Antibacterial and Antibiofilm Activity of Temporin-GHc and Temporin-GHd Against Cariogenic Bacteria, Streptococcus mutans

Antibiofilm Analysis, Synergistic Potential and Biocompatibility Evaluation of a Bacteriocin from Bacillus subtilis (MK733983)

This study emphasizes the potency of a bacteriocin screened from Bacillus subtilis (MK733983) of ethnomedicinal origin. Antibiofilm analysis with 0.5-3x minimal bacteriocin concentrations with critical and highly prioritized standard microbes such as Staphylococcus aureus, Mycobacterium smegmatis, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Chromobacterium violecium showed potential biofilm inhibition and eradication of ≥ 5-99%, ≥ 1-86% respectively that correlated with biofilm viable cell-count. The bacteriocin exhibited remarkable synergistic potential with antibiotics like Amikacin, Ampicillin, Bacitracin, Chloramphenicol, Kanamycin, Norfloxacin, Vancomycin, Tetracycline, and Streptomycin. The sum of the fractional inhibitory concentrations was less than 0.5, which corresponded to the preliminary evaluation that included disc diffusion assays and checkerboard assays. In addition to synergism, the time-kill assays revealed a 2 or 3 log10 (1000-fold) reduction, indicating bactericidal potential. Bacteriocin's effect on the growth dynamics of microorganisms has revealed its ability to intervene early and reduce microbial multiplication within 15 h of administration. Observations with a scanning electron microscope validated the antibiofilm capability. Methyl thiazol tetrazolium assay on 3T3 (normal fibroblast cell lines) up to 100 μg/ml of bacteriocin for 96 h (24 h-interval) revealed that the bacteriocin is not cytotoxic. It was also confirmed by trypan blue staining of the 3T3 cells at 96 h. Many biofilm-forming bacteria are known for causing harmful infections and resistance, and there is a growing need for new treatments. Bacteriocins are potential antibiotic alternatives, and the findings of this study are capable of being examined for larger application prospects.

Current approaches to produce durable biomaterials: Trends in polymeric materials for restorative dentistry applications

Dental caries continues to be a public health issue, especially more evident in underserved populations throughout the U.S. Unfortunately, especially with an aging population, hundreds of thousands of resin composite restorations are replaced each year due to recurring decay and fracture. According to several cohort studies, the average life span of this type of restoration is 10 years or less, depending on the caries risk level of the patient and the complexity of the restorative procedure. Any new material development must depart from the simple restoration of form paradigm, in which the filling is simply inert/biocompatible. This review will discuss novel antibiofilm structures, based on a targeted approach specifically against dysbiotic bacteria. Biofilm coalescence can be prevented by using glycosyl transferase - GTF inhibitors, in a non-bactericidal approach. On the tooth substrate side, MMP-inhibiting molecules can improve the stability of the collagen in the hybrid layer. This review will also discuss the importance of testing the materials in a physiologically relevant environment, mimicking the conditions in the mouth in terms of mechanical loading, bacterial challenge, and the presence of saliva. Ultimately, the goal of materials development is to achieve durable restorations, capable of adapting to the oral environment and resisting challenges that go beyond mechanical demands. That way, we can prevent the unnecessary loss of additional tooth structure that comes with every re-treatment. CLINICAL SIGNIFICANCE: While proper restorative technique and patient education in terms of diet and oral hygiene are crucial factors in increasing the longevity of esthetic direct restorations, materials better able to resist and interact with the conditions of the oral environment are still needed. Reproducing the success of dental amalgams with esthetic materials continues to be the Holy Grail of materials development.

Intestinal biofilms: pathophysiological relevance, host defense, and therapeutic opportunities

SUMMARYThe human intestinal tract harbors a profound variety of microorganisms that live in symbiosis with the host and each other. It is a complex and highly dynamic environment whose homeostasis directly relates to human health. Dysbiosis of the gut microbiota and polymicrobial biofilms have been associated with gastrointestinal diseases, including irritable bowel syndrome, inflammatory bowel diseases, and colorectal cancers. This review covers the molecular composition and organization of intestinal biofilms, mechanistic aspects of biofilm signaling networks for bacterial communication and behavior, and synergistic effects in polymicrobial biofilms. It further describes the clinical relevance and diseases associated with gut biofilms, the role of biofilms in antimicrobial resistance, and the intestinal host defense system and therapeutic strategies counteracting biofilms. Taken together, this review summarizes the latest knowledge and research on intestinal biofilms and their role in gut disorders and provides directions toward the development of biofilm-specific treatments.

