Investigation of the antibacterial activity of a short cationic peptide against multidrug-resistant Klebsiella pneumoniae and Salmonella typhimurium strains and its cytotoxicity on eukaryotic cells

New ATP-competitive inhibitors of E. coli GyrB obtained from the mapping of the hydrophobic floor at the binding site: synthesis and biological evaluation

We mapped the hydrophobic floor, an interesting subsite at the active site of DNA gyrase B (GyrB) from E. coli. We synthesized three new compounds with pendant groups targeting the hydrophobic floor and evaluated their inhibitory activities on DNA gyrase. A new benzothiazole derivative with a benzyl substituent at position 3 of the benzothiazole ring exhibited strong inhibitory activity against E. coli DNA gyrase (IC50 = 19 ± 3 nM). An exhaustive conformational study using potential energy surfaces (PESs) allowed us to map the new subsite evaluating all critical points on the surface and conformational interconversion pathways. We analyzed the molecular interactions using QTAIM calculations. Our data provide insights into the mechanism of action of these new ligands at the molecular level. Theoretical and experimental data suggest that new ligand optimization strategies should focus on strengthening interactions at the hydrophobic floor while preserving the binding mode of the main scaffold.

Antimicrobial peptide-fibrin glue mixture for treatment of methicillin-resistant Staphylococcus aureus-infected wounds

Aim: This study was conducted to investigate the effect of fibrin glue-CM11 antibacterial peptide mixture (FG-P) on the healing of infected wounds in vivo.Materials & methods: We formulated a mixture of FG-P and evaluated its antimicrobial activity in vitro against multidrug-resistant (MDR) bacteria involved in wound infection as well as its healing effect on wound infected by methicillin-resistant S. aureus (MRSA) in vivo.Results: The peptide had an MIC of 8 μg/ml against all bacteria isolates. Growth inhibition zones were evident for FG-P compared with FG. The in vivo study showed that the FG-P could be significantly effective in healing the MRSA-infected wound.Conclusion: The use of FG-P mixture is a very suitable option for treating infected wounds.

Nanoparticle-Based Strategies for Managing Biofilm Infections in Wounds: A Comprehensive Review

Chronic wounds containing opportunistic bacterial pathogens are a growing problem, as they are the primary cause of morbidity and mortality in developing and developed nations. Bacteria can adhere to almost every surface, forming architecturally complex communities called biofilms that are tolerant to an individual's immune response and traditional treatments. Wound dressings are a primary source and potential treatment avenue for biofilm infections, and research has recently focused on using nanoparticles with antimicrobial activity for infection control. This Review categorizes nanoparticle-based approaches into four main types, each leveraging unique mechanisms against biofilms. Metallic nanoparticles, such as silver and copper, show promising data due to their ability to disrupt bacterial cell membranes and induce oxidative stress, although their effectiveness can vary based on particle size and composition. Phototherapy-based nanoparticles, utilizing either photodynamic or photothermal therapy, offer targeted microbial destruction by generating reactive oxygen species or localized heat, respectively. However, their efficacy depends on the presence of light and oxygen, potentially limiting their use in deeper or more shielded biofilms. Nanoparticles designed to disrupt extracellular polymeric substances directly target the biofilm structure, enhancing the penetration and efficacy of antimicrobial agents. Lastly, nanoparticles that induce biofilm dispersion represent a novel strategy, aiming to weaken the biofilm's defense and restore susceptibility to antimicrobials. While each method has its advantages, the selection of an appropriate nanoparticle-based treatment depends on the specific requirements of the wound environment and the type of biofilm involved. The integration of these nanoparticles into wound dressings not only promises enhanced treatment outcomes but also offers a reduction in the overall use of antibiotics, aligning with the urgent need for innovative solutions in the fight against antibiotic-tolerant infections. The overarching objective of employing these diverse nanoparticle strategies is to replace antibiotics or substantially reduce their required dosages, providing promising avenues for biofilm infection management.

