Trend in Antibiotic Resistance of Extended-Spectrum Beta-Lactamase-Producing and Bloodstream Infections.

Objectives: Extended-spectrum beta-lactamases (ESBLs) have been detected more frequently in members of the family, particularly and . Infections caused by ESBL-producing bacteria are often resistant to treatment with various antibiotic classes and accompanied by increased complication risks, mortality, and costs. In this study, blood culture results were analyzed to determine the change in the ESBL production rate and antibiotic susceptibilities in and isolates over a period of 3 years.

Methods: The results of blood cultures sent to our laboratory between February 2014 and August 2016 were examined retrospectively. Repeat isolates from the same patient were not included when antibiotic susceptibility rates and clinical distributions were calculated. BD Bactec FX automated blood culture system (Becton Dickinson, Sparks, MD, USA) was used to examine the blood cultures. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (Bruker Daltonics, Bremen, Germany) was used to identify microorganisms. For antibiotic susceptibility tests (AST) and ESBL detection Kirby Bauer disk diffusion method or Phoenix automated system (Becton Dickinson, Sparks, MA, USA) was used. When the AST results were evaluated, Clinical and Laboratory Standards Institute breakpoints were used for 2014 and 2015, and European Committee on Antimicrobial Susceptibility Testing breakpoints were used for 2016.

Results: During the 3-year period, 224 (35%) of 632 and 137 (31%) of 439 isolates were determined to be ES BL-producers. The ESBL-positive isolate percentage for and for 2014, 2015, and 2016 was 23%, 36%, 48% and 23%, 32%, 37%, respectively. The increase in ESBL was statistically significant for both (p<0.001) and (p=0.011). ESBL-positive and strains were most sensitive to carbapenem-class antibiotics, amikacin, and colistin. While there was no meropenem-resistant strain, 5 (3.3%) ertapenem-resistant and 1 (0.7%) imipenem-resistant ESBL strains were detected. The ESBL strain resistance rate to ertapenem, imipenem, and meropenem was 12%, 11.2%, and 11.1%, respectively. The resistance rates of K. pneumonia strains to ertapenem, imipenem, meropenem, and piperacillin-tazobactam increased significantly over the study period (p<0.001).

Conclusion: Monitoring ESBL rates and the antibiotic susceptibility of and strains of bloodstream infections is of the utmost importance in guiding empiric antibiotic therapies and patient management.