Rapid Bactericidal Effect Research Articles

Ru(II) Complexes with Enaminone Structures for Rapid Sterilization of Staphylococcus aureus and MRSA with Little Accumulation of Drug Resistance.

Drug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), pose a serious threat to human life. Therefore, there is urgent need to develop antibiotics with new chemical structures and antibacterial mechanisms, especially those that elicit little drug resistance after long-term use. Herein we synthesized three novel ruthenium complexes (Ru1-Ru3) containing the enaminone structures for the first time. At a concentration of 5 μM, Ru1-Ru3 can lead to a CFU reduction of about 5 log units towards S. aureus and MRSA. Interestingly, Ru3 displayed rapid bactericidal effects and could decrease the CFU numbers of both pathogens by 5 log units within 40 min. The control compounds (Ru4 and Ru5) without the enaminone structures displayed very poor antibacterial activity under the same conditions. Moreover, S. aureus did not show apparent drug resistance towards Ru3 after 20 passages incubation with a sublethal concentration. These results highlight the critical role of enaminone structures for antibacterial applications.

Membrane-Targeting Neolignan-Antimicrobial Peptide Mimic Conjugates to Combat Methicillin-Resistant Staphylococcus aureus (MRSA) Infections.

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) continue to endanger public health. Here, we report the synthesis of neolignan isomagnolone (I) and its isomer II, and the preparation of a series of novel neolignan-antimicrobial peptide (AMP) mimic conjugates. Notably, conjugates III5 and III15 exhibit potent anti-MRSA activity in vitro and in vivo, comparable to that of vancomycin, a current effective treatment for MRSA. Moreover, III5 and III15 display not only fast-killing kinetics and low resistance frequency but also low toxicity as well as effects on bacterial biofilms. Mechanism studies reveal that III5 and III15 exhibit rapid bactericidal effects through binding to the phosphatidylglycerol (PG) and cardiolipin (CL) of the bacterial membrane, thereby disrupting the cell membranes and allowing increased reactive oxygen species (ROS) as well as protein and DNA leakage. The results indicate that these neolignan-AMP mimic conjugates could be promising antimicrobial candidates for combating MRSA infections.

Synthesis and Antimicrobial Activity of Short Analogues of the Marine Antimicrobial Peptide Turgencin A: Effects of SAR Optimizations, Cys-Cys Cyclization and Lipopeptide Modifications.

We have synthesised short analogues of the marine antimicrobial peptide Turgencin A from the colonial Arctic ascidian Synoicum turgens. In this study, we focused on a central, cationic 12-residue Cys-Cys loop region within the sequence. Modified (tryptophan- and arginine-enriched) linear peptides were compared with Cys-Cys cyclic derivatives, and both linear and Cys-cyclic peptides were N-terminally acylated with octanoic acid (C8), decanoic acid (C10) or dodecanoic acid (C12). The highest antimicrobial potency was achieved by introducing dodecanoic acid to a cyclic Turgencin A analogue with low intrinsic hydrophobicity, and by introducing octanoic acid to a cyclic analogue displaying a higher intrinsic hydrophobicity. Among all tested synthetic Turgencin A lipopeptide analogues, the most promising candidates regarding both antimicrobial and haemolytic activity were C12-cTurg-1 and C8-cTurg-2. These optimized cyclic lipopeptides displayed minimum inhibitory concentrations of 4 µg/mL against Staphylococcus aureus, Escherichia coli and the fungus Rhodothorula sp. Mode of action studies on bacteria showed a rapid membrane disruption and bactericidal effect of the cyclic lipopeptides. Haemolytic activity against human erythrocytes was low, indicating favorable selective targeting of bacterial cells.

Novel Feleucin-K3-Derived Peptides Modified with Sulfono-γ-AA Building Blocks Targeting Pseudomonas aeruginosa and Methicillin-Resistant Staphylococcus aureus Infections.

