Molecular Characterization of High Level Vancomycin-resistant Enteroccus faecalis among Inpatientsat an Iranian University Hospital: Clonal Dissemination of ST6 and ST422

Background and Obgectives: Over the past two decades, Enterococci have emerged as an important opportunistic pathogen causing life-threatening infections in hospitals. Several virulence factors serve as adhesion and invasion agents for the pathogen which contribute to enhancing the pathogenesis and severity of enterococcal infections. Enteroccus faecalis is the most common and virulent species causing various infections. The purpose of the present study was to examine the prevalence of genes encoding virulence factor and molecular characterization of vancomycin-resistantE. faecalis strains isolated from hospitalized patients in Isfahan, thecentral city of Iran.Materials and Methods: A total of 53 vancomycin-resistantE. faecalis isolates (VREF) obtained from clinical samples of hospitalized patients were characterized by phenotypic and genotypic methods and 25 selected VREF isolates from internal and ICU wards were typed by multilocus sequence typing Results: The efa was most prevalent virulence gene (100%) among isolates, followed by gelE(92.45%), asa1(90.56%), ace (86.79%), esp (75.47%), cylA (39.62%), and hyl(18.86%). More than 80% of the isolates were HLGR. Multilocus sequence typing showed eight different sequence types including ST6, ST422, ST28, ST448, ST531, ST328, ST421, ST495.STs were grouped into two clonal complexes(CC) including CCA (ST6, ST422, ST448, ST531), CCF (ST28, ST421) and two singletons (ST328, ST495). Conclusion: Our data indicated a high prevalence of virulence genes among STs described in this study. In addition, the molecular analysis demonstrated ahigh genetic diversity among selected VREF strains from the ICU ward. Therefore, in order to prevent the colonization of virulent strains in the hospital environment, infection control procedures are highly recommended.