Targeted Antimicrobial Therapy Against Streptococcus mutans Establishes Protective Non-cariogenic Oral Biofilms and Reduces Subsequent Infection

Aim Dental biofilms are complex communities composed largely of harmless bacteria. Certain pathogenic species including Streptococcus mutans （S. mutans） can become predominant when host factors such as dietary sucrose intake imbalance the biofilm ecology. Current approaches to control S. mutans infection are not pathogen-specific and eliminate the entire oral community along with any protective benefits provided. Here, we tested the hypothesis that removal of S. mutans from the oral community through targeted antimicrobial therapy achieves protection against subsequent S. mutans colonization. Methodology Controlled amounts of S. mutans were mixed with S. mutans-free saliva, grown into biofilms and visualized by antibody staining and cfu quantization. Two specifically-targeted antimicrobial peptides （STAMPs） against S. mutans were tested for their ability to reduce S. mutans biofilm incorporation upon treatment of the inocula. The resulting biofilms were also evaluated for their ability to resist subsequent exogenous S. mutans colonization. Results S. mutans colonization was considerably reduced （9 ± 0.4 fold reduction, P=0.01） when the surface was preoccupied with saliva-derived biofilms. Furthermore, treatment with S. mutans-specific STAMPs yielded S. mutans-deficient biofilms with significant protection against further S. mutans colonization （5 minutes treatment： 38 ± 13 fold reduction P=0.01; 16 hours treatment： 96 ± 28 fold reduction P=0.07）. Conclusion S. mutans infection is reduced by the pre- sence of existing biofilms. Thus maintaining a healthy or ＂normal＂ biofilm through targeted antimicrobial therapy （such as the STAMPs） could represent an effective strategy for the treatment and prevention of S. mutans colonization in the oral cavity and caries progression.

Effect of antibacterial photodynamic therapy on Streptococcus mutans plaque biofilm in vitro

The main objective of this study is to evaluate the antibacterial effect of antibacterial pho-todynamic therapy(aPDT)on Streptococcus mutans(S.mutans)biofilm model in vitro.The selection of photosensitizers is the key step for the efficacy of photodynamic therapy(PDT).However,no studies have been conducted in the oral field to compare the functional char-acteristics and application effects of PDT mediated by various photosensitizers.In this re-search,the antibacterial effect of Methylene blue(MB)/650 nm laser and Hematoporphyrin monomethyl ether(HMME)/532 nm laser on S.mutans biofilm was compared under different energy densities to provide experimental reference for the clinical application of the two PDT.The yield of lactic acid was analyzed by Colony forming unit(CFU)and spectrophotometry,and the complete biofilm activity was measured by Confocal Laser Scanning Microscopy(CLSM)to evaluate the bactericidal effect on each group.Based on the results of CFU,the bacterial colonies formed by 30.4J/cm^(2)532nm MB-aPDT group and 30.4J/cm^(2)532nm HMME-aPDT group were significantly less than those in other groups,and the bacterial colonies in HMME-aPDT group were less than those in HMME-aPDT group.Lactic acid production in all treatment groups except the photosensitizer group was statistically lower than that in the normal saline control group.The activity of bacterial plaque biofilm was significantly decreased in the two groups treated with 30.4 J/cm^(2) aPDT.Therefore,aPDT suitable for energy measurement can kill S.mutans plaque biofilm,and MB-aPDT is better than HMME-aPDT.

Development and evaluation of a safe and effective sugar-free herbal lollipop that kills cavity-causing bacteria

Dental caries （tooth decay） is caused by a specific group of cariogenic bacteria, like Streptococcus mutans, which convert dietary sugars into acids that dissolve the mineraI in tooth structure. Killing cariogenic bacteria is an effective way to control or prevent tooth decay. In a previous study, we discovered a novel compound （Glycyrrhizol A）, from the extraction of licorice roots, with strong antimicrobial activity against cariogenic bacteria. In the current study, we developed a method to produce these specific herbal extracts in large quantities, and then used these extracts to develop a sugar-free lollipop that effectively kills cariogenic bacteria like Streptococcus mutans. Further studies showed that these sugar-free lollipops are safe and their antimicrobial activity is stable. Two pilot human studies indicate that a brief application of these lollipops （twice a day for ten days） led to a marked reduction of cariogenic bacteria in oral cavity among most human subjects tested. This herbal lollipop could be a novel tool to promote oral health through functional foods.