The prevalence of multidrug-resistant bacterial infections has led to dramatically increased morbidity and mortality. Antimicrobial peptides (AMPs) have great potential as new therapeutic agents to reverse this dangerous trend. Herein, a series of novel AMP Feleucin-K3 analogues modified with unnatural peptidomimetic sulfono-γ-AA building blocks were designed and synthesized. The structure-activity, structure-toxicity, and structure-stability relationships were investigated to discover the optimal antimicrobial candidates. Among them, K122 exhibited potent and broad-spectrum antimicrobial activity and high selectivity. K122 had a rapid bactericidal effect and a low tendency to induce resistance. Surprisingly, K122 showed excellent effectiveness against bacterial pneumonia. For biofilm and local skin infections, K122 significantly decreased the bacterial load and improved tissue injury at a dose of only 0.25 mg/kg, which was 160 times lower than the concentration deemed to be safe for local dermal applications. In summary, K122 is an outstanding candidate for the treatment of multidrug-resistant bacteria and biofilm infections.

A Highly Efficient Polystyrene-Based Cationic Resin to Reduce Bacterial Contaminations in Water

Nowadays, new water disinfection materials attract a lot of attention for their cost-saving and ease of application. Nevertheless, the poor durability of the matrices and the loss of physically incorporated or chemically attached antibacterial agents that can occur during water purification processes considerably limit their prolonged use. In this study, a polystyrene-based cationic resin (R4) with intrinsic broad-spectrum antibacterial effects was produced without needing to be enriched with additional antibacterial agents that could detach during use. Particularly, R4 was achieved by copolymerizing 4-ammonium-butyl-styrene (4-ABSTY) with N,N-dimethylacrylamide (DMAA) and using N-(2-acryloylamino-ethyl)-acrylamide (AAEA) as a cross-linker. The R4 obtained showed a spherical morphology, micro-dimensioned particles, high hydrophilicity, high-level porosity, and excellent swelling capabilities. Additionally, the swollen R4 to its maximum swelling capability, when dried with gentle heating for 3 h, released water following the Higuchi's kinetics, thus returning to the original structure. In time-kill experiments on the clinical isolates of multidrug-resistant (MDR) pathogens of fecal origin, such as enterococci, Group B Salmonella species, and Escherichia coli, R4 showed rapid bactericidal effects on enterococci and Salmonella, and reduced E. coli viable cells by 99.8% after 4 h. When aqueous samples artificially infected by a mixture of the same bacteria of fecal origin were exposed for different times to R4 in a column, simulating a water purification system, 4 h of contact was sufficient for R4 to show the best bacterial killing efficiency of 99%. Overall, thanks to its physicochemical properties, killing efficiency, low costs of production, and scalability, R4 could become a cost-effective material for building systems to effectively reduce bacterial, even polymicrobial, water contamination.

In vitro activities of licochalcone A against planktonic cells and biofilm of Enterococcus faecalis

This study aims to evaluate the in vitro antibacterial and anti-biofilm activities of licochalcone A on Enterococcus faecalis and to investigate the possible target genes of licochalcone A in E. faecalis. This study found that licochalcone A had antibacterial activities against E. faecalis, with the MIC50 and MIC90 were 25 μM. Licochalcone A (at 4 × MIC) indicated a rapid bactericidal effect on E. faecalis planktonic cells, and killed more E. faecalis planktonic cells (at least 3-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 2, 4, and 6 h of the time-killing test. Licochalcone A (at 10 × MIC) significantly reduced the production of E. faecalis persister cells (at least 2-log10 cfu/ml) than vancomycin, linezolid, or ampicillin at the 24, 48, 72, and 96 h of the time-killing test. Licochalcone A (at 1/4 × MIC) significantly inhibited the biofilm formation of E. faecalis. The RNA levels of biofilm formation-related genes, agg, esp, and srtA, markedly decreased when the E. faecalis isolates were treated with licochalcone A at 1/4 × MIC for 6 h. To explore the possible target genes of licochalcone A in E. faecalis, the licochalcone A non-sensitive E. faecalis clones were selected in vitro by induction of wildtype strains for about 140 days under the pressure of licochalcone A, and mutations in the possible target genes were detected by whole-genome sequencing. This study found that there were 11 nucleotide mutations leading to nonsynonymous mutations of 8 amino acids, and among these amino acid mutations, there were 3 mutations located in transcriptional regulator genes (MarR family transcriptional regulator, TetR family transcriptional regulator, and MerR family transcriptional regulator). In conclusion, this study found that licochalcone A had an antibacterial effect on E. faecalis, and significantly inhibited the biofilm formation of E. faecalis at subinhibitory concentrations.

