Isothermal microcalorimetry provides new insights into biofilm variability and dynamics

Authors

  • Monika Astasov-Frauenhoffer,

    Corresponding author
    • Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Basel, Switzerland
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  • Olivier Braissant,

    1. Laboratory of Biomechanics and Biocalorimetry, c/o Biozentrum/Pharmazentrum, University of Basel, Basel, Switzerland
    2. Department of Urology, University Hospital Basel, Basel, Switzerland
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  • Irmgard Hauser-Gerspach,

    1. Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Basel, Switzerland
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  • Alma U. Daniels,

    1. Laboratory of Biomechanics and Biocalorimetry, c/o Biozentrum/Pharmazentrum, University of Basel, Basel, Switzerland
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  • Roland Weiger,

    1. Clinic for Periodontology, Endodontology and Cariology, University of Basel, Basel, Switzerland
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  • Tuomas Waltimo

    1. Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Basel, Switzerland
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Correspondence: Monika Astasov-Frauenhoffer, Institute of Preventive Dentistry and Oral Microbiology, School of Dental Medicine, University of Basel, Hebelstrasse 3, 4056 Basel, Switzerland. Tel.:+41 (0)61 267 25 98; fax: +41 (0)61 267 26 58; e-mail: m.astasov-frauenhoffer@unibas.ch

Abstract

The purpose of this study was to investigate a three-species in vitro biofilm with peri-implantitis-related bacteria for its variability and metabolic activity. Streptococcus sanguinis, Fusobacterium nucleatum, and Porphyromonas gingivalis were suspended in simulated body fluid containing 0.2% glucose to form biofilms on polished, protein-coated implant-grade titanium disks over 72 h using a flow chamber system. Thereafter, biofilm-coated disks were characterized by scanning electron microscopy and fluorescence in situ hybridization/confocal laser scanning microscopy. To assess metabolic activity within the biofilms, their heat flow was recorded for 480 h at 37 °C by IMC. The microscopic methods revealed that the total number of bacteria in the biofilms varied slightly among specimens (2.59 × 104 ± 0.67 × 104 cells mm−2), whereas all three species were found constantly with unchanged proportions (S. sanguinis 41.3 ± 4.8%, F. nucleatum 17.7 ± 2.1%, and P. gingivalis 41.0 ± 4.9%). IMC revealed minor differences in time-to-peak heat flow (20.6 ± 4.5 h), a trend consistent with the small variation in bacterial species proportions as shown by microscopy. Peak heat flow (35.8 ± 42.6 μW), mean heat flow (13.1 ± 22.0 μW), and total heat over 480 h (23.5 ± 37.2 J) showed very high variation. These IMC results may be attributed to differences in the initial cell counts and relative proportions of the three species, their distribution and embedment in exopolysaccharide matrix on the test specimens. The present results provide new insights into variability and dynamics of biofilms on titanium disks, aspects that should be explored in future studies of dental surfaces.

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