Importance of Pharmacotherapeutic Follow-Up in Odontopediatrics

The most common cause of admission to the Pediatric Dentistry service is dental pain, active deafness and an oppressive sensation that is sometimes throbbing and burning. Pharmacotherapy in Pediatric Dentistry must be effective, safe, and rational in neonates, infants, and children. The pharmacotherapeutic follow-up of pediatric patients from Integral Clinic of the Odontopediatric Specialty (CLIO) and Kindergarten Clinic (CLIJANI), Autonomous University of Zacatecas (UAZ) was carried out. Through an observational, exploratory, and cross-sectional study, 23 patients from the Pediatric Dentistry Specialty Clinic (CLIO/UAO/UAZ) and 35 clinical records of patients from CLIJANI, from August 2019-2020, were analyzed. Prior authorization for the patient, an interview, and pharmacotherapeutic follow-up were performed, recording data on the indicated drug, the dose, and the schedule of use. On carrying out the interview on pharmacotherapy with the parents or guardians who accompany the patient, 91.3% of the pediatric patients were not administered pharmacological treatment. It was observed that there is no adequate adherence to the pharmacological treatment in pediatric patients.

Effect of Photoactivated Hypericin on Growth and Antibiotic Susceptibility of Hospital-Related Staphylococcus aureus and Enterococcus sp. Clinical Strains

Resistance against commonly used antibiotics is a serious clinical problem in recent medical practice. There exist several bacterial strains in which the possibilities of their inhibition are very limited due to multidrug resistance. Antimicrobial photodynamic therapy (aPDT) represents an option how to effectively suppress the growth of resistant pathogens. In this work we have studied interactions of potent photosensitizer hypericin (Hyp) with hospital-related gram positive (Gram+) and gram negative (Gram-) bacterial strains and the effects of photodynamic activated Hyp on bacterial susceptibility and/or resistance of these strains to antibiotics. We demonstrated a significant influence of photoactivated Hyp on growth of Staphylococcus aureus and Enterococcus sp. We have also shown that it is extremely important to use the effective concentrations of Hyp for aPDT, which completely inhibit the growth of microorganisms. Otherwise, there appears an increase in resistance, probably due to the activation of efflux mechanisms, which are involved in the efflux of Hyp and antibiotics as well.

Bioresponsive nanotherapy for preventing dental caries by inhibiting multispecies cariogenic biofilms

Early childhood caries(ECC)is a public healthcare concern that greatly reduces the quality of life of young children.As a leading factor of ECC,cariogenic biofilms are composed of acidogenic/aciduric pathogens and extracellular polysaccharides(EPSs),creating an acidic and protected microenvironment.Antimicrobial photodynamic therapy(aPDT)is a noninvasive,painless,and efficient therapeutic approach that is suitable for treating ECC.However,due to the hyperfine structure of cariogenic biofilms,most photosensitizers(PSs)could not access and penetrate deeply in biofilms,which dramatically hamper their efficiency in the clinic.Herein,bioresponsive nanoparticle loaded with chlorin e6(MPP-Ce6)is developed,which largely increases the penetration depth(by over 75%)and retention(by over 100%)of PS in the biofilm compared with free Ce6.Furthermore,MPP-Ce6-mediated aPDT not only kills the bacteria in preformed biofilms but also inhibits multispecies biofilm formation.A rampant caries model is established to mimic ECC in vivo,where the population of cariogenic bacteria is decreased to 10%after MPP-Ce6-mediated aPDT.Importantly,the number and severity of carious lesions are efficiently reduced via Keyes’scoring and micro-CT analysis.This simple but effective strategy can serve as a promising approach for daily oral hygiene in preventing ECC.

