Antibiotic Resistance in Gram-Negative Bacteria Isolated From Blood Cultures

Objective: The aim of this study was to retrospectively determine the antimicrobial susceptibilities of Gram-negative bacteria isolated from blood cultures of hospitalized patients in 2012. Methods: Antibiotic resistance rates of isolated Gram-negative bacteria were evaluated retrospectively from patients' files. In this study, 106 Gram-negative bacteria isolated from patients' blood culture samples in intensive care units and clinical services were evaluated. Blood samples inoculated into BacT/Alert (R) FA Plus aerobic bottles and were followed in a fully automated blood culture device, BacT/Alert (R) 3D (bioMerieux, Marcy l'Etoile, France). The identification and antibiotic sensitivity tests of the isolated microorganisms were performed using automated VITEK (R) 2 (bioMerieux, Marcy l'Etoile, France) system and the results were evaluated according to the standards of Clinical and Laboratory Standards Institute (CLSI). Results: The most frequently isolated Gram-negative bacteria were Escherichia coli (37.7%), Klebsiella pneumoniae (22.6%), Pseudomonas aeruginosa (12.3%) and Acinetobacter baumannii (13.2%). Extended-spectrum beta-lactamase (ESBL) production was detected in 52.5% of E. coli and 83.3% of K. pneumoniae strains. The most effective antibiotics in vitro for ESBL producing and non-producing strains of both types were found as imipenem and meropenem. Resistance to antibiotics tested in ESBL-producing strains of E. coli was found to be significantly higher than non-ESBL-producing strains (p<0.05). In our study, aminoglycosides, particularly amikacin, was found to be the most effective agents for P. aeruginosa and A. baumannii strains. Imipenem and amikacin were found as most effective antibiotics for the Enterobacter spp. isolated in this study. Conclusions: All institutions should determine their microbial agent and antibiotic resistance profiles and establish their own antibiotic treatment policies and follow current guidelines for empirical antibiotherapy.