Investigation of virulence factors of Enterococcus faecalis strains isolated in secondary/ persistent infections

Abstract

Objective: More virulent strains may result from  the acquisition of genes by genetic exchange,  pathogenicity islands in several species encoding  toxins, adhesion factors and other factors associated  with virulence. The aim of this study was to investigate  the prevalence of E. faecalis strains in secondary  endodontic/ persistent using endodontic infection by  culture and PCR technqiues; and to investigate for  the presence of virulence factor genes of gelatinase  (gelE), cytolysin activator (Cyla), surface adhesin  of Enterococcus (ESP) and collagen adhesin of  Enterococcus (ACE). Material and methods: Microbial samples were obtained from 12 teeth with  secondary/ persistent endodontic infection showing  apical periodontitis. Culture techniques were used  including serial dilution, plating, incubation, and  biochemical identification. For PCR detection, samples  were analyzed using a species-specific primer of the  16S rDNA and the downstream intergenic spacer  region. Results: Culture and PCR detected the test  species in 3/12 (25%) and 5/12 (41.6%) of teeth,  respectively. A total of 38 Enterococcus faecalis strains  were isolated and submitted to the virulence factor  genes analysis. PCR products consistent with genes  encoding surface adhesion (ESP), gelatinase (gelE)  and collagen binding antigen (ACE) were found in  26/38 (68%), 31/38 (81%) and 38/38 (100%) of  the isolates. The Cytolysin activator (Cyla) gene was  not recovered from E. faecalis isolates. Conclusions:  In conclusion, the present study revealed by culture  and molecular methods revealed a high prevalence  of E. faecalis in teeth with secondary/ persistent  endodontic infection. Moreover, of a clinical  relevance, we found different E. faecalis strains  carrying different virulence determinants.

KEYWORDS Bacteria; E. faecalis; Root canal, virulence.