Electrospun nanofibrous membranes meet antibacterial nanomaterials:From preparation strategies to biomedical applications

Electrospun nanofibrous membranes(eNFMs)have been extensively developed for bio-applications due to their structural and compositional similarity to the natural extracellular matrix.However,the emergence of antibiotic resistance in bacterial infections significantly impedes the further development and applications of eNFMs.The development of antibacterial nanomaterials substantially nourishes the engineering design of antibacterial eNFMs for combating bacterial infections without relying on antibiotics.Herein,a comprehensive review of diverse fabrication techniques for incorporating antibacterial nanomaterials into eNFMs is presented,encompassing an exhaustive introduction to various nanomaterials and their bactericidal mechanisms.Furthermore,the latest achievements and breakthroughs in the application of these antibacterial eNFMs in tissue regenerative therapy,mainly focusing on skin,bone,periodontal and tendon tissues regeneration and repair,are systematically summarized and discussed.In particular,for the treatment of skin infection wounds,we highlight the antibiotic-free antibacterial therapy strategies of antibacterial eNFMs,including(i)single model therapies such as metal ion therapy,chemodynamic therapy,photothermal therapy,and photodynamic therapy;and(ii)multimodel therapies involving arbitrary combinations of these single models.Additionally,the limitations,challenges and future opportunities of antibacterial eNFMs in biomedical applications are also discussed.We anticipate that this comprehensive review will provide novel insights for the design and utilization of antibacterial eNFMs in future research.

Identification of a phage-derived depolymerase specific for KL47 capsule of Klebsiella pneumoniae and its therapeutic potential in mice

Klebsiella pneumoniae is one of the major pathogens causing global multidrug-resistant infections.Therefore,strategies for preventing and controlling the infections are urgently needed.Phage depolymerase,often found in the tail fiber protein or the tail spike protein,is reported to have antibiofilm activity.In this study,phage P560isolated from sewage showed specific for capsule locus type KL47 K.pneumoniae,and the enlarged haloes around plaques indicated that P560 encoded a depolymerase.The capsule depolymerase,ORF43,named P560dep,derived from phage P560 was expressed,purified,characterized and evaluated for enzymatic activity as well as specificity.We reported that the capsule depolymerase P560dep,can digest the capsule polysaccharides on the surface of KL47 type K.pneumoniae,and the depolymerization spectrum of P560dep matched to the host range of phage P560,KL47 K.pneumoniae.Crystal violet staining assay showed that P560dep was able to significantly inhibit biofilm formation.Further,a single dose(50μg/mouse)of depolymerase intraperitoneal injection protected 90%–100%of mice from lethal challenge before or after infection by KL47 carbapenem-resistant K.pneumoniae.And pathological changes were alleviated in lung and liver of mice infected by KL47 type K.pneumoniae.It is demonstrated that depolymerase P560dep as an attractive antivirulence agent represents a promising tool for antimicrobial therapy.

Photo-catalytic Staphylococcus aureus inactivation and biofilm destruction with novel bis-tridentate iridium(Ⅲ) photocatalyst

Bacterial infection is currently a serious challenge globally, causing death of thousands of human beings. New antimicrobial agents with novel mechanism of action are urgently needed. Transition metal complexes have shown great potentials in photodynamic and photocatalytic therapy. Herein, we take full advantage of metal photocatalyst and successfully developed a novel cyclometalated iridium(Ⅲ) complex(Ir1) with higher biofilm damage efficiency than the clinical antibiotics. Ir1 synergistically generates reactive oxygen species and coenzyme photocatalytic activity with high efficiency under white light irradiation. Combined with these properties, Ir1 exhibited excellent photoinactivation of S. aureus and effectively damaged the biofilm. This work provides a new approach for the development of antibacterial photodynamic therapy.