A comparative study of the effect of probiotics on cariogenic biofilm model for preventing dental caries

Dental caries is induced by oral biofilm containing Streptococcus mutans. Probiotic bacteria were mainly studied for effect on the gastrointestinal tract and have been known to promote human health. However, the information of probiotics for oral health has been lack yet. In this study, we investigated influence of various probiotics on oral bacteria or cariogenic biofilm and evaluated candidate probiotics for dental caries among them. The antimicrobial activity of the spent culture medium of probiotics for oral streptococci was performed. Probiotics were added during the biofilm formation with salivary bacteria including S. mutans. The oral biofilms were stained with a fluorescent dye and observed using the confocal laser scanning microscope. To count bacteria in the biofilm, the bacteria were plated on MSB and BHI agar plates after disrupting the biofilm and cultivated. Glucosyltransferases (gtfs) expression of S. mutans and integration of lactobacilli into the biofilm were evaluated by real-time RT-PCR. Among probiotics, Lactobacillus species strongly inhibited growth of oral streptococci. Moreover, Lactobacillus species strongly inhibited formation of cariogenic biofilm model. The expression of gtfs was significantly reduced by Lactobacillus rhamnosus. The integration of L. rhamnosus into the biofilm model did not exhibit. However, L. acidophilus and L casei integrated into the biofilm model. These results suggest that L. rhamnosus may inhibit oral biofilm formation by decreasing glucan production of S. mutans and antibacterial activity and did not integrate into oral biofilm, which can be a candidate for caries prevention strategy.     

Antimicrobial Effects of Peptides from Human Beta-Defensin-3 on Planktonic and Biofilm States of Streptococci

Human beta-defensin-3 (hBD3) acts as a first line of defense against both Gram-positive and Gram-negative bacteria infection. Streptococci are the significant cause for oral biofilm associated diseases. We synthesized three fragments (hBD3-1, hBD3-2, hBD3-3) from the hBD3 and evaluated the antibacterial efficacy on oral streptococci. All of the three fragments from hBD3 had good estimated solubility and hBD3-3 had a higher net positive charge than others. Structure analysis showed that the three fragments shared stable β-sheet structure, but tyrosine were not found in hBD3-2 and hBD3-3 by using Raman and circular dichroism spectroscopy. The inhibition ability of the peptides was examined on the bioactivity of Streptococcus oralis (S.oralis), Streptococcus sanguinis (S. sanguinis) and Streptococcus gordonii (S. gordonii) by minimal inhibitory concentration, minimum bactericidal concentration and anti-biofilm formation test. Three fragments had antimicrobial activity on planktonic state of streptococci, and S. oralis had much more sensitive to the three peptides. Results of antibiofilm experiment showed that streptococci biofilm formation was more sensitive to hBD3-3. Confocal laser scanning microscopy and scanning electron microscopy showed the decrease of biomass and bacterial morphology destruction, which indicated that the antimicrobial mechanism of hBD3-3 might involve an electrostatic charge-based impact on membrane permeability. In conclusion, hBD3-3 possessed the potential capacity for depressing the growth of bacteria, especially first colonizers during the development of oral biofilm. Powerful, endogenous antimicrobial peptide provides the potential to interfere with biofilm by disorganizing early biofilm formation and thereby inhibiting biofilm-associated diseases.     

Prevention of biofilm formation on titanium surfaces modified with conjugated molecules comprised of antimicrobial and titanium-binding peptides

Specific binding of antimicrobial peptides to titanium (Ti) surfaces may serve to prevent biofilm formation, leading to a reduction in peri-implantitis. This study evaluated the binding behavior of conjugated molecules consisting of antimicrobial and hexapeptidic Ti-binding peptides (minTBP-1) using the quartz crystal microbalance (QCM-D) technique, and investigated the effect of modification of Ti surfaces with these peptides on the bioactivity of Porphyromonas gingivalis. Four kinds of peptide were prepared: histatin 5 (DSHAKRHHGYKRKFHEKHHSHRGY), minTBP-1 + histatin 5 (RKLPDAPDSHAKRHHGYKRKFHEKHHSHRGY), lactoferricin (FQWQRNMRKVR), and minTBP-1 + lactoferricin (RKLPDAPGGFQWQRNMRKVR). The QCM-D analysis demonstrated that significantly larger increases in peptide adsorption were observed in the conjugated peptides than in antimicrobial peptides alone. In addition, ATP activity in P. gingivalis in peptide-modified specimens significantly decreased compared to that in the Ti control. These results indicate that surface modification with conjugated molecules consisting of antimicrobial and Ti-binding peptides is a promising method for reduction of biofilm formation on Ti surfaces.     

