Bacterial biofilms associated with implants remain a significant source of infections in dental, implant, and other healthcare industries due to challenges in biofilm removal. Biofilms consist of bacterial cells surrounded by a matrix of extracellular polymeric substance (EPS), which protects the colony from many countermeasures, including antibiotic treatments. Biofilm EPS composition is also affected by environmental factors. In the oral cavity, the presence of sucrose affects the growth of Streptococcus mutans that produce acids, eroding enamel and forming dental caries. Biofilm formation on dental implants commonly leads to severe infections and failure of the implant. This work determines the effect of sucrose concentration on biofilm EPS formation and adhesion of Streptococcus mutans, a common oral colonizer. Bacterial biofilms are grown with varying concentrations of sucrose on titanium substrates simulating dental implant material. Strategies for measuring adhesion for films such as peel tests are inadequate for biofilms, which have low cohesive strength and will fall apart when tensile loading is applied directly. The laser spallation technique is used to apply a stress wave loading to the biofilm, causing the biofilm to delaminate at a critical tensile stress threshold. Biofilm formation and EPS structures are visualized at high magnification with scanning electron microscopy (SEM). Sucrose enhanced the EPS production of S. mutans biofilms and increased the adhesion strength to titanium, the most prevalent dental implant material. However, there exists a wide range of sucrose concentrations that are conducive for robust formation and adhesion of S. mutans biofilms on implant surfaces.
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Targeting S. mutans biofilms: a perspective on preventing dental caries
The prevalence of biofilm diseases, and dental caries in particular, have encouraged extensive research on S. mutans biofilms, including methods of preventing its formation. Numerous small molecules with specific anti-biofilm activity against this pathogen have been isolated and synthesized. Generally, these molecules can be characterized into three categories: sucrose-dependent anti-adhesion, sucrose-independent anti-adhesion and cellular signaling interference. This review aims to provide an overview of the current small molecule strategies used for targeting S. mutans biofilms, and a perspective of the future for the field.
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- Award ID(s):
- 1755698
- NSF-PAR ID:
- 10194270
- Date Published:
- Journal Name:
- MedChemComm
- Volume:
- 10
- Issue:
- 7
- ISSN:
- 2040-2503
- Page Range / eLocation ID:
- 1057 to 1067
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Streptococcus mutans is a key pathogenic bacterium in the oral cavity and a primary contributor to dental caries. TheS. mutans Cid/Lrg system likely contributes to tolerating stresses encountered in this environment ascid and/orlrg mutants exhibit altered oxidative stress sensitivity, genetic competence, and biofilm phenotypes. It was recently noted that thecidB mutant had two stable colony morphologies: a “rough” phenotype (similar to wild type) and a “smooth” phenotype. In our previously published work, thecidB rough mutant exhibited increased sensitivity to oxidative stress, and RNAseq identified widespread transcriptomic changes in central carbon metabolism and oxidative stress response genes. In this current report, we conducted Illumina‐based genome resequencing of wild type,cidB rough, andcidB smooth mutants and compared their resistance to oxidative and acid stress, biofilm formation, and competence phenotypes. BothcidB mutants exhibited comparable aerobic growth inhibition on agar plates, during planktonic growth, and in the presence of 1 mM hydrogen peroxide. ThecidB smooth mutant displayed a significant competence defect in BHI, which was rescuable by synthetic CSP. BothcidB mutants also displayed reduced XIP‐mediated competence, although this reduction was more pronounced in thecidB smooth mutant. Anaerobic biofilms of thecidB smooth mutant displayed increased propidium iodide staining, but corresponding biofilm CFU data suggest this phenotype is due to cell damage and not increased cell death. ThecidB rough anaerobic biofilms showed altered structure relative to wild type (reduced biomass and average thickness) which correlated with decreased CFU counts. Sequencing data revealed that thecidB smooth mutant has a unique “loss of read coverage” of ~78 kb of DNA, corresponding to the genomic island TnSMU2 and genes flanking its 3′ end. It is therefore likely that the unique biofilm and competence phenotypes of thecidB smooth mutant are related to its genomic changes in this region. -
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Abstract Many bacterial pathogens express small G5 domains that exist in the context of various membrane‐anchored proteins and these G5 domains have been associated with colonization, cellular adhesion, and biofilm formation. However, despite over a decade since the computational prediction of these G5 domains, many remain uncharacterized, particularly those from
Streptococcus pneumoniae . Of five previously predicted G5 domains we found that four of these, all derived fromS. pneumoniae , are independently folded modules. As one of these exhibits extreme line broadening due to self‐association, we were able to use NMR solution studies to probe the potential ligand interactions of the remaining three G5 domains. None of these G5 domains engage N‐acetylglucosamine (NAG) as previously predicted but do interact with other small molecules that may modulate adherence to both bacteria and host cells. Specifically, while all G5 domains tested engage Zn, only one of these G5 domains engage heparin. NMR solution structural studies of the IgA1 Protease G5 (IgA1P‐G5) and endo‐beta‐N‐acetylglucosaminidase‐D G5 (ENDD‐G5) also facilitated identification of the ligand binding sites and confirm the typical G5 fold that comprises two connected β‐sheets with no canonical core. NMR relaxation experiments indicate flexibility on both ends and within the connecting regions between the β‐sheets. Our studies thus establish a basis for future biological experiments to test whether the ligands presented here are involved in bacterial adherence, either to bacteria or to host cells. -
An Overview of Biofilm Formation–Combating Strategies and Mechanisms of Action of Antibiofilm AgentsBiofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/c9md00015a
