Objective: Extended-spectrum beta-lactamases (ESBL) are frequently seen in Enterobacteriaceae species, especially Escherichia coli and Klebsiella pneumoniae. Treatment of infections caused by these bacteria is becoming even more challenging due to simultaneous co-resistance to amino-glycosides and fluoroquinolones. Thus, knowledge about the state of resistance is extremely important for appropriate empirical antibiotic treatment. This study was conducted to determine the antimicrobial susceptibility patterns and the rates of ESBL production in E. coli and K. pneumoniae strains isolated from the clinical specimens of hospitalized patients in our hospital.

Materials and Methods: A total of firstly grown isolates of 385 E. coli and 154 K. pneumoniae on the bacterial cultures of clinical specimens of consecutive patients hospitalized between January and December 2012 were analyzed, Strains isolated simultaneously from the other body sites of the same patients were excluded from the analysis. VITEK 2 automated system (bioMérieux, France) was used for bacterial identification, susceptibility testing, and detection of the presence of ESBL.

Results: In our study 212 (55%)out of 385 E. coli, and 86 (55.8%) out of 154 K. pneumoniae strains were found to produce ESBL. The resistance rates of ESBL-producing E. coli were 70.7% for ciprofloxacin, 74.0% for co-trimoxazole, 16.5% for amikacin, and 43.0% for gentamicin. The corresponding rates for ESBL-producing K. pneumoniae were 66.2, 68.6, 16.2, and 43%, respectively. Of ESBL-producing E. coli strains, 1.4% were resistant to imipenem, 2.8% to ertapenem, and 0.9% to meropenem. Among ESBL-producing K. pneumoniae strains, 10.51, 7, and 11.6% of isolates exhibited resistance to imipenem, meropenem, and ertapenem, respectively. Any resistant strain to colistin was not detected.

Conclusion: Among ESBL-producing E. coli and K. pneumoniae strains the lowest rates of resistance was seen against colistin and carbapenems.