Antibacterial Effect and Possible Mechanism of Salicylic Acid Microcapsules against Escherichia coli and Staphylococcus aureus.

Microcapsules serve as a feasible formulation to load phenolic substances such as salicylic acid, a natural and safe antimicrobial agent. However, the antibacterial efficacy of salicylic acid microcapsules (SAMs) remains to be elucidated. Here, salicylic acid/β-cyclodextrin inclusion microcapsules were subjected to systematic antibacterial assays and preliminary antibacterial mechanism tests using Escherichia coli and Staphylococcus aureus as target organisms. It was found that the core-shell rhomboid-shaped SAMs had a smooth surface. SAMs exhibited a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 4 mg/mL against both bacteria. In the growth inhibition assay, 1/4 × MIC, 1/2 × MIC, and 1 × MIC of SAMs effectively retarded bacterial growth, and this effect was more prominent with the rise in the level of SAMs. Practically, SAMs possessed a rapid bactericidal effect at the 1 × MIC level with a reduction of more than 99.9% bacterial population within 10 min. A pronounced sterilization activity against E. coli and S. aureus was also observed when SAMs were embedded into hand sanitizers as antimicrobial agents. Moreover, exposure of both bacteria to SAMs resulted in the leakage of intracellular alkaline phosphatases and macromolecular substances (nucleic acids and proteins), which indicated the disruption of bacterial cell walls and cell membranes. In conclusion, SAMs were able to inactivate E. coli and S. aureus both in vitro and in situ, highlighting the promising utilization of this formulation for antimicrobial purposes in the area of food safety and public health.

Antibiotics for multidrug-resistant gram-positive bacteria

Background: Antimicrobial resistance is a major global threat to public health and is associated with increased morbidity and mortality. A few therapeutic options for the treatment of multidrug resistant (MDR) gram-positive bacteria, such as methicillin resistant Staphylococcus aureus, MDR Streptococcus pneumoniae, vancomycin resistant Enterococci, are available.Current Concepts: As a result of comprehensive efforts, a dozen novel antibiotics have been developed and approved for the treatment of MDR gram-positive bacteria in the United States and Europe over the past 15 years. However, only a few antibiotics have been introduced in the Republic of Korea. The purpose of this review is to evaluate the antibiotics that act against MDR gram-positive bacteria as a primary therapeutic option. Particularly, this review focuses on novel antibiotics, including ceftaroline, ceftobiprole, telavancin, dalbavancin, oritavancin, tedizolid, delafloxacin, omadacycline, and lefamulin.Discussion and Conclusion: Novel antibiotics against MDR gram-positive bacteria have not yet been sufficiently studied in various clinical settings, and therefore, the approved indications are limited. However, these antibiotics are expected to play a major role in the treatment of MDR gram-positive bacteria owing to their advantages, including broad anti-bacterial spectrum, rapid bactericidal effect, minimal drug-drug interaction, a favorable safety profile, availability of both intravenous and oral formulations, convenient dosing scheme, and a single dose (or once a week) regimen owing to long half-life. It is crucial to introduce these novel antibiotics in the Republic of Korea for the treatment of patients suffering from MDR bacterial infections.

Isobavachalcone From Cullen corylifolium Presents Significant Antibacterial Activity Against Clostridium difficile Through Disruption of the Cell Membrane.

