2%) of 101 Escherichia coli isolates, collected over a 2-month period in 2002 at the Children's Hospital of Tunis (Tunisia), were resistant to at least one beta-lactam. They produced beta-lactamases which were further characterized by spectrophotometry, isoelectric focusing (IEF) and PCR. Seventy-five isolates had a pI 5.4 beta-lactamase and one isolate expressed a pI 5.6 beta-lactamase. These beta-lactamases were active against penicillins and cephalothin. Nineteen of 76 isolates were resistant to ticarcillin-clavulanic acid combination. The bla TEM gene was detected in 71 isolates, all expressed a pI 5.4 beta-lactamase that was assumed to be TEM-1 or inhibitor-resistant TEM (IRT). Thirty-eight of 76 isolates showed one weak band on IEF with pIs ranging from 8.2 to ≥9, suggesting low level expression of the chromosomal AmpC beta-lactamase. Five of 76 isolates produced extended-spectrum beta-lactamases (ESBLs), with a basic pI of 7.9 or 8.7, active on penicillins, extended-spectrum...