Phenotypic and Genotypic Characterization of Glycopeptide, Aminoglycoside and Macrolide Resistance among Clinical Isolates of Enterococcus faecalis: a Multicenter Based Study

Background and Objectives: Enterococcus faecalis as the part of the normal floras of human gastrointestinal and genitourinary tracts are an important cause of nosocomial infections. The present study aimed to investigate the prevalence of genes encoding antimicrobial resistance and genetic relatedness of clinical isolates of E. faecalis among Iranian hospitalized patients. Materials and Methods: In this cross-sectional study during April 2017 to October 2017, a total of 232 E. faecalis isolates were obtained from different clinical specimens in four hospitals in Isfahan, the central part of Iran.E. faecalis isolates were identified by standard microbiologic tests and confirmed by specific PCR primers. Antimicrobial susceptibility testing was carried out by disk diffusion and E-test methods. The presence of antibiotic resistancegenes was determined by PCR method. The genetic relatedness among the isolates was assessed by ERIC-PCR. Results: Antibiotic susceptibility testing results indicated that 53 (22.8 %) out of 232 E. faecalisisolates were vancomycin resistant (MIC ≥ 256 μg/mL). All of the 53 vancomycin-resistant E. faecalisisolates carried the vanA andermB genes; whereas aac (6 )-Ieaph (2 ),ermA, and msrA gene were found in 94.3%, 28.3% and 3.8% of vancomycin-resistant isolates, respectively. ERIC-PCR typing revealed that 53vancomycin-resistantisolates were classified into 15 ERIC types. Conclusion: According to the results, the high level of resistance to gentamicin, erythromycin and vancomycin in enterococci isolates were mainly associated withthe presence of aac (6 )-Ieaph(2 ), ermB andvanA genes, respectively.Meanwhile, ERIC-PCR analysis demonstrated that the evaluated isolates were relatively heterogeneous.