Background: Clostridium difficile infection (CDI) has been widely reported in human and animals around the world over the past few decades. The high relapse rate and increasing drug resistance of CDI make the discovery of new agents against C. difficile fairly urgent. This study aims to investigate the antibacterial activity against C. difficile from traditional Chinese herb medicine Cullen corylifolium and confirm its active components. Methods: Phenolic extract from the seeds of C. corylifolium was prepared routinely and the contents of relative flavonoids were determined by High Performance Liquid Chromatography (HPLC). In vitro antibacterial activities of the phenolic extract and its major components were tested. The influence of the major components on cell membrane was investigated with membrane integrity by SEM and propidium iodid uptake assay. Cytotoxicity of the extract and its active compounds on Caco-2 cell line was assessed by CCK-8 kit. The in vivo therapeutic efficacy of IBCL was evaluated on the mice model. Results: Phenolic extract was found to be active against C. difficile with minimum inhibitory concentrations (MIC) of 8 μg/mL. As the major component of the extract, IBCL was the most active compound against C. difficile. The MIC of IBCL and 4MBCL were 4 μg/ml and 4 μg/ml, respectively. Meanwhile, PFPE, IBCL, and 4MBCL showed rapid bactericidal effect against C. difficile in 1 h, which was significant compared to antibiotic vancomycin. Mechanism studies revealed that IBCL can disrupt the integrity of the cell membrane, which may lead to the death of bacteria. PFPE was low cytotoxic against Caco-2 cells, and the cytotoxicity of IBCL and 4MBCL were moderate. Symptoms of CDI were effectively alleviated by IBCL on the mice model and weight loss was reduced. From death rates, IBCL showed better efficacy compared to vancomycin at 50 mg/kg dosage. Conclusion: As the major component of phenolic extract of C. corylifolium seeds, IBCL showed significant antibacterial activity against C. difficile in vitro and rapidly killed the bacteria by disrupting the integrity of the cell membrane. IBCL can significantly prevent weight loss and reduce death caused by CDI on the mice model. Therefore, IBCL may be a promising lead compound or drug candidate for CDI.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity

Background & Objective: The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques.Methods: Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results: Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively).Conclusion: BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

Synthesis and Antibacterial Activity of Manganese-Ferrite/Silver Nanocomposite Combined with Two Essential Oils.

The antimicrobial activity of metal nanoparticles obtained by biogenic routes has been extensively reported. However, their combined use with other antimicrobial formulations, such as essential oils, remains scarcely explored. In this work, a manganese-ferrite/silver nanocomposite (MnFe2O4/Ag-NC) was synthesized in a two-step procedure: first, MnFe2O4 nanoparticles were produced by a coprecipitation method, followed by in situ biogenic reduction of silver ions using Galega officinalis. MnFe2O4/Ag-NC was characterized using transmission electron microscopy (TEM), scanning electron microscopy equipped with an energy dispersive X-ray analyzer (SEM-EDX), and a vibrating sample magnetometer (VSM-SQUID). The antibacterial activity if MnFe2O4/Ag-NC was evaluated against Pseudomonas syringae by determining its minimum inhibitory concentration (MIC) in the presence of two essential oils: eucalyptus oil (EO) and garlic oil (GO). The fractional inhibitory concentration (FIC) was also calculated to determine the interaction between MnFe2O4/Ag-NC and each oil. The MIC of MnFe2O4/Ag-NC was eightfold reduced with the two essential oils (from 20 to 2.5 µg mL−1). However, the interaction with EO was synergistic (FIC: 0.5), whereas the interaction with GO was additive (FIC: 0.75). Additionally, a time-kill curve analysis was performed, wherein the MIC of the combination of MnFe2O4/Ag-NC and EO provoked a rapid bactericidal effect, corroborating a strong synergism. These findings suggest that by combining MnFe2O4/Ag-NC with essential oils, the necessary ratio of the nanocomposite to control phytopathogens can be reduced, thus minimizing the environmental release of silver.

Antibacterial and antifungal activity of kenaf seed peptides and their effect on microbiological safety and physicochemical properties of some food models

