Evaluation of Virulence Factors and Plasmid-Related Transmissibility among Different Isolates of Enterococci

incidence of virulence factors among 114 Enterococcus faecalis and 35 Enterococcus faecium strains from different clinical specimens were compared with those isolated from control groups. A few of the isolates expressed two or more of the following traits simultaneously: hemolysin, aggregation substance, gelatinase, DNase, hemagglutinin and antibiotic resistance. The frequencies of hemolysin, aggregation substance, and gelatinase production in E. faecalis were much higher than those in E. faecium. However, no statistically significant differences were detected in the other traits. Two of the isolates showed total resistance to all of the antibiotics tested, and others displayed varied degrees of resistance pattern. The frequency of plasmid transfer was shown to be 10-4- 10-7 per donor among the isolated strains. The plasmid profile of the bacteria indicated that most of the isolates contained one or more plasmids with molecular weight ranging in 2 to 42 Mda regions. Resistance to gentamicin and tetracycline was the most observed antibiotic resistance pattern, and had the property of efficient inter-enterococcal spp. transfer by mating. Iran. Biomed.