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  • 1.
    Boisen, Gabriella
    et al.
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Davies, Julia R
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Neilands, Jessica
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Acid tolerance in early colonizers of oral biofilms2021In: BMC Microbiology, E-ISSN 1471-2180, Vol. 21, no 1, article id 45Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: In caries, low pH drives selection and enrichment of acidogenic and aciduric bacteria in oral biofilms, and development of acid tolerance in early colonizers is thought to play a key role in this shift. Since previous studies have focussed on planktonic cells, the effect of biofilm growth as well as the role of a salivary pellicle on this process is largely unknown. We explored acid tolerance and acid tolerance response (ATR) induction in biofilm cells of both clinical and laboratory strains of three oral streptococcal species (Streptococcus gordonii, Streptococcus oralis and Streptococcus mutans) as well as two oral species of Actinomyces (A. naeslundii and A. odontolyticus) and examined the role of salivary proteins in acid tolerance development.

    METHODS: Biofilms were formed on surfaces in Ibidi® mini flow cells with or without a coating of salivary proteins and acid tolerance assessed by exposing them to a challenge known to kill non-acid tolerant cells (pH 3.5 for 30 min) followed by staining with LIVE/DEAD BacLight and confocal scanning laser microscopy. The ability to induce an ATR was assessed by exposing the biofilms to an adaptation pH (pH 5.5) for 2 hours prior to the low pH challenge.

    RESULTS: Biofilm formation significantly increased acid tolerance in all the clinical streptococcal strains (P < 0.05) whereas the laboratory strains varied in their response. In biofilms, S. oralis was much more acid tolerant than S. gordonii or S. mutans. A. naeslundii showed a significant increase in acid tolerance in biofilms compared to planktonic cells (P < 0.001) which was not seen for A. odontolyticus. All strains except S. oralis induced an ATR after pre-exposure to pH 5.5 (P < 0.05). The presence of a salivary pellicle enhanced both acid tolerance development and ATR induction in S. gordonii biofilms (P < 0.05) but did not affect the other bacteria to the same extent.

    CONCLUSIONS: These findings suggest that factors such as surface contact, the presence of a salivary pellicle and sensing of environmental pH can contribute to the development of high levels of acid tolerance amongst early colonizers in oral biofilms which may be important in the initiation of caries.

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  • 2.
    Boisen, Gabriella
    et al.
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Prgomet, Zdenka
    Malmö University, Faculty of Odontology (OD). Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV).
    Enggren, Gabriela
    Malmö University, Faculty of Health and Society (HS), Department of Biomedical Science (BMV). Malmö University, Biofilms Research Center for Biointerfaces.
    Dahl, Hanna
    Malmö University, Faculty of Odontology (OD).
    Mkadmi, Cindy
    Malmö University, Faculty of Odontology (OD).
    Davies, Julia R
    Malmö University, Faculty of Odontology (OD). Malmö University, Biofilms Research Center for Biointerfaces.
    Limosilactobacillus reuteri inhibits the acid tolerance response in oral bacteria2023In: Biofilm, E-ISSN 2590-2075, Vol. 6, article id 100136Article in journal (Refereed)
    Abstract [en]

    Probiotic bacteria show promising results in prevention of the biofilm-mediated disease caries, but the mechanisms are not fully understood. The acid tolerance response (ATR) allows biofilm bacteria to survive and metabolize at low pH resulting from microbial carbohydrate fermentation. We have studied the effect of probiotic strains: Limosilactobacillus reuteri and Lacticaseibacillus rhamnosus on ATR induction in common oral bacteria. Communities of L. reuteri ATCC PTA5289 and Streptoccus gordonii, Streptococcus oralis, Streptococcus mutans or Actinomyces naeslundii in the initial stages of biofilm formation were exposed to pH 5.5 to allow ATR induction, followed by a low pH challenge. Acid tolerance was evaluated as viable cells after staining with LIVE/ DEAD & REG;BacLightTM. The presence of L. reuteri ATCC PTA5289 caused a significant reduction in acid tolerance in all strains except S. oralis. When S. mutans was used as a model organism to study the effects of additional probiotic strains (L. reuteri SD2112, L. reuteri DSM17938 or L. rhamnosus GG) as well as L. reuteri ATCC PTA5289 supernatant on ATR development, neither the other probiotic strains nor supernatants showed any effect. The presence of L. reuteri ATCC PTA5289 during ATR induction led to down-regulation of three key genes involved in tolerance of acid stress (luxS, brpA and ldh) in Streptococci. These data suggest that live cells of probiotic L. reuteri ATCC PTA5289 can interfere with ATR development in common oral bacteria and specific strains of L. reuteri may thus have a role in caries prevention by inhibiting development of an acid-tolerant biofilm microbiota.

