Evaluation of antibiotic susceptibility in enterococci isolated from blood culture samples

Abstract

Aims: Increased vancomycin resistance in enterococci is an important cause of life-threatening bloodstream infections in hospitalized patients. The aim of this study is to determine the antibiotic susceptibility rates of Enterococcus strains isolated from blood cultures in hospitalized patients in Antalya Training and Research Hospital. 
 Methods: The antibiotic resistance rates of Enterococcus strains isolated from blood cultures of patients hospitalized in the service and intensive care units (ICU) between 1 January 2018 and 30 December 2022 were examined retrospectively. Blood samples were studied with the BacT/ALERT 3D culture system (Biomerieux, France). Bacterial identification was performed using conventional methods, Matrix Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometer (MALDI-TOF MS) and VITEK 2 (Biomerieux, France) systems. Antimicrobial susceptibility tests were performed with VITEK 2 (Biomerieux, France) systems. Ampicillin, vancomycin, teicoplanin, high-level gentamicin resistance (HLGR) and linezolid susceptibility of isolated strains were evaluated according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Vancomycin minimal inhibitory concentration (MIC) values of vancomycin resistant strains were studied by microdilution gradient strip test (Bioanalyse).
 Results: A total of 623 strains of enterococci were isolated from blood culture samples. Of the enterococci, 305 (48.9%) were identified as Enterococcus faecalis, 281 (45.6%) Enterococcus faecium, 12 (1.9%) Enterococcus avium, 11 (1.8%) Enterococcus gallinarum, 7 (1.2%) Enterococcus casseliflavus, 2 (0.4%) Enterococcus durans and 1 Enterococcus hirae (0.2%). Ampicillin and HLGR resistance rates of isolated E. faecalis strains were 11 (3.6%) and 72 (23.6%), respectively, and all strains were found to be susceptible to vancomycin, teicoplanin and linezolid. The ampicillin, vancomycin, teicoplanin and HLGR resistance rates of E. faecium strains were determined as 229 (81.5%), 36 (12.8%), 30 (10.7%) and 142 (50.5%), respectively, and all strains were found to be susceptible to linezolid. 
 Conclusion: In infections caused by enterococci, identification and determination of antibiotic susceptibility rates according to culture antibiogram results would be the right approach. Knowing the current susceptibility rates of enterococci isolated from blood culture samples in our hospital will contribute for clinicians' planning of empirical treatment.