Synthesis and evaluation of di-heterocyclic benzazole compounds as potential antibacterial and anti-biofilm agents against Staphylococcus aureus

Cumulative escalation in antibiotic-resistant pathogens necessitates the quest for novel antimicrobial agents, as current options continue to diminish bacterial resistance. Herein, we report the synthesis of di-heterocyclic benzazole structures (12-19) and their in vitro evaluation for some biological activities. Compounds 16 and 17 demonstrated potent antibacterial activity (MIC = 7.81 μg/mL) against Staphylococcus aureus, along with significant anti-biofilm activity. Noteworthy is the capability of Compound 17 to inhibit biofilm formation by at least 50% at sub-MIC (3.90 μg/mL) concentration. Furthermore, both compounds exhibited the potential to inhibit preformed biofilm by at least 50% at the MIC concentration (7.81 μg/mL). Additionally, Compounds 16 and 17 were examined for cytotoxic effects in HFF-1 cells, using the MTT method, and screened for binding interactions within the active site of S. aureus DNA gyrase using in silico molecular docking technique, employing AutoDock 4.2.6 and Schrödinger Glidse programs. Overall, our findings highlight Compounds 16 and 17 as promising scaffolds warranting further optimization for the development of effective antibacterial and anti-biofilm agents.

Dual-function antimicrobial-antibiofilm peptide hybrid to tackle biofilm-forming Staphylococcus epidermidis

BACKGROUND

Due to their resistance and difficulty in treatment, biofilm-associated infections are problematic among hospitalized patients globally and account for 60% of all bacterial infections in humans. Antibiofilm peptides have recently emerged as an alternative treatment since they can be effectively designed and exert a different mode of biofilm inhibition and eradication.

METHODS

A novel antibiofilm peptide, BiF, was designed from the conserved sequence of 18 α-helical antibiofilm peptides by template-assisted technique and its activity was improved by hybridization with a lipid binding motif (KILRR). Novel antibiofilm peptide derivatives were modified by substituting hydrophobic amino acids at positions 5 or 7, and both, with positively charged lysines (L5K, L7K). These peptide derivatives were tested for antibiofilm and antimicrobial activities against biofilm-forming Staphylococcus epidermidis and multiple other microbes using crystal violet and broth microdilution assays, respectively. To assess their impact on mammalian cells, the toxicity of peptides was determined through hemolysis and cytotoxicity assays. The stability of candidate peptide, BiF2_5K7K, was assessed in human serum and its secondary structure in bacterial membrane-like environments was analyzed using circular dichroism. The action of BiF2_5K7K on planktonic S. epidermidis and its effect on biofilm cell viability were assessed via viable counting assays. Its biofilm inhibition mechanism was investigated through confocal laser scanning microscopy and transcription analysis. Additionally, its ability to eradicate mature biofilms was examined using colony counting. Finally, a preliminary evaluation involved coating a catheter with BiF2_5K7K to assess its preventive efficacy against S. epidermidis biofilm formation on the catheter and its surrounding area.

RESULTS

BiF2_5K7K, the modified antibiofilm peptide, exhibited dose-dependent antibiofilm activity against S. epidermidis. It inhibited biofilm formation at subinhibitory concentrations by altering S. epidermidis extracellular polysaccharide production and quorum-sensing gene expression. Additionally, it exhibited broad-spectrum antimicrobial activity and no significant hemolysis or toxicity against mammalian cell lines was observed. Its activity is retained when exposed to human serum. In bacterial membrane-like environments, this peptide formed an α-helix amphipathic structure. Within 4 h, a reduction in the number of S. epidermidis colonies was observed, demonstrating the fast action of this peptide. As a preliminary test, a BiF2_5K7K-coated catheter was able to prevent the development of S. epidermidis biofilm both on the catheter surface and in its surrounding area.