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  • 3.
    Braathen, Gabriella
    et al.
    Malmö högskola, Faculty of Odontology (OD).
    Ingildsen, Viktor
    Malmö högskola, Faculty of Odontology (OD).
    Twetman, Svante
    Ericson, Dan
    Malmö högskola, Faculty of Odontology (OD).
    Jørgensen, Mette
    Presence of Lactobacillus reuteri in saliva coincide with higher salivary IgA in young adults after intake of probiotic lozenges2017In: Beneficial Microbes, ISSN 1876-2883, E-ISSN 1876-2891, Vol. 8, no 1, p. 17-22Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to compare the concentration of salivary immunoglobulin A (IgA) and the selected interleukins (IL)-1β, IL-6, IL-8 and IL-10 in young individuals with presence and non-presence of Lactobacillus reuteri in saliva after a three-week intervention with probiotic lozenges. The study group consisted of 47 healthy individuals aged 18-32 years with no clinical signs of oral inflammation. In a randomised, double-blind, placebo-controlled, cross-over trial participants ingested two lozenges per day containing two strains of the probiotic bacterium L. reuteri or placebo lozenges. The intervention and wash-out periods were three weeks. Stimulated and unstimulated whole saliva was collected at baseline and immediately after termination of the intervention periods. The samples were analysed for total protein, salivary IgA and selected cytokines. In this extended analysis, data were collected by analysing baseline and follow-up saliva samples related to ingestion of the probiotic lozenges for the presence of L. reuteri through DNA-extraction, PCR-amplification and gel-electrophoresis. At baseline, 27% of the individuals displayed presence of L. reuteri and 42% were positive immediately after the three-week probiotic intervention. Individuals with presence of L. reuteri in saliva had significantly higher (P<0.05) concentrations of salivary IgA and %IgA/protein at the termination of the probiotic intake compared with non-presence. No differences in the cytokine levels were observed. In conclusion, detectable levels of L. reuteri in saliva coincided with higher concentrations of salivary IgA and %IgA/protein in stimulated whole saliva after the three-week daily intake of probiotic lozenges. Our findings suggest that monitoring the presence of probiotic candidates in the oral environment is important to interpret and understand their possible immune-modulating role in maintaining oral health.

  • 4.
    Neilands, Jessica
    et al.
    Malmö University, Faculty of Odontology (OD).
    Svensäter, Gunnel
    Malmö University, Faculty of Odontology (OD).
    Boisen, Gabriella
    Malmö University, Faculty of Odontology (OD).
    Robertsson, Carolina
    Malmö University, Faculty of Odontology (OD).
    Wickström, Claes
    Malmö University, Faculty of Odontology (OD).
    Davies, Julia R
    Malmö University, Faculty of Odontology (OD).
    Formation and Analysis of Mono-species and Polymicrobial Oral Biofilms in Flow-Cell Models2023In: Bacterial Pathogenesis: Methods and Protocols,, Springer, 2023, p. 33-52Chapter in book (Refereed)
    Abstract [en]

    The oral microbiota, which is known to include at least 600 different bacterial species, is found on the teethand mucosal surfaces as multi-species communities or biofilms. The oral surfaces are covered with a pellicleof proteins absorbed from saliva, and biofilm formation is initiated when primary colonizers, which expresssurface adhesins that bind to specific salivary components, attach to the oral tissues. Further developmentthen proceeds through co-aggregation of additional species. Over time, the composition of oral biofilms,which varies between different sites throughout the oral cavity, is determined by a combination ofenvironmental factors such as the properties of the underlying surface, nutrient availability and oxygenlevels, and bacterial interactions within the community. A complex equilibrium between biofilm communities and the host is responsible for the maintenance of a healthy biofilm phenotype (eubiosis). In the faceof sustained environmental perturbation, however, biofilm homeostasis can break down giving rise todysbiosis, which is associated with the development of oral diseases such as caries and periodontitis.In vitro models have an important part to play in increasing our understanding of the complex processesinvolved in biofilm development in oral health and disease, and the requirements for experimental system,microbial complexity, and analysis techniques will necessarily vary depending on the question posed. In thischapter we describe some current and well-established methods used in our laboratory for studying oralbacteria in biofilm models which can be adapted to suit the needs of individual users. 

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