Investigation of Biofilm Formation of Enterococcus Species Isolated from Blood by Phenotypic and Genotypic Methods

Abstract

Objective: Enterococcus spp. are widely found in enviroment and can cause diseases. Although the factors that explain its virulence have not yet been fully clarified, enterococcal surface protein (esp) has been associated with the ability of biofilm formation in both Enterococcus faecalis and the Enterococcus faecium. In our study, it was aimed to determine the vancomycin resistance status of E. faecalis and E. faecium species and to investigate the presence of esp gene which is thought to be related of with polymerase chain reaction and biofilm formation capacity by phenotypic methods. Methods: A total of 170 Enterococcus spp. (E. faecalis n = 85, E. faecium n = 85) isolates that were isolated from blood culture were included in the study. Species identification was performed using conventional and automated methods. Vancomycin susceptibilities of isolates were determined by Kirby-Bauer disk diffusion method. Biofilm formation was evaluated phenotypically by using Tube and Microtitration plate methods. In all isolates, the presence of esp gene which is associated biofilms was investigated by polymerase chain reaction (PCR) method. Results: When the vancomycin susceptibilities of the strains included in the study were examined, it was found that 14 of the E. faecalis isolates (16.5%) were moderately susceptible and 1 of them was (1.2%) resistant. And 29 (34.1%) of E. faecium isolates were found to be resistant. It was determined that 5 strains (5.9%) were formed biofilm by tube method. By microtiter plate method, 27 (31.8%) tested strains were determined positive for biofilm formation. The 5 isolates which were positive by tube method also found positive by microtiter plate method. All strains that were positive in both phenotypic methods were found to be E. faecalis. And 49 (57.6%) E. faecalis and 20 (23.5%) E. faecium strains were found positive esp. When the genotypic method was compared with phenotypic methods, 24 isolates which were found positive by microtiter plate method and 5 isolates which were found positive by tube method, were found positive for esp gene. Conclusion: According to these results, E. faecalis isolates are thought to have higher biofilm formation capacity than E. faecium. Furthermore, it is thought that the esp gene may be related to biofilm formation but the presence of esp alone is not sufficient for biofilm formation. New and comprehensive studies on the subject will be able to provide new and useful data on the role of biofilm formation in the virulence of enterococci. © 2021. All Rights Reserved.