The Mechanism of Antimicrobial Small-Cationic Peptides from Coarse-Grained Simulations

Antimicrobial cationic peptides (AMPs) are excellent candidates for use as therapeutic antimicrobial agents. Among them, short peptides possessing sequences of 9-11 amino acids have some advantages over long-sequence peptides. However, one of the main limitations of short peptides is that their mechanism of action at the molecular level is not well-known. In this article, we report a model based on multiscale molecular dynamics simulations of short peptides interacting with vesicles containing palmitoyl-oleoyl-phosphatidylglycerol (POPG)/palmitoyl-oleoyl-phosphatidylethanolamine (POPE). Simulations using this approach have allowed us to understand the different behaviors of peptides with antimicrobial activity with respect to those that do not produce this effect. We found remarkable agreement with a series of experimental results directly supporting our model. Moreover, these results allow us to understand the mechanism of action at the molecular level of these short peptides. Our simulations suggest that mechanical inhomogeneities appear in the membrane, promoting membrane rupture when a threshold concentration of peptides adsorbed on the membrane is achieved. These results explain the high structural demand for these peptides to maintain a delicate balance between the affinity for the bilayer surface, a low peptide-peptide repulsion (in order to reach the threshold concentration), and an acceptable tendency to penetrate into the bilayer. This mechanism is different from those proposed for peptides with long amino acid sequences. Such information is very useful from the medicinal chemistry point of view for the design of new small antimicrobial peptides.

Evaluation of an antibacterial peptide-loaded amniotic membrane/silk fibroin electrospun nanofiber in wound healing

Antimicrobial peptides (AMPs) are among the compounds that have significant potential to deal with infectious skin wounds. Using wound dressings or skin scaffolds containing AMPs can be an effective way to overcome infections caused by antibiotic-resistant strains. In this study, we developed an amniotic membrane-based skin scaffold using silk fibroin to improve mechanical properties and CM11 peptide as an antimicrobial peptide. The peptide was coated on the scaffold using the soaking method. The fabricated scaffold was characterised by SEM and FTIR, and their mechanical strength, biodegradation, peptide release, and cell cytotoxicity analyses were performed. Then, their antimicrobial activity was measured against antibiotic-resistant strains of Pseudomonas aeruginosa and Staphylococcus aureus. The in vivo biocompatibility of this scaffold was evaluated by subcutaneously implanting it under the skin of the mouse and counting lymphocytes and macrophages in the implanted area. Finally, the regenerative ability of the scaffold was analyzed in the mouse full-thickness wound model by measuring the wound diameter, H&E staining, and examining the expression rate of genes involved in the wound healing process. The developed scaffolds exerted an inhibiting effect on the bacteria growth, indicating their proper antimicrobial property. In vivo biocompatibility results showed no significant count of macrophages and lymphocytes between the test and control groups. The wound closure rate was significantly higher in the wound covered with fibroin electrospun-amniotic membrane loaded with 32 μg/mL CM11, where the relative expression rates of collagen I, collagen III, TGF-β1 and TGF-β3 were higher compared with the other groups.

Anti-parasitic activity of a chimeric peptide Cecropin A (2-8)-Melittin (6-9) (CM11) against tachyzoites of Toxoplasma gondii and the BALB/c mouse model of acute toxoplasmosis

Toxoplasmosis is a zoonotic disease that infects most animals, including humans. Pyrimethamine/sulfadiazine is the standard treatment for toxoplasmosis. Although this treatment has been successful, it is often associated with side effects that cannot be tolerated. Therefore, various compounds have been proposed as alternative treatments for toxoplasmosis. Antimicrobial peptides (AMPs) act on various pathogens, from viruses to protozoa. The purpose of the present study was to evaluate the effects of CM11 on in vitro and in vivo Toxoplasma gondii infection. For in vitro experiments, VERO cells were treated with different concentrations of CM11 (1-128 μg/ml) compared to sulfadiazine (SDZ) (0.78-100 μg/ml). MTT and lactate dehydrogenase (LDH) assays evaluated the cell viability and plasma membrane integrity. Then, the inhibitory concentration (IC50) values were determined for treating tachyzoites of T. gondii before or on cells previously infected. Annexin V-FITC/propidium iodide (PI) staining was used to distinguish viable and apoptotic cells. The effect of CM11, SDZ, and a combination of CM11 and SDZ was evaluated in the BALB/c mouse model of acute toxoplasmosis. CM11 was effective on tachyzoites of T. gondii and had a time and dose-dependent manner. The results of the MTT assay showed that the CC50 values of CM11 and SDZ were estimated at 17.4 µg/ml and 62.3 µg/ml after 24-h, respectively. The inhibitory concentration (IC50) of CM11 and SDZ on infected cells was estimated at 1.9 µg/ml and 1.4 µg/ml after 24-h, respectively. The highest rate of apoptosis (early and late) in high concentrations of SDZ and CM11 was determined for tachyzoites (2.13 % and 13.88 %), non-infected VERO cells (6.1 % and 19.76 %), and infected VERO cells (7.45 % and 29.9 %), respectively. Treating infected mice with CM11 and a combination of CM11 and SDZ had increased survival time. Based on the mentioned results, it can be concluded that CM11 has a beneficial effect on tachyzoites of T. gondii in vitro. The result of the mouse model suggests that CM11, either alone or in combination with other chemotherapeutic agents, could be a potential therapeutic for toxoplasmosis. Hence, antimicrobial peptides could be applied as promising anti-toxoplasma agents for treating toxoplasmosis.