Characterization of a Streptococcus sp.-Veillonella sp. community micromanipulated from dental plaque

Streptococci and veillonellae occur in mixed-species colonies during formation of early dental plaque. One factor hypothesized to be important in assembly of these initial communities is coaggregation (cell-cell recognition by genetically distinct bacteria). Intrageneric coaggregation of streptococci occurs when a lectin-like adhesin on one streptococcal species recognizes a receptor polysaccharide (RPS) on the partner species. Veillonellae also coaggregate with streptococci. These genera interact metabolically; lactic acid produced by streptococci is a carbon source for veillonellae. To transpose these interactions from undisturbed dental plaque to an experimentally tractable in vitro biofilm model, a community consisting of RPS-bearing streptococci juxtaposed with veillonellae was targeted by quantum dot-based immunofluorescence and then micromanipulated off the enamel surface and cultured. Besides the expected antibody-reactive cell types, a non-antibody-reactive streptococcus invisible during micromanipulation was obtained. The streptococci were identified as Streptococcus oralis (RPS bearing) and Streptococcus gordonii (adhesin bearing). The veillonellae could not be cultivated; however, a veillonella 16S rRNA gene sequence was amplified from the original isolation mixture, and this sequence was identical to the sequence of the previously studied organism Veillonella sp. strain PK1910, an oral isolate in our culture collection. S. oralis coaggregated with S. gordonii by an RPS-dependent mechanism, and both streptococci coaggregated with PK1910, which was used as a surrogate during in vitro community reconstruction. The streptococci and strain PK1910 formed interdigitated three-species clusters when grown as a biofilm using saliva as the nutritional source. PK1910 grew only when streptococci were present. This study confirms that RPS-mediated intrageneric coaggregation occurs in the earliest stages of plaque formation by bringing bacteria together to create a functional community.     

Rational design of bifunctional chimeric peptides that combine antimicrobial and titanium binding activity

Bacterial biofilm formation remains a serious problem for clinical materials and often leads to implant failure. To counteract bacterial adhesion, which initiates biofilm formation, the development of antibiotic surface coating strategies is of high demand and warrants further investigations. In this study, we have created bifunctional chimeric peptides by fusing the recently developed antimicrobial peptide MGD2 (GLRKRLRKFFNKIKF) with different titanium-binding sequences. The novel peptides were investigated regarding their antibacterial potential against a set of different bacterial strains including drug-resistant Staphylococcus aureus. All peptides showed high antimicrobial activities both when in solution and when immobilized on titanium surfaces. Owing to the ease of synthesis and handling, the herein described peptides might be a true alternative to prevent bacterial biofilm formation.     

The synthetic human beta-defensin-3 C15 peptide exhibits antimicrobial activity against <Emphasis Type="Italic">Streptococcus mutans</Emphasis>, both alone and in combination with dental disinfectants

Streptococcus mutans is a major etiologic agent of human dental caries that forms biofilms on hard tissues in the human oral cavity, such as tooth and dentinal surfaces. Human β-defensin-3 (HBD3) is a 45-amino-acid natural antimicrobial peptide that has broad spectrum antimicrobial activity against bacteria and fungi. A synthetic peptide consisting of the C-terminal 15 amino acids of HBD3 (HBD3-C15) was recently shown to be sufficient for its antimicrobial activity. Thus, clinical applications of this peptide have garnered attention. In this study, we investigated whether HBD3-C15 inhibits the growth of the representative cariogenic pathogen Streptococcus mutans and its biofilm formation. HBD3-C15 inhibited bacterial growth, exhibited bactericidal activity, and attenuated bacterial biofilm formation in a dose-dependent manner. HBD3-C15 potentiated the bactericidal and anti-biofilm activity of calcium hydroxide (CH) and chlorhexidine digluconate (CHX), which are representative disinfectants used in dental clinics, against S. mutans. Moreover, HBD3-C15 showed antimicrobial activity by inhibiting biofilm formation by S. mutans and other dentinophilic bacteria such as Enterococcus faecalis and Streptococcus gordonii, which are associated with dental caries and endodontic infection, on human dentin slices. These effects were observed for HBD3-C15 alone and for HBD3-C15 in combination with CH or CHX. Therefore, we suggest that HBD3-C15 is a potential alternative or additive disinfectant that can be used for the treatment of oral infectious diseases, including dental caries and endodontic infections.     

