Antibacterial efficacy of casein-derived peptides against Enterococcus faecalis.

BACKGROUND: The aim of this study was to test a casein peptide in its glycosylated form (kappa-casein glycopeptide, KCGP) and its non-glycosylated form (kappa-casein peptide, KCP) for antibacterial efficacy against Enterococcus faecalis in planktonic and biofilm cultures. METHODS: E. faecalis strain JKD 15036 was exposed to different concentrations of KCGP and KCP in a 96-well culture plate. The effect of the peptides on the growth of E. faecalis in planktonic culture was monitored by measuring optical density over 7 hours. Biofilm formation was measured after 24 hours using a crystal violet assay. All experiments were performed in triplicate. RESULTS: KCGP and KCP inhibited growth of E. faecalis in planktonic culture with no significant difference in activity between the peptides. KCGP at 0.16% w/v was significantly better at inhibiting E. faecalis biofilm formation than KCP at the same concentration and significantly better than NaOCl at 1.0% w/v. CONCLUSIONS: KCGP effectively inhibited E. faecalis biofilm formation and may have potential to augment the efficacy of traditional antiseptic agents.

The effect of ultrasonically activated irrigation on reduction of Enterococcus faecalis in experimentally infected root canals.

AIM: To investigate the ability of an ultrasonically activated irrigating system to eliminate bacteria from the canal wall and dentinal tubules of extracted teeth. METHODOLOGY: One hundred and thirty roots of intact human teeth were inoculated with Enterococcus faecalis for 4 weeks. The straight roots were randomly allocated to a baseline group (n=25) or subjected to routine cleaning and shaping procedures (n=105). Two sub-groups of prepared canals were then additionally exposed either to ultrasonic irrigation with 1% sodium hypochlorite (NaOCl) for 1 min (n=35) or to 1 week of intracanal medication with calcium hydroxide [Ca(OH)(2)] (n=35). All roots were processed for light microscopy (Brown and Brenn stain) (n=28) or scanning electron microscopy (n=7). Triplicate histological sections from each of the apical, middle and coronal thirds were scored for bacterial presence using pre-defined criteria. RESULTS: Baseline bacterial penetration resulted in an average depth of tubule invasion of 151 µm. Routine canal preparation failed to eliminate bacteria consistently from either the canal wall or within tubules. Ultrasonic irrigation and medication with Ca(OH)(2) consistently eliminated bacteria from the canal wall (P<0.001) compared with baseline and routine treatment, and more frequently from dentinal tubules than routine canal preparation alone (P<0.01). Ultrasonic irrigation was as effective in bacterial reduction as 1 week of intracanal medication with Ca(OH)(2), but neither led to complete bacterial elimination in all roots. CONCLUSIONS: Ultrasonically activated irrigation for 1 min with 1% NaOCl after canal preparation in straight root canals is potentially an effective supplementary step in microbial control.

Dentinal tubule invasion and adherence by Enterococcus faecalis.

AIM: To investigate dentinal tubule invasion and the predilection of Enterococcus faecalis for dentinal tubule walls. METHODOLOGY: The invasion of dentinal tubules in extracted human teeth by E. faecalis was measured ex vivo after 8 weeks of incubation. The canal walls of 16 root sections were either intact or instrumented with or without smear layer present. Extent and maximum depth of tubule invasion were assessed histologically and compared between groups. In the adherence study, 44 vertically split root samples were prepared to expose longitudinally aligned dentinal tubules and fractured orthodentine (OD). Surfaces were exposed to E. faecalis (erythromycin resistant strain, JH2-2 carrying plasmid pGh9:ISS1) and incubated aerobically for 2 h. Samples were processed for analysis using scanning electron microscopy. Bacterial adhesion to tubule walls versus fractured OD was calculated as number of cells per 100 microm(2). RESULTS: The strain of E. faecalis used in this study showed moderate to heavy tubule invasion after 8 weeks. In the adhesion studies, significantly more bacteria adhered to fractured OD than to dentinal tubule walls (ANOVA, P < 0.001). With respect to the tubule wall, adherence was greater in inner versus outer dentine (P = 0.02) and greater when bacterial adhesion was tested in chemically defined medium than in phosphate-buffered saline (ANOVA, P < 0.001). CONCLUSIONS: Although E. faecalis readily invaded tubules, it did not adhere preferentially to tubule walls. Initial colonization of dentinal tubules by E. faecalis may depend primarily on other factors.