Molecular epidemiology and antibiotic resistance patterns of Enterococcus faecalis isolates from hospitals in Tehran

Enterococcus faecalis is one of the most important causative agents of nosocomial infections. Control and prevention of these infections require appropriate epidemiological knowledge. This study investigated the correlation between molecular characteristics and drug resistance of E. faecalis isolates from local hospitals. A total of 125 isolates of Enterococcus faecalis from two hospitals in Tehran were identified by using culture and biochemical method. An antibiotic resistance assay was carried out by a disk diffusion method according to the Clinical and Laboratory Standards Institute guidelines. The genetic diversity of the strains was determined using a repetitive sequence-based polymerase chain reaction (REP-PCR) method. All isolates were typed by REP-PCR, and different PCR amplification products (from 9 to 17 amplified DNA fragments) were detected by gel electrophoresis. There were eight different PCR patterns (A-H), and a significant correlation was detected between the resistance to antibiotics and the obtained PCR patterns. The most relevant cases (28%) belonged to the fourth group (D). All group D isolates were resistant to tetracycline and quinupristin/dalfopristin. A high resistance to certain common antibiotics and clonal propagation were detected among isolates from patients in different wards of the hospitals. This study was the first to investigate E. faecalis isolates from Iranian patients and to describe patterns that showed correlation between infection prevalence and genetic origin/similarity of the isolates.