LuxS-Based Signaling Affects Streptococcus mutans Biofilm Formation

Streptococcus mutans is implicated as a major etiological agent in human dental caries, and one of the important virulence properties of this organism is its ability to form biofilms (dental plaque) on tooth surfaces. We examined the role of autoinducer-2 (AI-2) on S. mutans biofilm formation by constructing a GS-5 luxS-null mutant. Biofilm formation by the luxS mutant in 0.5% sucrose defined medium was found to be markedly attenuated compared to the wild type. Scanning electron microscopy also revealed that biofilms of the luxS mutant formed larger clumps in sucrose medium compared to the parental strain. Therefore, the expression of glucosyltransferase genes was examined and the gtfB and gtfC genes, but not the gtfD gene, in the luxS mutant were upregulated in the mid-log growth phase. Furthermore, we developed a novel two-compartment system to monitor AI-2 production by oral streptococci and periodontopathic bacteria. The biofilm defect of the luxS mutant was complemented by strains of S. gordonii, S. sobrinus, and S. anginosus; however, it was not complemented by S. oralis, S. salivarius, or S. sanguinis. Biofilm formation by the luxS mutant was also complemented by Porphyromonas gingivalis 381 and Actinobacillus actinomycetemcomitans Y4 but not by a P. gingivalis luxS mutant. These results suggest that the regulation of the glucosyltransferase genes required for sucrose-dependent biofilm formation is regulated by AI-2. Furthermore, these results provide further confirmation of previous proposals that quorum sensing via AI-2 may play a significant role in oral biofilm formation.     

Crystalline anatase-rich titanium can reduce adherence of oral streptococci

Dental implant abutments that emerge through the mucosa are rapidly covered with a salivary protein pellicle to which bacteria bind, initiating biofilm formation. In this study, adherence of early colonizing streptococci, Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis and Streptococcus sanguinis to two saliva-coated anodically oxidized surfaces was compared with that on commercially pure titanium (CpTi). Near edge X-ray absorption (NEXAFS) showed crystalline anatase was more pronounced on the anodically oxidized surfaces than on the CpTi. As revealed by fluorescence microscopy, a four-species mixture, as well as individual bacterial species, exhibited lower adherence after 2?h to the saliva-coated, anatase-rich surfaces than to CpTi. Since wettability did not differ between the saliva-coated surfaces, differences in the concentration and/or configuration of salivary proteins on the anatase-rich surfaces may explain the reduced bacterial binding effect. Anatase-rich surfaces could thus contribute to reduced overall biofilm formation on dental implant abutments through diminished adherence of early colonizers.     

Reduced Glutathione Mediates Resistance to H2S Toxicity in Oral Streptococci

Periodontal disease is associated with changes in the composition of the oral microflora, where health-associated oral streptococci decrease while Gram-negative anaerobes predominate in disease. A key feature of periodontal disease-associated anaerobes is their ability to produce hydrogen sulfide (H₂S) abundantly as a by-product of anaerobic metabolism. So far, H₂S has been reported to be either cytoprotective or cytotoxic by modulating bacterial antioxidant defense systems. Although oral anaerobes produce large amounts of H₂S, the potential effects of H₂S on oral streptococci are currently unknown. The aim of this study was to determine the effects of H₂S on the survival and biofilm formation of oral streptococci. The growth and biofilm formation of Streptococcus mitis and Streptococcus oralis were inhibited by H₂S. However, H₂S did not significantly affect the growth of Streptococcus gordonii or Streptococcus sanguinis. The differential susceptibility of oral streptococci to H₂S was attributed to differences in the intracellular concentrations of reduced glutathione (GSH). In the absence of GSH, H₂S elicited its toxicity through an iron-dependent mechanism. Collectively, our results showed that H₂S exerts antimicrobial effects on certain oral streptococci, potentially contributing to the decrease in health-associated plaque microflora.     

