Extended-Spectrum Beta-Lactamase Activity and In Vitro Efficiency of Ertapenem among Escherichia coli Strains Isolated from Urine Samples

Abstract

Introduction: Urinary tract infections are the most common infections among community and hospital-acquired infections. Escherichia coli is the most frequently isolated pathogen of these infections. Despite the widespread use of antibiotics, especially beta-lactamase and extended-spectrum beta-lactamase (ESBL) producing strains continue to increase in number. Since these strains have evolved antimicrobial resistance, morbidity and mortality rates and treatment costs are increasing. The aim of this study was to investigate ESBL activity of E. coli strains isolated from the urine samples sent to microbiology laboratory, and in vitro efficacy of ertapenem which recently entered the clinical use.

Materials and Methods: A total of 346 E. coli strains isolated from urinary specimens sent to clinical microbiology laboratory between September 2012 and September 2013 were included in the study. The samples were inoculated in 5% sheep blood agar and Eosin Methylene Blue Agar plates, and incubated in aerobic environment for 24-48 hours at 35 degrees C for routine examination. Besides conventional methods, VITEK 2 (bioMerieux, France) full automated system, was used for bacterial identification. Antibiotic sensitivity test of the identified bacteria was carried out by VITEK2 system, based on "Clinical and Laboratory Standards Institute (CLSI)" criteria.

Results: Seventy (20.2%) of 346 E. coli strains isolated from urine samples were found to be ESBL producer. Of these 97.4% were sensitive to ertapenem and all ESBL negative E. coli strains were found to be susceptible to ertapenem. About 12.9% of ESBL positive E. coli strains were ertapenem-resistant. When we comparec sensitivity to ertapenem in ESBL positive and negative strains, the difference was statistically significantly (p < 0.05).

Conclusion: Ertapenem is believed to be a good alternative of antimicrobial agent for the treatment of ESBL positive and negative E. coli infections with high sensitivity ratio and ease of single daily dose.