CONCLUSIONS

Due to the safety and effectiveness of BiF2_5K7K, we suggest that this peptide be further developed to combat biofilm infections, particularly those of biofilm-forming S. epidermidis.

Synergistic effects of nano curcumin mediated photodynamic inactivation and nano-silver@colistin against Pseudomonas aeruginosa biofilms

BACKGROUND

Patients with burn injuries colonized by multidrug-resistant Pseudomonas aeruginosa face increased mortality risk. The efficacy of colistin, a last-resort treatment, is declining as resistance levels rise. P. aeruginosa's robust biofilm exacerbates antibiotic resistance. Photodynamic Inactivation (PDI) shows promise in fighting biofilm.

MATERIALS AND METHODS

Nano curcumin (nCur) particles were synthesized, and their chemical characteristics were determined using zeta potential (ZP), dynamic light scattering analysis (DLS), energy-dispersive X-ray (EDX) analysis, and fourier transform infrared (FTIR). We conducted an MTT assay to assess the cytotoxicity of nCur-mediated PDI in combination with nanosilver colistin. The fractional biofilm inhibitory concentration (FBIC) of two P. aeruginosa clinical isolates and P. aeruginosa ATCC 27853 during nCur-mediated PDI@AgNPs@CL was determined using a 3-dimensional (3-D) checkerboard assay. To study the effect of nCur-mediated PDI@AgNPs@CL on lasI, lasR, rhlI, rhlR, pelA, and pslA gene expression, Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was conducted at each isolate's FBIC. The impact of treatments was also investigated using scanning electron microscopy (SEM).

RESULTS

The ZP and mean DLS values of the nCur were 10.3 mV and 402.6 ± 24.6 nm, respectively. The distinct functional groups of nCur corresponded with the peaks of FTIR absorption. Moreover, the EDX analysis showed the ratios of different metals in nCur. Cell viability percentages of nCur-mediated PDI@AgNPs@CL at FBIC concentrations of clinical isolates Nos. 30, 354, and P. aeruginosa ATCC 27853 were 91.36 %, 83.20 %, and 92.48 %, respectively. nCur-mediated PDI@AgNPs@CL treatment showed synergistic effects in clinical isolates and P. aeruginosa ATCC 27853 in a 3-D checkerboard assay. All six of the investigated genes showed down-regulation after nCur-mediated PDI@AgNPs@CL treatment. The most suppressed gene during nCur-mediated PDI@AgNPs@CL treatment was the rhlR gene (-11.9-fold) of P. aeruginosa ATCC 27853. The SEM micrographs further proved the connecting cement reduction and biofilm mass mitigation following nCur-mediated PDI@AgNPs@CL treatments.

CONCLUSIONS

The combined effect of nCur-mediated PDI and AgNPs@CL synergistically reduce the formation of biofilm in P. aeruginosa. This may be attributable to the suppression of the genes responsible for regulating the production of biofilms.

Effects of Synthetic Tetronamides and Methylated Denigrins on Bacterial Quorum Sensing and Biofilm Formation

Detrimental biofilms of bacterial pathogens cause chronic infections with a high-level tolerance to antibiotics. To identify new control agents, we synthesized and tested a total of 14 tetronamides (including 5 new compounds) and 6 denigrin intermediates on the model species Escherichia coli. At a concentration of 50 μg/mL, two tetronamides and two methylated denigrins exhibited significant inhibitory effects against biofilm formation of E. coli RP437, e.g., by 60 and 94%, respectively. Structural analysis of the tested compounds revealed that p-methoxybenzylidene and p-methoxyphenethyl moieties of denigrins are important for biofilm inhibition, while the former group is also essential to the activity against quorum sensing (QS) via AI-2. Specifically, tetramethyldenigrin B has strong inhibitory effects against both E. coli biofilm formation and AI-2-mediated QS and thus provides a promising lead structure for designing better control agents. Consistently, tetramethyldenigrin B also showed inhibitory activity against biofilm formation of uropathogenic E. coli. Together, these findings provide new insights for the rational design of novel biofilm and QS inhibitors.