Tissue Plasminogen Activator Coating on Implant Surfaces Reduces Staphylococcus aureus Biofilm Formation

Staphylococcus aureus biofilm infections of indwelling medical devices are a major medical challenge because of their high prevalence and antibiotic resistance. As fibrin plays an important role in S. aureus biofilm formation, we hypothesize that coating of the implant surface with fibrinolytic agents can be used as a new method of antibiofilm prophylaxis. The effect of tissue plasminogen activator (tPA) coating on S. aureus biofilm formation was tested with in vitro microplate biofilm assays and an in vivo mouse model of biofilm infection. tPA coating efficiently inhibited biofilm formation by various S. aureus strains. The effect was dependent on plasminogen activation by tPA, leading to subsequent local fibrin cleavage. A tPA coating on implant surfaces prevented both early adhesion and later biomass accumulation. Furthermore, tPA coating increased the susceptibility of biofilm infections to antibiotics. In vivo, significantly fewer bacteria were detected on the surfaces of implants coated with tPA than on control implants from mice treated with cloxacillin. Fibrinolytic coatings (e.g., with tPA) reduce S. aureus biofilm formation both in vitro and in vivo, suggesting a novel way to prevent bacterial biofilm infections of indwelling medical devices.     

Effects of antimicrobial peptide L-K6, a temporin-1CEb analog on oral pathogen growth,Streptococcus mutans biofilm formation,and anti-inflammatory activity

Dental caries and periodontitis are common bacterial mouth infections. As a potentially attractive substitute for conventional antibiotics, antimicrobial peptides have been widely tested and used for controlling bacterial infections. In this study, we tested the efficacy of the peptides from the skin secretions of Rana chensinensis for killing several major cariogenic and periodontic pathogens as well as Candida albicans. L-K6, a temporin-1CEb analog, exhibited high antimicrobial activity against the tested oral pathogens and was able to inhibit Streptococcus mutans biofilm formation and reduce 1-day-old S. mutans biofilms with a minimum biofilm inhibitory concentration and reducing concentration of 3.13 and 6.25 μM, respectively. The results of confocal laser scanning microscopy demonstrated that the peptide significantly reduced cell viability within oral biofilms. Furthermore, as little as 5 μM L-K6 significantly inhibited lipopolysaccharide (LPS)- and interleukin-1β-induced productions of interleukin-8 and tumor necrosis factor-α from THP-1 monocytic cells. This anti-inflammatory activity is associated with the binding of L-K6 to LPS and neutralizing LPS-induced proinflammatory responses in THP-1 cells, as well as dissociating LPS aggregates. Our results suggest that L-K6 may have potential clinical applications in treating dental caries by killing S. mutans within dental plaque and acting as anti-inflammatory agents in infected tissues.     

Antimicrobial effects of herbal extracts on Streptococcus mutans and normal oral streptococci

Streptococcus mutans is associated with dental caries. A cariogenic biofilm, in particular, has been studied extensively for its role in the formation of dental caries. Herbal extracts such as Cudrania tricuspidata, Sophora flavescens, Ginkgo biloba, and Betula Schmidtii have been used as a folk remedy for treating diseases. The purpose of this study was to evaluate and compare the antibacterial activity of herbal extracts against normal oral streptococci, planktonic and biofilm of S. mutans. Streptococcus gordonii, Streptococcus oralis, Streptococcus salivarius, Streptococcus sanguinis, and S. mutans were cultivated with brain heart infusion broth and susceptibility assay for the herbal extracts was performed according to the protocol of Clinical and Laboratory Standard Institute. Also, S. mutans biofilm was formed on a polystyrene 12-well plate and 8-well chamber glass slip using BHI broth containing 2% sucrose and 1% mannose after conditioning the plate and the glass slip with unstimulated saliva. The biofilm was treated with the herbal extracts in various concentrations and inoculated on Mitis-Salivarius bacitracin agar plate for enumeration of viable S. mutans by counting colony forming units. Planktonic S. mutans showed susceptibility to all of the extracts and S. mutans biofilm exhibited the highest level of sensitivity for the extracts of S. flavescens. The normal oral streptococci exhibited a weak susceptibility in comparison to S. mutans. S. oralis, however, was resistant to all of the extracts. In conclusion, the extract of S. flavescens may be a potential candidate for prevention and management of dental caries.     

