Enterococci are usually encountered and predominate in oral infections, especially those associated with dental root canal infections of necrotic pulp and periodontitis. This study aimed to detect and identify Enterococcus faecium isolated from infected root canals, using polymerase chain reaction ( PCR). Thirty samples were collected from patients with  necrotic pulp, infected root canals, and endodontic treatment failure, attending the Conservative Treatment Department, College of Dentistry, Mosul University, Dental Teaching Hospital. The samples were obtained by inserting sterile paper points into the root canals and transferred in brain heart infusion broth vials to be  inoculated in a selective M-Enterococcus Agar Base . Twenty five isolates that belong to the genus Enterococcus were   recognized by traditional culture methods and biochemical tests. Then, DNA extractions of these isolates were carried out for  identification  with PCR by the amplification of ddI (D-Ala-D-Ala Ligase) chromosomal genes of Enterococcus faecium. Among the 25  isolates, twenty (80%) were identified to the level of Enterococcus faecium by traditional culture methods and biochemical tests, in comparison to 17 (68%) identified by  molecular identification. The PCR products for the specific primer produced bands on agarose gel at the position of 658bp. The study showed that the use of PCR with primers for the E. faecium ddI gene may be the most accurate method for rapid identification of Enterococci. Molecular identification of Enterococcus spp. revealed a significant role of E. feacium in root canal infections. Also, the detection of ddI gene  using PCR provides a definitive target that could be used for the detection of E. faecium  from clinical samples.

This study aimed to show the enhanced effect of nanoparticles cobalt ferrite CoFe2O4 with chlorhexidine on Enterococcus faecium isolated from failure root canal treatment cases. Sol-gel technique was used to prepare the spinel cobalt ferrite CoFe2O4 at 200 °C then sintering at 400 °C & 600 °C, whereas the antimicrobial susceptibility test of nanoparticles was carried out according to the Kirby-Bauer technique compared with chlorhexidine. Fifteen isolates of Enterococcus faecium obtained by inserting sterile paper points in root canals, from patients who consulted the Teaching Hospital of Dentistry College at the University of Mosul, Iraq. For the first time, results showed that the nanoparticle cobalt ferrite CoFe2O4 at 400 °C and 600 °C, when mixed with chlorhexidine, give the mean inhibition zone 8.5334 mm and 8.0667mm respectively, while the pure chlorhexidine was providing a mean inhibition zone of 3.1667 mm, and also the nanoparticles cobalt ferrite in both cases of sintering without mixing, there was no antimicrobial effect. Statistical analysis using Duncan showed significant differences among groups (p < 0.05).