title: Microstructural differences between single-species and dual-species biofilms of Streptococcus mutans and Veillonella parvula, before and after exposure to chlorhexidine.
abstract: Dual-species biofilms of Streptococcus mutans and Veillonella parvula are less susceptible to antimicrobials than single-species biofilms of the same microorganisms. The microstructure of single and dual-species biofilms of S. mutans and/or V. parvula was visualized to find out whether the spatial arrangement of bacteria in biofilms is related to survival strategies against antimicrobials. Biofilms were grown in glass-bottomed 96-well microtiter plates and exposed to chlorhexidine at 48 h. Fluorescent probes were used for staining. The microstructure of biofilms was analyzed by confocal scanning laser microscopy at 48, 96, 192, and 264 h. Spatial arrangement analysis was performed using DAIME software for 48 h biofilms. A decrease in the viability and thickness in all types of biofilms was detected after chlorhexidine treatment in time. In untreated biofilms, clustering was observed. In chlorhexidine-treated single-species biofilms, bacteria were dispersed. However, the most prominent clustering was observed in chlorhexidine-treated dual-species biofilm bacteria, which had a higher survival rate compared with chlorhexidine-treated single-species biofilms. Bacteria in dual-species biofilms establish a specific spatial arrangement, forming clusters within distances below 1.2 microm as a survival strategy against antimicrobials while the same bacteria lack this defensive construction in a single-species biofilm.
authors.affiliation: Department of Cariology, Endodontology, Pedodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and Free University, Amsterdam, The Netherlands. d.kara@acta.nl
authors.forename: Duygu
authors.initials: D
authors.lastname: Kara
authors.forename: Suzanne B I
authors.initials: SB
authors.lastname: Luppens
authors.forename: Jan
authors.initials: J
authors.lastname: van Marle
authors.forename: Rifat
authors.initials: R
authors.lastname: Ozok
authors.forename: Jacob M
authors.initials: JM
authors.lastname: ten Cate
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D002710:Chlorhexidine / Q000494:pharmacology*; D050296:Microbial Viability; D018613:Microscopy, Confocal; D013194:Staining and Labeling / Q000379:methods; D013295:Streptococcus mutans / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014678:Veillonella / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000900:Anti-Bacterial Agents; D002710:Chlorhexidine