Fighting Pseudomonas aeruginosa Infections: Antibacterial and Antibiofilm Activity of D-Q53 CecB, a Synthetic Analog of a Silkworm Natural Cecropin B Variant

Pseudomonas aeruginosa is an opportunistic Gram-negative bacterium responsible for severe nosocomial infections and is considered a critical pulmonary pathogen for both immunocompromised and cystic fibrosis patients. Planktonic cells of P. aeruginosa possess intrinsic and acquired resistances, inactivating several classes of conventional antibiotics. Additionally, this bacterium can grow, forming biofilms, and complex structures, further hampering the action of multiple antibiotics. Here, we report the biological properties of D-Q53 CecB, an all-D enantiomer of the silkworm natural peptide Q53 CecB. Compared to the L-variant, D-Q53 CecB was resistant to in vitro degradation by humans and P. aeruginosa elastases and showed an enhanced bactericidal activity against P. aeruginosa planktonic bacteria. D-Q53 CecB was thermostable and maintained its antimicrobial activity at high salt concentrations and in the presence of divalent cations or fetal-bovine serum, although at reduced levels. Against different types of human cells, D-Q53 CecB showed cytotoxic phenomena at concentrations several folds higher compared to those active against P. aeruginosa. When L- and D-Q53 CecB were compared for their antibiofilm properties, both peptides were active in inhibiting biofilm formation. However, the D-enantiomer was extremely effective in inducing biofilm degradation, suggesting this peptide as a favorable candidate in an anti-Pseudomonas therapy.

Sitagliptin attenuates Porphyromonas gingivalis virulence and inflammatory response in macrophage on titanium

BACKGROUND

In peri-implantitis, Porphyromonas gingivalis and macrophage play important roles. The aim of this study was to detect the attenuating effect of an anti-diabetic drug sitagliptin on Porphyromonas gingivalis virulence and inflammatory response in macrophage on titanium discs.

MATERIALS AND METHODS

Porphyromonas gingivalis and macrophage were cultured on titanium discs. Antibacterial and antibiofilm activities of sitagliptin were assessed and the morphology of Porphyromonas gingivalis was observed by SEM. Bacterial early adhesion, aggregation, hemolysis and Porphyromonas gingivalis virulence factors mRNA expression were assessed to preliminarily investigate the mechanisms of action. Flow cytometry assay, qRT-PCR assay and ELISA were used to assess the anti-inflammatory effect of sitagliptin on Porphyromonas gingivalis lipopolysaccharide-stimulated macrophage.

RESULTS

The present study demonstrated the inhibiting effect of sitagliptin on the growth, biofilm and virulence factors of Porphyromonas gingivalis and the protective effect on the Porphyromonas gingivalis lipopolysaccharide-induced polarization in macrophage. And we also confirmed the anti-inflammatory effect of sitagliptin on the secretion of inflammation-related factors in macrophage.

CONCLUSIONS

Sitagliptin possesses the attenuating effect on Porphyromonas gingivalis virulence and inflammatory response in Porphyromonas gingivalis lipopolysaccharide-stimulated macrophage on titanium.

Bioactive compounds: a goldmine for defining new strategies against pathogenic bacterial biofilms?

Most human infectious diseases are caused by microorganisms growing as biofilms. These three-dimensional self-organized communities are embedded in a dense matrix allowing microorganisms to persistently inhabit abiotic and biotic surfaces due to increased resistance to both antibiotics and effectors of the immune system. Consequently, there is an urgent need for novel strategies to control biofilm-associated infections. Natural products offer a vast array of chemical structures and possess a wide variety of biological properties; therefore, they have been and continue to be exploited in the search for potential biofilm inhibitors with a specific or multi-locus mechanism of action. This review provides an updated discussion of the major bioactive compounds isolated from several natural sources - such as plants, lichens, algae, microorganisms, animals, and humans - with the potential to inhibit biofilm formation and/or to disperse established biofilms by bacterial pathogens. Despite the very large number of bioactive products, their exact mechanism of action often remains to be clarified and, in some cases, the identity of the active molecule is still unknown. This knowledge gap should be filled thus allowing development of these products not only as novel drugs to combat bacterial biofilms, but also as antibiotic adjuvants to restore the therapeutic efficacy of current antibiotics.

