Response to alkaline stress by root canal bacteria in biofilms

Response to alkaline stress by root canal bacteria in biofilms
Published article online:
27 Feb 2007
Issue online:
24 Apr 2007
Received 9 August 2006; accepted 18 October 2006
To cite this article: L. E. Ch?vez de Paz, G. Bergenholtz, G. Dahl»n, G. Svensâter (2007)
Response to alkaline stress by root canal bacteria in biofilms
International Endodontic Journal 40 (5), 344Ò355.
doi:10.1111/j.1365-2591.2006.01226.x
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L. E. Ch?vez de Paz11Department of Oral Biology, Faculty of Odontology, Malmà University, Malmà, Sweden, G. Bergenholtz22Department of Endodontology, G. Dahl»n33Department of Oral Microbiology, Faculty of Odontology, The Sahlgrenska Academy at Gàteborg University, Gàteborg, Sweden & G. Svensâter11Department of Oral Biology, Faculty of Odontology, Malmà University, Malmà, Sweden

Dr Luis Eduardo Ch?vez de Paz Villanueva, Department of Oral Biology, Faculty of Odontology, Malmà University, SE-205 06 Malmà, Sweden (Tel.: +46 40 6658659; e-mail: luis.chavez.de.paz@od.mah.se).
Ch?vez de Paz LE, Bergenholtz G, Dahl»n G, Svensâter G. Response to alkaline stress by root canal bacteria in biofilms. International Endodontic Journal, 40, 344Ò355, 2007.

Abstract

Aim To determine whether bacteria isolated from infected root canals survive alkaline shifts better in biofilms than in planktonic cultures.

Methodology Clinical isolates of Enterococcus faecalis, Lactobacillus paracasei, Olsenella uli, Streptococcus anginosus, S. gordonii, S. oralis and Fusobacterium nucleatum in biofilm and planktonic cultures were stressed at pH 10.5 for 4 h, and cell viability determined using the fluorescent staining LIVE/DEAD BacLight bacterial viability kit. In addition, proteins released into extracellular culture fluids were identified by Western blotting.

Results Enterococcus faecalis, L. paracasei, O. uli and S. gordonii survived in high numbers in both planktonic cultures and in biofilms after alkaline challenge. S. anginosus, S. oralis and F. nucleatum showed increased viability in biofilms compared with planktonic cultures. Alkaline exposure caused all planktonic cultures to aggregate into clusters and resulted in a greater extrusion of cellular proteins compared with cells in biofilms. Increased levels of DnaK, HPr and fructose-1,6-bisphosphate aldolase were observed in culture fluids, especially amongst streptococci.

Conclusions In general, bacteria isolated from infected roots canals resisted alkaline stress better in biofilms than in planktonic cultures, however, planktonic cells appeared to use aggregation and the extracellular transport of specific proteins as survival mechanisms.

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