Basic Research-Technology
The Susceptibility of Starved, Stationary Phase, and Growing Cells of Enterococcus faecalis to Endodontic Medicaments

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Abstract

The purpose of this investigation was to compare the susceptibility of cells of Enterococcus faecalis during exponential growth, stationary phase and starvation phase to three endodontic medicaments. E. faecalis strains VP3-80 and A197A in different growth phases were exposed to saturated calcium hydroxide solution, 0.05% chlorhexidine digluconate and 0.0001% sodium hypochlorite. Cells in the exponential growth phase were the most sensitive to all three medicaments and were killed between 3 s and 10 min. Cells in stationary phase were more resistant and living cells could be recovered at 10 min. However, cells in starvation phase were the most resistant and were not totally eliminated by the medicaments during the 10-min test period. Number of surviving cells of E. faecalis cells to the tested medicaments increased 1000- to 10,000-folds in aging cultures.

Section snippets

Bacteria and Culture Conditions

The strains of E. faecalis used in this study were strain VP3-80 isolated from root filled tooth with chronic apical periodontitis in Lithuania (4) and strain A197A isolated from a case of persistent apical periodontitis in Finland (3). Cultures of the E. faecalis strains were grown overnight at 37°C on tryptic-soy-agar plates (TSA; Difco Laboratories, Detroit, MI). Identification of the strains has been described earlier by Sirén et al. (3) and Peciuliene et al. (8).

The growth curve was

Growth Curve

The amount of living cells increased exponentially during the first 6 h of incubation (exponential growth phase, Fig. 2). Between 6 and 24 h the amount of living cells remained stable (stationary phase); it decreased between 24 and 36 h and remained stable thereafter (starvation phase). The optical density measured at the respective time intervals increased during the first 12 h and remained unchanged thereafter.

Electrophoresis of E. faecalis Proteins

SDS-page patterns of proteins extracted from E. faecalis cells grown for 3, 12, and

Discussion

The main goal of the study was to test the susceptibility of bacterial cells in different physiological stages to three different disinfectants commonly used in endodontics. It was shown that the resistance of E. faecalis cells to the tested medicaments increased dramatically in aging cultures. Recent studies with E. faecalis have shown that cells growing in rich media are more susceptible to different types of stress than glucose-starved cells (24., 26.). There seems to be no corresponding

Acknowledgments

The authors thank Britt-Mari Kvam for technical assistance. The authors also thank Steinar Stølen and Renate Hars for the help with scanning and transmission electron microscopy.

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