In vitro alkaline pH resistance of Enterococcus faecalis

Area of Science:

• Microbiology
• Endodontics
• Dental Materials Science

Background:

• Enterococcus faecalis is a prevalent bacterium in failed endodontic treatments.
• Alkaline agents are standard in endodontics due to biocompatibility and antimicrobial properties.
• E. faecalis exhibits resistance to alkaline environments, posing a challenge in root canal disinfection.

Purpose of the Study:

• To investigate the in vitro alkaline pH resistance of Enterococcus faecalis.
• To determine the time required for alkaline conditions to inhibit E. faecalis growth.
• To evaluate the survival of clinical E. faecalis isolates at extreme pH levels.

Main Methods:

• Clinical isolates of E. faecalis and a reference strain were exposed to pH levels of 9.5, 10.5, 11.5, and 12.5.
• Bacterial growth was monitored via turbidity and confirmed by culturing on M-Enterococcus agar over 14 days.
• pH stability of the broth and bacterial acidification potential were assessed.

Main Results:

• All E. faecalis strains grew at pH 9.5 to 11.5 throughout the study period.
• At pH 12.5, bacterial growth was observed for up to 48 hours, with 13 strains growing at 24 hours and 2 strains at 48 hours.
• No growth occurred at pH 12.5 after 72 hours of incubation, indicating bacterial death.

Conclusions:

• Enterococcus faecalis possesses significant resistance to highly alkaline environments.
• Extended exposure (72 hours) at pH 12.5 is necessary to eradicate some clinical E. faecalis isolates.
• Findings suggest current alkaline endodontic treatments may require optimization for complete bacterial elimination.