口腔种植材料表面特性与生物膜形成研究进展

人类口腔环境为微生物提供了适宜生存的条件,多种微生物在牙齿表面形成了由基质包裹相互粘附的口腔生物膜,口腔生物膜是口腔微生物生存、代谢和致病的基础。随着1965年Brnemark种植体在临床上的成功应用,种植相关材料周围致病菌导致的种植体周围炎成为种植修复最常见的并发症之一,影响种植修复的远期效果。种植体周围炎引起了许多关注,并且口腔种植材料表面的特性和口腔生物膜的形成密切相关。本文就种植材料及天然牙齿表面的生物膜形成、种植材料表面特性对口腔生物膜及细菌粘附的影响因素、增强种植材料抗菌性能的方法以及未来的研究方向等作一综述。     

Plausible Drug Targets in the Streptococcus mutans Quorum Sensing Pathways to Combat Dental Biofilms and Associated Risks

Streptococcus mutans, a Gram positive facultative anaerobe, is one among the approximately seven hundred bacterial species to exist in human buccal cavity and cause dental caries. Quorum sensing (QS) is a cell-density dependent communication process that respond to the inter/intra-species signals and elicit responses to show behavioral changes in the bacteria to an aggressive forms. In accordance to this phenomenon, the S. mutans also harbors a Competing Stimulating Peptide (CSP)-mediated quorum sensing, ComCDE (Two-component regulatory system) to regulate several virulence-associated traits that includes the formation of the oral biofilm (dental plaque), genetic competence and acidogenicity. The QS-mediated response of S. mutans adherence on tooth surface (dental plaque) imparts antibiotic resistance to the bacterium and further progresses to lead a chronic state, known as periodontitis. In recent years, the oral streptococci, S. mutans are not only recognized for its cariogenic potential but also well known to worsen the infective endocarditis due to its inherent ability to colonize and form biofilm on heart valves. The review significantly appreciate the increasing complexity of the CSP-mediated quorum-sensing pathway with a special emphasis to identify the plausible drug targets within the system for the development of anti-quorum drugs to control biofilm formation and associated risks.     

Biomaterials for orthopedics: anti-biofilm activity of a new bioactive glass coating on titanium implants

Abstract

This study evaluated adhesion and biofilm formation by Candida albicans, Pseudomonas aeruginosa and Staphylococcus epidermidis on surfaces of titanium (Ti) and titanium coated with F18 Bioactive Glass (BGF18). Biofilms were grown and the areas coated with biofilm were determined after 2, 4 and 8?h. Microscopy techniques were applied in order to visualize the structure of the mature biofilm and the extracellular matrix. On the BGF18 specimens, there was less biofilm formation by C. albicans and S. epidermidis after incubation for 8?h. For P. aeruginosa biofilm, a reduction was observed after incubation for 4?h, and it remained reduced after 8?h on BGF18 specimens. All biofilm matrices seemed to be thicker on BGF18 surface than on titanium surfaces. BGF18 showed significant anti-biofilm activity in comparison with Ti in the initial periods of biofilm formation; however, there was extensive biofilm after incubation for 48?h.     

Effect of biofouling on anodized and sol-gel treated titanium surfaces: a comparative study

Anodization and sol-gel treatments of titanium (Ti) were evaluated as biofilm control measures on surfaces exposed to seawater exposed to ultraviolet light. Anodized and sol-gel treated specimens were characterized using Raman spectroscopy to confirm the presence of TiO₂. The single anatase phase was observed at the anodized surfaces whereas the anatase/rutile mixed phase was detected on the sol-gel coated surfaces. After exposure of the specimens to seawater, biofilms were characterized by total viable counts, and epifluorescence and Raman microscopy. These techniques confirmed the reduction in biofilm formation on both the anodized and sol-gel coated Ti specimens compared to the untreated specimens. Biofilm control by anodization was found to be more effective than by sol-gel treatment of the specimens. The higher particle size and the inhomogeneity at the sol-gel coated surfaces produced less effective biofilm control.     