Comparative study of effective antibiofilm activity of beneficial microbes-mediated zirconia nanoparticles

In the present study, beneficial microbes-mediated zirconia nanoparticles were prepared using endophytic bacteria isolated from the seed of Terminalia chebula which were evaluated on inhibition of bacterial adherence and promotion to exhibit antibiofilm properties. The structure and distribution of the zirconia nanoparticles were examined through SEM (Scanning Electron Microscopy), EDS (Energy-Dispersive X-Ray spectroscopy), and XRD (X-ray diffraction analysis), which reveal the distribution of the particles. The morphology of biogenic zirconia nanoparticles was monoclinic and cubic. The formation of zirconia particle was confirmed using UV spectrum and the functional groups were intensified in FTIR (Fourier-transform infrared spectroscopy). The antibiofilm activity of the synthesized nanoparticles was tested in oral pathogens that cause biofilm by membrane integrity and leads to periodontal associated disease. The results showed that the particles had a significant effect on biofilm removal caused by oral pathogens. For determined concentration, the cytotoxicity of the endophytic bacterial facilitated zirconia nanoparticle (Zr NPs) was examined in HGF (Human gingival fibroblast cell line).

Antimicrobial activity and mechanisms of a derived antimicrobial peptide TroNKL-27 from golden pompano (Trachinotus ovatus) NK-lysin

NK-lysin, a homologue of granulysin among human, is predominantly found in natural killer cells and cytotoxic T-lymphocytes, which plays a pivotal part in innate immune responses against diverse pathogenic bacteria. Nonetheless, in teleosts, the research on antimicrobial activity and mechanisms of NK-lysin are seldom reported. In this study, we determined the antimicrobial activity of the truncated peptide TroNKL-27 that derived from golden pompano (Trachinotus ovatus) NK-lysin, and investigated its antimicrobial mechanisms. The results showed that TroNKL-27 had considerable antimicrobial potency against both Gram-positive (Staphylococcus aureus, Streptococcus agalactiae) and Gram-negative bacteria (Vibrio harveyi, V. alginolyticus, Escherichia coli, Edwardsiella tarda). Cytoplasmic membrane depolarization and propidium iodide (PI) uptake assay manifested that TroNKL-27 could induce the bacterial membrane depolarization and change its membrane permeability, respectively. In the light of scanning electron microscopy (SEM) observation, TroNKL-27 was capable of altering morphological structures of bacteria and leading to leakage of cellular contents. Moreover, the results of gel retardation assay indicated TroNKL-27 had the ability to induce the degradation of bacterial genomic DNA. As regards in vivo assay, TroNKL-27 could reduce the replication of V. harveyi in tissues of golden pompano, protect the tissue from pathological changes. Moreover, TroNKL-27 in vivo could significantly increase the expression of the immune genes (such as IL1β, TNFα, IFN-γ, C3 and Mx) in presence or absence of V. harveyi infection. All of these results suggest that TroNKL-27 is a novel antimicrobial peptide possessing antibacterial and immunoregulatory function in vivo and in vitro, and the observed effects of TroNKL-27 will lay a solid foundation for the development of new antimicrobial agents used in aquaculture.

Discovery of a Novel Antimicrobial Peptide, Temporin-PKE, from the Skin Secretion of Pelophylax kl. esculentus, and Evaluation of Its Structure-Activity Relationships

Bacterial resistance against antibiotics has led to increasing numbers of treatment failures, and AMPs are widely accepted as becoming potential alternatives due to their advantages. Temporin-PKE is a novel peptide extracted from the skin secretion of Pelophylax kl. esculentus and it displays a strong activity against Gram-positive bacteria, with an extreme cytotoxicity. Incorporating positively charged residues and introducing D-amino acids were the two main strategies adopted for the modifications. The transformation of the chirality of Ile could reduce haemolytic activity, and an analogue with appropriate D-isoforms could maintain antimicrobial activity and stability. The substitution of hydrophobic residues could bring about more potent and broad-spectrum antimicrobial activities. The analogues with Lys were less harmful to the normal cells and their stabilities remained at similarly high levels compared to temporin-PKE. The optimal number of charges was three, and the replacement on the polar face was a better choice. Temporin-PKE-3K exerted dually efficient functions includingstrong antimicrobial and anticancer activity. This analogue showed a reduced possibility for inducing resistance in MRSA and Klebsiella pneumoniae, a rather strong antimicrobial activity in vivo, and it exhibited the highest therapeutic index such that temporin-PKE-3K has the potential to be developed as a clinical drug.

