Antimicrobial Resistance Patterns of Enterococcus faecalis and Enterococcus faecium Bacteria Isolated from Bloodstream Infections

Abstract

Introduction: Enterococci have recently become one of the most common causes of nosocomial bloodstream infections. Today, these bacteria account for about 10% of all bacteria. This study aimed to determine the rates of resistance to antibiotics that are commonly used in the treatment of Enterococcus faecalis and Enterococcus faecium strains isolated from nosocomial bloodstream infections. Materials and Methods: The study included the E. faecalis and E. faecium strains isolated from bloodstream infections at the Practice and Research Hospital of the Faculty of Medicine, Cumhuriyet University over a total period of four and a half years between (January 2009 and June 2013). Strain typing and antimicrobial sensitivity testing were performed using an automated system (BD, Phoenix, AZ, USA) according to the guidelines of the Clinical and Laboratory Standards Institute. Nosocomial bloodstream infection diagnosis was based on the diagnostic criteria of the Centers for Diseases Control and Prevention. Results: One hundred and three enterococci strains were isolated from nosocomial bloodstream infections during the study period. 51 (49.5%) of these strains were typed as E. faecalis and 52 (50.5%) as E. faecium. While there were 44 (84.6%) ampicillin-resistant strains among E. faecium isolates, this number was 2 (3.9%) (p= 0.001) among E. faecalis strains. High-level aminoglycoside resistance rate (500 µg/mL) was higher among E. faecium isolates compared with E. faecalis isolates (63.5% vs. 33.3%; p= 0.002). While no linezoid or daptomycin resistance was noted among the strains, only 2 (1.9%) of a total of 103 enterococci strains were found to be resistant to both vancomycin and teicoplanin. Conclusion: Problems caused by the resistance of nosocomial pathogens to antimicrobials are rapidly increasing. Therefore, clinical centers should constantly update and share their available data in relation to drug resistance. We consider that the local findings of this study, conducted at a university hospital, can be used particularly in fighting against nosocomial enterococcal infections to contribute to the formation of successful empirical treatment models