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Growth at high pH increases Enterococcus faecalis adhesion to collagen
G Kayaoglu1, H Erten, D Ørstavik
1Department of Endodontics and Conservative Treatment, Faculty of Dentistry, Gazi University, Ankara, Turkey. guvenk@gazi.edu.tr
Insights
Alkaline conditions increase Enterococcus faecalis adherence to collagen, potentially explaining its persistence in root canals. Growth at higher pH enhances bacterial binding to collagen type I, but reduces binding to bovine serum albumin (BSA).
Area of Science:
- Microbiology
- Biochemistry
- Endodontics
Background:
- Enterococcus faecalis is a common pathogen in persistent endodontic infections.
- The role of environmental pH in E. faecalis virulence factors, such as adherence, is not fully understood.
Purpose of the Study:
- To investigate the impact of varying pH levels (7.1-9.5) on the in vitro adherence of Enterococcus faecalis to bovine serum albumin (BSA) and collagen type I.
Main Methods:
- Enterococcus faecalis strain A197A was cultured in media adjusted to pH levels between 7.1 and 9.5.
- Bacterial adherence to surfaces coated with BSA or collagen type I was quantified using crystal violet staining and spectrophotometry.
- Statistical analysis included the Kolmogorov-Smirnov test, Levene's test, and Student's t-test (alpha = 0.05).
Main Results:
- E. faecalis adherence to BSA decreased as the growth medium's alkalinity increased; bacteria grown at pH 7.1 showed significantly higher BSA binding.
- Conversely, bacterial adherence to collagen type I significantly increased for bacteria grown at pH 8.0 and 8.5 compared to pH 7.1.
Conclusions:
- A moderate increase in pH (up to 8.5) enhances the collagen-binding ability of E. faecalis.
- This increased collagen adherence may be a key factor in E. faecalis dominance in persistent endodontic infections, possibly linked to alkaline medicament use.
Aim:
To evaluate the effect of growth at pH levels from 7.1 to 9.5 on the adherence of Enterococcus faecalis to bovine serum albumin (BSA) and collagen type I.
Methodology:
Enterococcus faecalis strain A197A was grown in broth of adjusted pHs varying between 7.1 and 9.5. Aliquots of bacterial suspensions were added to wells coated either with BSA or with collagen type I. Bacteria adhering to the surfaces were stained with crystal violet. Spectrophotometric measurements of the dissolved stain were used to assess the number of bacteria adhering to the surfaces. The data obtained were analysed using the Kolmogorov-Smirnov test, Levene's test and Student's t-test, with alpha = 0.05 as the level for statistical significance.
Results:
The adhesion of E. faecalis to BSA-coated surfaces decreased inversely with alkalinity of the growth medium. The pH 7.1-grown bacteria bound to BSA significantly more than the other BSA groups. On the contrary, the adhesion to collagen type I-coated surfaces of bacteria grown at pH 8.0 and 8.5 was significantly greater than for those grown at pH 7.1.
Conclusions:
A minor increase in pH up to 8.5, which may be a consequence of insufficient treatment with alkaline medicaments such as calcium hydroxide, increases the collagen-binding ability of E. faecalis, in vitro. This can be a critical mechanism by which E. faecalis predominates in persistent endodontic infections.
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