Phenotypic characteristics of enterococcus faecalis isolated from endodontic infections

Aim and objective: To evaluate the phenotypic characteristics of Enterococcus faecalis isolated from endodontic infections.
Background: Enterococcus faecalis is a microorganism detected in asymptomatic, persistent endodontic infections. E. faecalis has an ability to survive harsh environments including extreme alkaline pH.It resists bile salts, detergents, heavy metals, ethanol, azide & desiccation.E. faecalis endures prolonged period of nutritional deprivation. Enterococci can grow at10 C and 45 C at pH 9.6 in 6.5% NaCl broth and survive at 60 C for 30 minutes. This may explain its survival in root canal infections, where nutrients are scarce and there are limited means of escape from root canal medicaments.
Materials and methods: A total of 20 samples were collected from patients undergoing endodontic treatment. The samples were inoculated in Mac Conkey agar and brain heart infusion agar. Presumptive identification of Enterococci was done by Gram`s stain, Catalase test and Heat tolerance test in which Enterococci are gram positive cocci arranged in pairs. Brain-heart infusion agar (Oxoid) supplemented with 5% sheep blood was used for the detection of haemolytic activity. Gelatinase assay was carried out by adding an inoculum from a pure culture into tubes containing 12% gelatin in 0.8% nutrient broth.
Results: Cytolysin production was screened by cultivation on blood agar,2(10%) isolates produced complete (β) haemolysis,1(5%) isolate produced partial (α) haemolysis and the rest of the isolates did not produce haemolysis on blood agar (γ) haemolysis. Gelatinase assay by gelatin hydrolysis test revealed that 4(20%) of the isolates phenotypically expressed gelatinase gene as they could not liquefy gelatin media.