Virulence Factors, Biofilm Formation and Antibiotic Resistance Pattern in Enterococcus faecalis and Enterococcus faecium, Isolated from Clinical and Commensal Human Samples in Isfahan, Iran

Background and Objectives: The aim of this study was to determine and compare antibiotic resistance profile, biofilm formation ability and frequency of agg and ace genes in Enterococcus spp strains, isolated from patients and healthy individuals. Materials and Methods: A total of 90 non-duplicate Enterococcus spp isolates were isolated from patients and healthy individuals. Antibiotic susceptibility pattern was determined by disk diffusion and E-test method. Virulence genes and two species of enterococci were determined by PCR amplification. The capacity of biofilm formation was also evaluated by microtiter plate technique. Results: E. faecalis was the predominant species among our clinical isolates (80%). The prevalence rates of agg and ace genes were 37.8% and 73.3% in clinical and 8.9% and 11.1% in healthy samples, respectively. The rate of Multiple Drug Resistant strains was 73.3% and 11.1% in clinical and healthy isolates, respectively. The ability of biofilm formation was significantly higher in clinical, compared to healthy isolates (100% vs 75.6%, P < 0.05). Conclusions: The frequency of ace and agg genes, antibiotic resistance and biofilm formation ability were significantly higher in clinical than in healthy isolates (P < 0.05). Existence of agg and ace genes, biofilm formation and antibiotic resistance among the healthy enterococci isolates has a special importance, because once these strains spread through clinical environments or reach water sources, it can be considered as a risk factor for health and sanitation of society.