This study aimed to develop natural antibacterial and antifungal peptides from kenaf seed powder and to determine their efficacy in prolonging the shelf-life of fruit juices and bread systems. The kenaf seed peptides mixture (KSPM) displayed potent antimicrobial activity ranging from 94.48 to 98.99% against Gram-positive and Gram-negative bacteria and fungi. Sixteen low molecular weight cationic peptides ranging from 768 to 1416 Da were identified, in which nine of them were de novo peptides. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of KSPM against gram-positive bacteria were 11 μg/mL, 22 μg/mL for gram-negative bacteria, with a higher MIC of 43 μg/mL and minimum fungicidal concentration (MFC) of 86 μg/mL required against fungi. The KSPM displayed a rapid bactericidal effect against all the tested bacteria at 1 MIC within 1 h, and a rapid fungicidal effect against all the tested fungi at 2 MIC within 4 h. The KSPM retained a 100% of its activity up to 121 °C, 100 mM NaCl and in an acidic environment, and to a lesser extent of 64–72% under neutral condition. The peptides were fully digested by gastrointestinal proteases including pepsin, trypsin and α-chymotrypsin. The incorporation of 1000 and 3000 mg/kg KSPM in bacteria-inoculated mango and pineapple juices caused a ≥5-log10 reduction in the viable counts of Salmonella typhimurium, Escherichia coli and Listeria monocytogenes within 1–2 h during storage at 4 °C. The application of KSPM at 3000 mg/kg reduced Aspergillus niger, Aspergillus flavus and Fusarium sp. count by 3–4 log10 in fungi-inoculated bread samples when stored at 25 °C. The peptides at 1000 and 3000 mg/kg successfully extended the shelf-life of bacteria-free fruit juices for 150 days, and mould-free bread for 10 and 16 days. The addition of KSPM to fruit juices and bread model did not induce alteration to their physicochemical properties. These findings demonstrating the potential application of KSPM as a natural preservative in the food industry.

Effect of hypochloric acid on Escherichia coli biofilm and the clinical efficacy of hypochloric acid for wounds with Escherichia coli infection

Effect of hypochloric acid on Escherichia coli biofilm and the clinical efficacy of hypochloric acid for wounds with Escherichia coli infection

Exploration of Bacterial Re-Growth as In Vitro Phenomenon Affecting Methods for Analysis of the Antimicrobial Activity of Chimeric Bacteriophage Endolysins.

Drug alternatives to combat methicillin-resistant Staphylococcus aureus (MRSA) in human and animal healthcare are urgently needed. Recently, the recombinant bacteriophage endolysins, PRF-119 and its successor substance HY-133, have proven to be highly active against various S. aureus clonal lineages and to exhibit a very rapid bactericidal effect when standard methods for susceptibility testing are applied. Along with subsequent growth curve experiments, a re-growth phenomenon was observed in vitro necessitating its clarification for the assessment of the agent’s stability and activity as well as for methodological aspects of endolysin testing in general. Distinct in vitro parameters were comparatively examined applying also scanning electron microscopy, fluorescence assays and SDS-PAGE analysis. The shape and material of the culture vessels as well as the shaking conditions were identified as factors influencing the in vitro stability and activity of HY-133. The highest function maintenance was observed in plain centrifuge tubes. Based on this, the conditions and parameters of assays for testing the antimicrobial activities of phage endolysins were determined and adjusted. In particular, shear forces should be kept to a minimum. Our results form the basis for both future test standardization and re-growth-independent experiments as prerequisites for exact determination of the antimicrobial activities of engineered endolysins.

Polymers as advanced antibacterial and antibiofilm agents for direct and combination therapies.

The growing prevalence of antimicrobial drug resistance in pathogenic bacteria is a critical threat to global health. Conventional antibiotics still play a crucial role in treating bacterial infections, but the emergence and spread of antibiotic-resistant micro-organisms are rapidly eroding their usefulness. Cationic polymers, which target bacterial membranes, are thought to be the last frontier in antibacterial development. This class of molecules possesses several advantages including a low propensity for emergence of resistance and rapid bactericidal effect. This review surveys the structure–activity of advanced antimicrobial cationic polymers, including poly(α-amino acids), β-peptides, polycarbonates, star polymers and main-chain cationic polymers, with low toxicity and high selectivity to potentially become useful for real applications. Their uses as potentiating adjuvants to overcome bacterial membrane-related resistance mechanisms and as antibiofilm agents are also covered. The review is intended to provide valuable information for design and development of cationic polymers as antimicrobial and antibiofilm agents for translational applications.

The Antibacterial and Anti-biofilm Traits of the Novel BMAP-27-Melittin Conjugated Peptide Nanoparticle Against Streptococcus mutans: Clinical Isolates from Oral Cavity.

