In vitro activity of four different antibiotics against extended-spectrum ?-lactamase producing Escherichia coli

Abstract

Objective: Urinary tract infections due to wide spectrum ß-lactamase (GSBL) producing Escherichia coli strains are especially seen with increasing prevalence and may lead to complications with treatment insufficiencies. In patients having risk factors for GSBL producing microorganism, the selection of an appropriate ampirical treatment is important in preventing the complications that may be seen. In this study, MIC (minimum inhibition concentration) values of GSBL producing E. coli strains' obtained from urine cultures, against tigecyclin, ertapenem, cefoperazone+ sulbactam (sulperazon) and levofloxacin antibiotics were aimed to be investigated. Method: In 2010, 87 GSBL producing E. coli strains isolated from urine cultures in TOBB ETÜ Hospital Clinical Microbiology Laboratory were identified with conventional methods. Antibiotic sensitivity tests were investigated by using Vitek-32 (BioMerieux, France). GBSL production of these strains was confirmed by double disc synergy test. Identified GSBL producing E.coli strains' MIC levels and sensitivities against antibiotics were investigated by using E- Test. Results: In GSBL producing E.coli strains, MIC of levofloxacin range of 0,01- >32 ?g/ml and MIC range of sulperazon were found to be MIC range 0.190-128 ?g/ml. MIC50 and MIC90 values of both antibiotics were found to be 12, ?32, 12, 32 ?g/ml. MIC range of tigecycline was found to be 0.190-25 ?g/ml and MIC50 and MIC90 values were found to be 0.50-1 ?g/ml, respectively. MIC range of ertapenem was found to be 0,004-0,75 ?g/ml and MIC50 and MIC90 values were found to be 0.047-0.250 ?g/ml, respectively. In our study, while no resistance against ertapenem was found, 1.15% resistance in tigecycline, 10.3% resistance and 18.4% intermediate MIC level was found in sulperazon, and also 24.1% sensitive and 75.9% resistant strains were determined in levofloxacin. Conclusion: Due to the 75.9% resistivity ration detected in levofloxacin; for patients especially at risk for infection development with GSBL producing strains, it will be appropriate not to prefer quinolons for empirical treatment selection. In the treatment of these strains, ertapenem and tigecycline are seen as active choices. Due to 10.3% resistance and 18.4% intermediate MIC value detected in sulperazon, it may be preferred in appropriate patients according to sensitivity results. In infections caused by GSBL producing E. coli strains; initiation of appropriate and effective empirical treatment to the patients with risk factors belonging to these infections is important in regard to prevent the complications that may form.