Destruction of oral biofilms formed in situ on machined titanium (Ti) surfaces by cold atmospheric plasma

The decontamination of implant surfaces represents the basic procedure in the management of peri-implant diseases, but it is still a challenge. The study aimed to evaluate the degradation of oral biofilms grown in situ on machined titanium (Ti) discs by cold atmospheric plasma (CAP). ～ 200 Ti discs were exposed to the oral cavities of five healthy human volunteers for 72?h. The resulting biofilms were divided randomly between the following treatments: CAP (which varied in mean power, treatment duration, and/or the gas mixture), and untreated and treated controls (diode laser, air-abrasion, chlorhexidine). The viability, quantity, and morphology of the biofilms were determined by live/dead staining, inoculation onto blood agar, quantification of the total protein content, and scanning electron microscopy. Exposure to CAP significantly reduced the viability and quantity of biofilms compared with the positive control treatments. The efficacy of treatment with CAP correlated with the treatment duration and plasma power. No single method achieved complete biofilm removal; however, CAP may provide an effective support to established decontamination techniques for treatment of peri-implant diseases.     

Streptococcus gordonii biofilm formation: identification of genes that code for biofilm phenotypes

Viridans streptococci, which include Streptococcus gordonii, are pioneer oral bacteria that initiate dental plaque formation. Sessile bacteria in a biofilm exhibit a mode of growth that is distinct from that of planktonic bacteria. Biofilm formation of S. gordonii Challis was characterized using an in vitro biofilm formation assay on polystyrene surfaces. The same assay was used as a nonbiased method to screen isogenic mutants generated by Tn916 transposon mutagenesis for defective biofilm formation. Biofilms formed optimally when bacteria were grown in a minimal medium under anaerobic conditions. Biofilm formation was affected by changes in pH, osmolarity, and carbohydrate content of the growth media. Eighteen biofilm-defective mutants of S. gordonii Challis were identified based on Southern hybridization with a Tn916-based probe and DNA sequences of the Tn916-flanking regions. Molecular analyses of these mutants showed that some of the genes required for biofilm formation are involved in signal transduction, peptidoglycan biosynthesis, and adhesion. These characteristics are associated with quorum sensing, osmoadaptation, and adhesion functions in oral streptococci. Only nine of the biofilm-defective mutants had defects in genes of known function, suggesting that novel aspects of bacterial physiology may play a part in biofilm formation. Further identification and characterization of biofilm-associated genes will provide insight into the molecular mechanisms of biofilm formation of oral streptococci.     

Sulfated vizantin inhibits biofilm maturation by Streptococcus mutans

Streptococcus mutans is the main pathogen of dental caries and adheres to the tooth surface via soluble and insoluble glucans produced by the bacterial glucosyltransferase enzyme. Thus, the S. mutans glucosyltransferase is an important virulence factor for this cariogenic bacterium. Sulfated vizantin effectively inhibits biofilm formation by S. mutans without affecting its growth. In this study, less S. mutans biofilm formation occurred on hydroxyapatite discs coated with sulfated vizantin than on noncoated discs. Sulfated vizantin showed no cytotoxicity against the human gingival cell line Ca9-22. Sulfated vizantin dose-dependently inhibited the extracellular release of cell-free glucosyltransferase from S. mutans and enhanced the accumulation of cell-associated glucosyltransferase, compared with that observed with untreated bacteria. Sulfated vizantin disrupted the localization balance between cell-associated glucosyltransferase and cell-free glucosyltransferase, resulting in inhibited biofilm maturation. These results indicate that sulfated vizantin can potentially serve as a novel agent for preventing dental caries.     

Antimicrobial Peptides and their Potential as Oral Therapeutic Agents

Dental caries (tooth decay) and periodontal diseases are the most prevalent bacterial infectious diseases of mankind, together affecting almost the entire population of the world. Both diseases are caused by oral bacteria that exist as components of a polymicrobial biofilm, known as dental plaque, on the tooth surface. The control of specific types of bacteria and/or total numbers of bacteria in dental plaque could lead to prevention or resolution of disease. Antimicrobial peptides isolated from a wide range of natural sources have been known for over 30 years yet little progress had been made in the therapeutic application of these peptides. This is due in part to the characteristics, including susceptibility to proteolysis, of the cationic amphipathic antimicrobial peptides that form the majority of peptides discovered to date. Bovine milk is a readily available source of a range of bioactive peptides. We have isolated and characterized a novel anionic antimicrobial peptide, Kappacin, from bovine milk. Antibacterial activity of the peptide is increased when it is complexed with zinc ions. We have demonstrated that a Kappacin:Zn²⁺ preparation is able to suppress the growth of oral cariogenic bacteria in a biofilm. The Kappacin:Zn²⁺ antibacterial complex may have potential as an additive to oral care products and other delivery vehicles for the control of oral disease.