Background & Objective:The spread and development of drug-resistant bacterial strains has prompted the hunt for novel antibacterial polypeptides undergoing conformational changes to confer rapid bactericidal effects. The aim of this study was to evaluate the effect of novel BMAP27-Melittin conjugated peptide- nanoparticle (NP) against Streptococcus mutans as the primary pathogen from subgingival plaques. Methods:Sixty subgingival plaque samples were collected, and 39 S. mutans isolates were identified. The BMAP27-Melittin conjugated peptide was purchased from GenScript Company, USA. Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Biofilm Inhibitory Concentration (BIC), and Biofilm Eradication Concentration (BEC) of BMAP27-Melittin-NP were calculated using the microtiter method.Results:Thirty-nine infected subjects were reported, including 24 males and 15 females (P=0.299). MIC, MBC, BIC, and BEC of BMAP27-Melittin–NP against S. mutans were 1.8, 2.9, 2.1, and 3.8μg/mL, respectively. The mean MBC, BEC, and BIC values were significantly lower among clinical isolates than S. mutans ATCC 35688 standard strain (P=0.032, 0.001, and 0.001, respectively). Conclusion:BMAP27-Melittin-NP demonstrated significant antibacterial and anti-biofilm effects against clinical isolates of S. mutans which can be considered a promising compound to prevent or treat dental caries and eradicate the oral infections.

Lactoferricin-inspired peptide AMC-109 augments the effect of ciprofloxacin against Pseudomonas aeruginosa biofilm in chronic murine wounds

Chronic wounds are characterised by prolonged inflammation, low mitogenic activity, high protease/low inhibitor activity, microbiota changes and biofilm formation, combined with the aetiology of the original insult. One strategy to promote healing is to terminate the parasitism-like relationship between the biofilm-growing pathogen and host response. Antimicrobial peptide AMC-109 is a potential treatment with low resistance potential and broad-spectrum coverage with rapid bactericidal effect. We aimed to investigate whether adjunctive AMC-109 could augment the ciprofloxacin effect in a chronic Pseudomonas aeruginosa wound model. Third-degree burns were inflicted on 33 BALB/c mice. Pseudomonas aeruginosa embedded in seaweed alginate was injected sub-eschar to mimic biofilm. Mice were randomised to receive AMC-109, combined AMC-109 and ciprofloxacin, ciprofloxacin, or placebo for 5 days followed by sample collection. A lower bacterial load was seen in the double-treated group compared with either monotherapy group (AMC-109, p=0.0076; ciprofloxacin, p=0.0266). To evaluate the innate host response, cytokines and growth factors were quantified. The pro-inflammatory response was dampened in the double-treated mice compared with the mono-ciprofloxacin-treated group (p=0.0009). Lower mobilisation of neutrophils from the bone marrow was indicated by reduced G-CSF in all treatment groups compared with placebo. Improved tissue remodelling was indicated by the highest level of tissue inhibitor of metalloproteases and low metalloprotease level in the double-treated group. AMC-109 showed adjunctive antipseudomonal abilities augmenting the antimicrobial effect of ciprofloxacin in this wound model. The study indicates a potential role for AMC-109 in treating chronic wounds with complicating biofilm infections.

Antimicrobial Activity of Phytic Acid: An Emerging Agent in Endodontics.

BackgroundPhytic acid (IP6) is a promising and emerging agent, and because of its unique structure and distinctive properties, it lends itself to several applications in dentistry. Recently, IP6 was proposed as a potential chelating agent in endodontics. However, there is limited knowledge regarding its antimicrobial and antibiofilm effectiveness. The aims of this study, were therefore to evaluate the antimicrobial and antibiofilm activities of IP6 against a range of microbial species and compare these with ethylenediaminetetraacetic acid (EDTA) and sodium hypochlorite (NaOCl). The contact time required for IP6 to exert its bactericidal effect on Enterococcus faecalis was also determined.MethodsThe inhibitory and biocidal activities of IP6, EDTA and NaOCl were assessed using a broth microdilution assay against 11 clinical and reference strains of bacteria and a reference strain of Candida albicans. The contact time required for various IP6 concentrations to eliminate planktonic cultures of E. faecalis was determined using a membrane filtration method according to BS-EN-1040:2005. IP6 bactericidal activity was also evaluated using fluorescent microscopy, and the antibiofilm activity of the test agents was also determined.ResultsIP6 was biocidal against all tested microorganisms. At concentrations of 0.5%, 1% and 2%, IP6 required 5 min to exert a bactericidal effect on E. faecalis, while 5% IP6 was bactericidal after 30 s. IP6 also eradicated biofilms of the tested microorganisms. In conclusion, IP6 had notable antimicrobial effects on planktonic and biofilm cultures and exhibited rapid bactericidal effects on E. faecalis. This research highlighted, for the first time the antimicrobial and antibiofilm properties of IP6, which could be exploited, not only in dental applications, but also other fields where novel strategies to counter antimicrobial resistance are required.

