Antimicrobial effect of probiotic bacteriocins on Streptococcus mutans biofilm in a dynamic oral flow chamber model – an in vitro study

ABSTRACT

Aim

To determine the antimicrobial activity of the bacteriocin-producing probiotic strains Streptococcus salivarius K12 and Streptococcus salivarius M18 alone or in combination against caries-associated Streptococcus mutans.

Methods

Antimicrobial activity of S. salivarius K12 and/or S. salivarius M18 against S. mutans ATCC 25175 growth and biofilm formation on hydroxyapatite (HA) discs was determined in a flow chamber model by recording the colony forming units (CFU/ml) after 48 h of co-cultivation. The biofilm was analyzed by scanning electron microscopy (SEM) and by confocal laser scanning microscopy (CLSM). Additionally, the simultaneous antagonism assay was used to assess the inhibitory effect of S. salivarius K12 and/or S. salivarius M18 against S. mutans ATCC 25175 and 21 clinical isolates of S. mutans.

Results

Co-cultivation of S. mutans and S. salivarius K12 and/or S. salivarius M18 led to the inhibition of S. mutans viability, thereby, preventing its biofilm formation on HA discs. Furthermore, S. salivarius K12 and S. salivarius M18 exhibited antimicrobial activity against most clinical isolates of S. mutans.

Conclusion

The in vitro flow chamber system used in this study allows the simulation of time-dependent administration of S. salivarius probiotic strains, either alone or in combination, to investigate the prevention of S. mutans biofilm formation in a standardized model.

KEYWORDS:

• Probiotics
• biofilm
• antibacterial therapy
• Streptococcus salivarius K12
• bacteriocin-like inhibitory substances
• Streptococcus salivarius M18
• Streptococcus mutans

Acknowledgments

Elisabeth Reichardt would like to thank Prof. Jeremy Burton (Western University, Michigan, US), Prof. Werner Reichardt (Ernst-Abbe-University of Applied Sciences, Jena, Germany) and Dr. Maximilian Ole Bahls (ETH Zürich, Switzerland) for substantial support during developing the project and writing the manuscript. The authors would also like to express their gratitude to the UZB laboratory team including Prof. Tuomas Waltimo, Dr. Irmgard Hauser-Gerspach, Dr. Monika Astasov-Frauenhoffer, Elisabeth Filipuzzi-Jenny, Hedwig Wariwoda and to Susanne Erpel from the Nano Imaging Lab (University of Basel).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conception and design, E.R.; data curation E.R., V.S., L.A.; data analysis and interpretation, E.R., V.S., E.K.; original draft preparation, review and editing, E.R., V.S., E.K., C.V. and M.M.B. All authors have read and agreed to the published version of the manuscript.

Ethical approval

Clinical isolates used in this study were collected from human volunteers and stored anonymously, in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki declaration. All volunteers were informed about the study and upon agreeing to participate, their consent was registered. Based on the Swiss Federal Law on Research Involving Humans (Swiss Human Research Act Regulations 810.30, HRA: https://www.fedlex.admin.ch/eli/cc/2013/617/de), formal ethical approval is not applicable for the research, which involves anonymised biological material.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/20002297.2024.2304971

Additional information

Funding

This work was supported by the Nakao Foundation; and the Swiss Dental Association (SSO) under [Grant number 328-21 to Elisabeth Reichardt].