Prevalence, Phenotype, and Genotype of Oral Enterococcus faecalis

Objectives: Enterococci are often recovered from root canals of failed endodontically treated teeth. It is believed that these species originate in the oral cavity, but data on oral prevalence of E. faecalis is inadequate. Therefore, the objectives of the present investigation were to study: (1) the oral prevalence of E. faecalis, (2) virulence characteristics associated with oral E. faecalis isolates, and (3) genetic profiles of oral E. faecalis. Methods: (1) Oral rinse samples were obtained from 80 patients attending an endodontic specialty clinic to determine the oral prevalence of E. faecalis. (2) Isolates recovered were subjected to phenotypic analyses: antibiotic susceptibility (E-test), heavy metals susceptibility (broth dilution), and bacteriocin, gelatinase and haemolysin activity. (3) Genetic profiles were obtained using two different typing methods: PFGE (pulsed-field gel electrophoresis) and plasmid analysis. Results: (1) Eighty patients attended the clinic for initial treatment (n=44), mid-treatment (n=18), retreatment (n=15) and recall (n=3). The overall oral prevalence of E. faecalis was 11.25% (n=9) with no significant difference in prevalance between treatment groups (p>0.05, Chi square). (2) All isolates except one were resistant to clindamycin. Haemolysin activity was found in three isolates and gelatinase activity in two isolates. One isolate (OR15) demonstrated bacteriocin, haemolysin and gelatinase activity as well as resistance to chloramphenicol, clindamycin, erythromycin, kanamycin and streptomycin, and intermediate susceptibility to tetracycline (MIC 12µg/mL). One isolate (OR17) was resistant to tetracycline (MIC 48µg/mL) and five isolates showed intermediate resistance to tetracycline (MIC 12-16µg/mL). There was no evidence of heavy metal resistance. (3) Molecular typing by PFGE and plasmid analyses revealed widespread genetic polymorphism. Conclusion: The data provide preliminary information on the genetic polymorphism and phenotypic diversity of E. faecalis recovered from the oral cavity.