Comparison of biofilm-producing Enterococcus faecalis, Enterococcus faecium, and unusual Enterococcus strains

Abstract

The present study focused on determining the prevalence of biofilm-forming ability in Enterococcus faecalis , E. faecium , and unusual Enterococcus clinical isolates, and comparison of resistance and the prevalence of selected virulence factors among biofilm-positive strains. The ability to form biofilm was detected in 13.3% of E. faecalis , 90% of E. faecium , and 57.1% of unusual Enterococcus strains ( p =0.026). All E. faecalis strains were susceptible to β-lactams, while 37.5% of unusual and all E. faecium isolates were resistant to these antibiotics. Resistance to gentamicin was detected in 75% of E. faecalis , 55.5% of E. faecium , and 25% of other strains; resistance to streptomycin in 25%, 83.3%, and 50%, respectively. Analysis of the virulence revealed that the enterococcal surface protein ( esp ) gene was found in all E. faecium , 75.0% of E. faecalis , and 37.5% of other strains; collagen adhesin gene ( ace ) in 100%, 25.0%, and 37.5%; and hyaluronidase gene ( hyl ) in 83.3%, 0%, and 37.5%, respectively. Analysis of the resistance and virulence patterns showed that E. faecium isolates had the greatest variety of virulence and resistance determinants, while the lowest variety was exhibited by unusual strains. These findings indicate that unusual biofilm-producing Enterococcus strains have lower resistance and virulence potency than E. faecalis and E. faecium .