Application of Ginsenoside Rd in Periodontitis With Inhibitory Effects on Pathogenicity, Inflammation, and Bone Resorption

Periodontitis is a worldwide oral disease induced by the interaction of subgingival bacteria and host response and is characterized by local inflammation, bone resorption, and tooth loss. Ginsenoside Rd (Rd) is a biologically active component derived from Panax ginseng and has been demonstrated to exert antibacterial and anti-inflammatory activities. This study aims to investigate the inhibitory efficiency of Rd towards Porphyromonas gingivalis (P. gingivalis), periodontal inflammatory response, and osteoclastogenesis in vitro and to further validate the results in a mouse periodontitis model, thus, evaluate the potential effects of Rd on the control and prevention of periodontitis. According to the results, Rd exerted excellent antibacterial activities against planktonic P. gingivalis, along with attenuating P. gingivalis virulence and inhibiting its biofilms. Meanwhile, the inflammatory cytokine production and osteoclastogenesis were remarkably inhibited by Rd both in vitro and in vivo. Furthermore, Rd efficiently ameliorated the subgingival P. gingivalis abundance and suppressed the alveolar bone resorption in vivo as well. In conclusion, Rd has the potential to be developed as a promising medication in the control and prevention of periodontitis.

Four temporin-derived peptides exhibit antimicrobial and antibiofilm activities against methicillin-resistant

Temporin-GHa (GHa) was cloned from , showing a weak antimicrobial activity. In order to improve its bactericidal efficacy, GHaR6R, GHaR7R, GHaR8R and GHaR9W were designed and synthesized. Compared to the parent peptide, the GHa-derived peptides show potent antimicrobial activities against methicillin-resistant (MRSA), which is the main pathogen with high morbidity and mortality that causes various infections in humans. These peptides exert bactericidal actions on MRSA by permeabilizing the cytoplasmic membranes and damaging membrane integrity. All of the four peptides exhibit excellent stability under harsh conditions, including extreme temperature and salts. Furthermore, they inhibit the formation of biofilm and eradicate mature biofilm of MRSA. The GHa-derived peptides decrease bacterial surface hydrophobicity, autoaggregation and polysaccharide intercellular adhesion synthesis in concentration-dependent manner. Real-time quantitative reverse transcription PCR analysis revealed that the peptides downregulate the expression of adhesion genes involved in biofilm formation. Except for GHaR7R, the other three peptides have low hemolytic toxicity against human erythrocytes. In the presence of human erythrocytes, GHaR7R, GHaR8R and GHaR9W interact with MRSA preferentially. GHaR6R, GHaR8R and GHaR9W show less toxicity toward normal cells HL-7702 and hFOB1.19. These results suggest that the GHa-derived peptides may be promising antimicrobial candidates against MRSA infections.

Bioevaluation and Targeted Modification of Temporin-FL From the Skin Secretion of Dark-Spotted Frog (Pelophylax nigromaculatus)

Bioactive proteins secreted by the granular glands of amphibian skin play a self-defensive role, and exhibit various bioactivities in vitro and in vivo. In light of the severity of the problem of antibiotic resistance for treating infections, many antimicrobial peptides (AMPs) have been developed and applied in clinical microbial treatments. We identified a naturally derived and potent antimicrobial peptide, temporin-FL, obtained from the skin secretion of Pelophylax nigromaculatus via “shotgun” cloning. Two truncated analogues of this peptide were chemically synthesized to explore their structural-functional relationships. The results of a functional evaluation showed that all of the tested AMPs were active against Gram-positive bacteria and fungi and demonstrated antibiofilm activity against methicillin-resistant Staphylococcus aureus (MRSA) but did not have an effect on Gram-negative bacteria. Moreover, temporin-FLa demonstrated a higher level of hydrophobicity and enhanced antimicrobial efficiency, as well as hemolytic activity and cell cytotoxicity than the parent peptide. Temporin-FLb, which evidenced significantly less α-helicity, was less potent against various microbes but exhibited lower cytotoxicity relating to mammalian cells. Both of the synthesized analogues possessed a higher therapeutic index than the original peptide. Moreover, the membrane permeability assay and the measuring membrane depolarization assay declared that temporin-FL and its analogues induced membrane fracture and depolarization; the quantitative biofilm formation assay and the observations of MRSA biofilms using scanning electron microscopy revealed that the AMPs caused biofilm disruption and blocked biofilm formation, the former experiments all confirming their antimicrobial and antibiofilm properties. Hence, the optimization of temporin-FL offers insights for the discovery of new drugs for treating MRSA infections.