Evaluation of Short-Chain Antimicrobial Peptides With Combined Antimicrobial and Anti-inflammatory Bioactivities for the Treatment of Zoonotic Skin Pathogens From Canines.

The incidence of zoonotic Staphylococcus pseudintermedius and Microsporum canis infections is rapidly growing worldwide in the context of an increasing frequency of close contact between animals and humans, presenting challenges in both human and veterinary medicine. Moreover, the development of microbial resistance and emergence of recalcitrant biofilms, accompanied by the insufficiency of new antimicrobial agents, have become major obstacles in treating superficial skin infections caused by various microbes including S. pseudintermedius and M. canis. Over recent years, the prospects of antimicrobial peptides as emerging antimicrobials to combat microbial infections have been demonstrated. In our study, two novel short-chain peptides, namely, allomyrinasin and andricin B, produced by Allomyrina dichotoma and Andrias davidianus, were revealed to exhibit potent antimicrobial efficacy against clinical isolates of S. pseudintermedius and M. canis with remarkable and rapid fungicidal and bactericidal effects, while allomyrinasin exhibited inhibition of biofilm formation and eradication of mature biofilm. These peptides displayed synergistic activity when combined with amoxicillin and terbinafine against S. pseudintermedius and M. canis. Cytoplasmic leakage via cytomembrane permeabilization serves as a mechanism of action. Extremely low hemolytic activity and serum stability in vitro, as well as superior anti-infective efficacy in reducing bacterial counts and relieving the inflammatory response in vivo, were detected. The potent antibacterial, antifungal, and anti-inflammatory activities of allomyrinasin and andricin B might indicate promising anti-infective alternatives for the treatment of S. pseudintermedius and M. canis infections in the context of human and veterinary medicine.

Citrullination Alters the Antibacterial and Anti-Inflammatory Functions of the Host Defense Peptide Canine Cathelicidin K9CATH In Vitro.

K9CATH is the sole cathelicidin in canines (dogs) and exhibits broad antimicrobial activity against both Gram-positive and Gram-negative bacteria. K9CATH also modulates inflammatory responses and binds to LPS. These activities depend on the secondary structure and a net-positive charge of the peptide. Peptidylarginine deiminases (PAD) convert cationic peptidyl arginine to neutral citrulline. Thus, we hypothesized that citrullination is a biologically relevant modification of the peptide that would reduce the antibacterial and LPS-binding activities of K9CATH. Recombinant PAD2 and PAD4 citrullinated K9CATH to various extents and circular dichroism spectroscopy revealed that both native and citrullinated K9CATH exhibited similar α-helical secondary structures. Notably, citrullination of K9CATH reduced its bactericidal activity, abolished its ability to permeabilize the membrane of Gram-negative bacteria and reduced the hemolytic capacity. Electron microscopy showed that citrullinated K9CATH did not cause any morphological changes of Gram-negative bacteria, whereas the native peptide caused clear alterations of membrane integrity, concordant with a rapid bactericidal effect. Finally, citrullination of K9CATH impaired its capacity to inhibit LPS-mediated release of proinflammatory molecules from mouse and canine macrophages. In conclusion, citrullination attenuates the antibacterial and the LPS-binding properties of K9CATH, demonstrating the importance of a net positive charge for antibacterial lysis of bacteria and LPS-binding effects and suggests that citrullination is a means to regulate cathelicidin activities.