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Resistance to acidic and alkaline environments in the endodontic pathogen Enterococcus faecalis
K Nakajo1, R Komori, S Ishikawa
1Division of Oral Ecology and Biochemistry, Department of Oral Biology, Tohoku University Graduate School of Dentistry, Sendai, Japan.
Oral Microbiology and Immunology
|August 23, 2006
Summary
Enterococcus faecalis exhibits superior acid and alkali resistance compared to oral streptococci, primarily due to enhanced membrane durability. These traits help explain its prevalence in challenging oral environments.
Area of Science:
- Microbiology
- Biochemistry
- Oral Health
Background:
- Enterococcus faecalis, a common endodontic pathogen, possesses mechanisms for acid and alkali resistance.
- Oral streptococci serve as a comparison group for understanding pH resistance strategies.
Purpose of the Study:
- To investigate the biochemical mechanisms of acid and alkali resistance in Enterococcus faecalis.
- To compare these mechanisms with those of representative oral streptococci, such as Streptococcus mutans and Streptococcus sanguinis.
Main Methods:
- Assessed acid and alkali resistance by examining bacterial growth across a pH range.
- Measured intracellular pH stability and cell membrane integrity using BCECF and SYTOX-Green assays.
- Compared E. faecalis with S. mutans and S. sanguinis under varying pH conditions.
Main Results:
- E. faecalis demonstrated growth from pH 4.0-11.0, outperforming S. mutans (pH 4.0-9.0) and S. sanguinis (pH 5.0-9.0).
- E. faecalis maintained intracellular pH stability across a wider extracellular pH range (2.5-12) compared to streptococci.
- The cell membrane of E. faecalis showed significantly higher durability against pH extremes.
Conclusions:
- Enterococcus faecalis exhibits greater alkali resistance and comparable acid resistance to Streptococcus mutans.
- Membrane durability and proton-transport systems are key factors in E. faecalis's pH resistance.
- These characteristics contribute to E. faecalis's success in acidic oral environments and persistent root canal infections.
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