Aggregation and Its Influence on the Bioactivities of a Novel Antimicrobial Peptide, Temporin-PF, and Its Analogues

Temporin is an antimicrobial peptide (AMP) family discovered in the skin secretion of ranid frog that has become a promising alternative for conventional antibiotic therapy. Herein, a novel temporin peptide, Temporin-PF (TPF), was successfully identified from Pelophylax fukienensis. It exhibited potent activity against Gram-positive bacteria, but no effect on Gram-negative bacteria. Additionally, TPF exhibited aggregation effects in different solutions. Three analogs were further designed to study the relationship between the aggregation patterns and bioactivities, and the MD simulation was performed for revealing the pattern of the peptide assembly. As the results showed, all peptides were able to aggregate in the standard culture media and salt solutions, especially CaCl2 and MgCl2 buffers, where the aggregation was affected by the concentration of the salts. MD simulation reported that all peptides were able to form oligomers. The parent peptide assembly depended on the hydrophobic interaction via the residues in the middle domain of the sequence. However, the substitution of Trp/D-Trp resulted in an enhanced inter-peptide interaction in the zipper-like domain and eliminated overall biological activities. Our study suggested that introducing aromaticity at the zipper-like domain for temporin may not improve the bioactivities, which might be related to the formation of aggregates via the inter-peptide contacts at the zipper-like motif domain, and it could reduce the binding affinity to the lipid membrane of microorganisms.

An Overview of Biological and Computational Methods for Designing Mechanism-Informed Anti-biofilm Agents

Bacterial biofilms are complex and highly antibiotic-resistant aggregates of microbes that form on surfaces in the environment and body including medical devices. They are key contributors to the growing antibiotic resistance crisis and account for two-thirds of all infections. Thus, there is a critical need to develop anti-biofilm specific therapeutics. Here we discuss mechanisms of biofilm formation, current anti-biofilm agents, and strategies for developing, discovering, and testing new anti-biofilm agents. Biofilm formation involves many factors and is broadly regulated by the stringent response, quorum sensing, and c-di-GMP signaling, processes that have been targeted by anti-biofilm agents. Developing new anti-biofilm agents requires a comprehensive systems-level understanding of these mechanisms, as well as the discovery of new mechanisms. This can be accomplished through omics approaches such as transcriptomics, metabolomics, and proteomics, which can also be integrated to better understand biofilm biology. Guided by mechanistic understanding, in silico techniques such as virtual screening and machine learning can discover small molecules that can inhibit key biofilm regulators. To increase the likelihood that these candidate agents selected from in silico approaches are efficacious in humans, they must be tested in biologically relevant biofilm models. We discuss the benefits and drawbacks of in vitro and in vivo biofilm models and highlight organoids as a new biofilm model. This review offers a comprehensive guide of current and future biological and computational approaches of anti-biofilm therapeutic discovery for investigators to utilize to combat the antibiotic resistance crisis.

Temporin-Like Peptides Show Antimicrobial and Anti-Biofilm Activities against Streptococcus mutans with Reduced Hemolysis

In our previous study, temporin-GHaR (GHaR) showed potent antimicrobial activity with strong hemolytic toxicity. To overcome its weakness, we designed GHaR6R, GHaR7R, GHaR8R, GHaR9R, and GHaR9W by changing the number of positive charges and the hydrophobic surface of GHaR. With the exception of GHaR7R, the hemolytic toxicity of the derived peptides had been reduced, and the antimicrobial activities remained close to the parent peptide (except for GHaR9R). GHaR6R, GHaR7R, GHaR8R, and GHaR9W exhibited a great bactericidal effect on Streptococcus mutans (S. mutans), which is one of the main pathogens causing dental caries. According to the membrane permeation and scanning electron microscope (SEM) analysis, these derived peptides targeted to the cell membranes of planktonic bacteria, contributing to the disruption of the membrane integrity and leakage of the intracellular contents. Moreover, they inhibited the formation of biofilms and eradicated the mature biofilms of S. mutans. Compared with GHaR7R, the derived peptides showed less cytotoxicity to human oral epithelial cells (HOECs). The derived peptides are expected to be the molecular templates for designing antibacterial agents to prevent dental caries.

Propolis nanoparticle enhances the potency of antimicrobial photodynamic therapy against Streptococcus mutans in a synergistic manner

Less invasive removal approaches have been recommended for deep caries lesions. Antimicrobial photodynamic therapy (aPDT) and propolis nanoparticle (PNP) are highlighted for the caries management plan. Evidence is lacking for an additive effect of combination PNP with photosensitizer (PS) in aPDT. This study aimed to investigate the individual and synergistic effects of chlorophyllin-phycocyanin mixture (PhotoActive⁺) and toluidine blue O (TBO) as PSs in combination with PNP in the aPDT process (aPDT^plus) against major important virulence factors of Streptococcus mutans. Following characterization, biocompatibility of the PSs alone, or in combination with PNP were investigated on human gingival fibroblast cell. The in vitro synergy of PhotoActive⁺ or TBO and PNP was evaluated by the checkerboard method. The bacteria's virulence properties were surveyed in the presence of the PSs, individually as well as in combination. When the PSs were examined in combination (synergistic effect, FIC Index < 0.5), a stronger growth inhibitory activity was exhibited than the individual PSs. The biofilm formation, as well as genes involved in biofilm formation, showed greater suppression when the PSs were employed in combination. Overall, the results of this study suggest that the combination of PhotoActive⁺ or TBO with PNP with the least cytotoxicity effects and the highest antimicrobial activites would improve aPDT outcomes, leading to synergistic effects and impairing the virulence of S. mutans.

Targeting Biofilms Therapy: Current Research Strategies and Development Hurdles

Biofilms are aggregate of microorganisms in which cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) and adhere to each other and/or to a surface. The development of biofilm affords pathogens significantly increased tolerances to antibiotics and antimicrobials. Up to 80% of human bacterial infections are biofilm-associated. Dispersal of biofilms can turn microbial cells into their more vulnerable planktonic phenotype and improve the therapeutic effect of antimicrobials. In this review, we focus on multiple therapeutic strategies that are currently being developed to target important structural and functional characteristics and drug resistance mechanisms of biofilms. We thoroughly discuss the current biofilm targeting strategies from four major aspects—targeting EPS, dispersal molecules, targeting quorum sensing, and targeting dormant cells. We explain each aspect with examples and discuss the main hurdles in the development of biofilm dispersal agents in order to provide a rationale for multi-targeted therapy strategies that target the complicated biofilms. Biofilm dispersal is a promising research direction to treat biofilm-associated infections in the future, and more in vivo experiments should be performed to ensure the efficacy of these therapeutic agents before being used in clinic.

A Textile Pile Debridement Material Consisting of Polyester Fibers for in Vitro Removal of Biofilm

Biofilms formed on skin wound lead to inflammation and a delay of healing. In the present work, a novel textile pile debridement material was prepared and treated by plasma. Samples before and after plasma treatment were characterized by a series of methods, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and water uptake capacity. Besides, mechanical, coagulation, and in vitro biofilm removal performances of the textile pile debridement material were evaluated, with a medical gauze as a control. The results demonstrate that the plasma treatment produced corrosions and oxygen-containing polar groups on the fiber surface, offering an enhanced water uptake capacity of the textile pile debridement material. In addition, compressive tests certify the mechanical performances of the textile pile debridement material in both dry and wet conditions. The results from a kinetic clotting time test suggest a favorable ability to promote blood coagulation. Furthermore, the results of an MTT cell viability assay, SEM, and confocal laser scanning microscopy (CLSM) illustrate that the textile pile debridement material demonstrates a more superior in vitro biofilm removal performance than medical gauze. All of these characterizations suggest that the textile pile debridement material can offer a feasible application for clinical wound debridement.