Targeted delivery of a short antimicrobial peptide (CM11) against Helicobacter pylori gastric infection using concanavalin A-coated chitosan nanoparticles

Helicobacter pylori is the cause of most cases of stomach ulcers and also causes some digestive cancers. The emergence and spread of antibiotic-resistant strains of H. pylori is one of the most important challenges in the treatment of its infections. The present study aims to develop a concanavalin A (ConA) coated chitosan (CS) nanocarrier-based drug delivery for the targeted release of peptides to the site of H. pylori infection. Accordingly, chitosan was used as an encapsulating agent for CM11 peptide delivery by applying ionotropic gelation method. Con-A was used for coating CS nanoparticles to target H. pylori. The CS NPs and ConA-CS NPs were characterized by FTIR, dynamic light scattering (DLS), and scanning electron microscopy (SEM). The MIC of CM11-loaded ConA-CS NPs against H. pylori SS1 strain was analyzed in vitro. In order to evaluate the treatment efficiency in vivo, a gastric infection model of H. pylori SS1 strain was established in mice and histopathological studies and IL-1β cytokine assay were performed. Based on the results, the size frequency for CS NPs and ConA-CS NPs was about 200 and 350 nm, respectively. The prepared CM11-loaded ConA-CS NPs exhibited antibacterial activity against H. pylori SS1 strain with a concentration of 32 µg/ml. The highest healing process was observed in synthesized CM11-loaded ConA-CS NPs treatments and a significant decrease in IL-1β was observed. Our findings highlight the potential of chitosan nanoparticles as a drug delivery vehicle in the treatment of gastric infection model of H. pylori SS1 strain.

Antimicrobial peptide-loaded decellularized placental sponge as an excellent antibacterial skin substitute against XDR clinical isolates

Post-wound infections have remained a serious threat to society and healthcare worldwide. Attempts are still being made to develop an ideal antibacterial wound dressing with high wound-healing potential and strong antibacterial activity against extensively drug-resistant bacteria (XDR). In this study, a biological-based sponge was made from decellularized human placenta (DPS) and then loaded with different concentrations (0, 16 µg/mL, 32 µg/mL, 64 µg/mL) of an antimicrobial peptide (AMP, CM11) to optimize an ideal antibacterial wound dressing. The decellularization of DPS was confirmed by histological evaluations and DNA content assay. The DPS loaded with different contents of antimicrobial peptides (AMPs) showed uniform morphology under a scanning electron microscope (SEM) and cytobiocompatibility for human adipose tissue-derived mesenchymal stem cells. Antibacterial assays indicated that the DPS/AMPs had antibacterial behavior against both standard strain and XDR Acinetobacter baumannii in a dose-dependent manner, as DPS loaded with 64 µg/mL showed the highest bacterial growth inhibition zone and elimination of bacteria under SEM than DPS alone and DPS loaded with 16 µg/mL and 32 µg/mL AMP concentrations. The subcutaneous implantation of all constructs in the animal model demonstrated no sign of acute immune system reaction and graft rejection, indicating in vivo biocompatibility of the scaffolds. Our findings suggest the DPS loaded with 64 µg/mL as an excellent antibacterial skin substitute, and now promises to proceed with pre-clinical and clinical investigations.

Molecular Docking, Anti-Biofilm & Antibacterial Activities and Therapeutic Index of mCM11 Peptide on Acinetobacter baumannii Strains

Despite the huge efforts of microbiologists, infectious diseases have yet remained one of the leading causes of death in humans, further highlighting the research priority for controlling opportunistic pathogens. Many researchers have used antibacterial peptides to solve the problem of antibiotic resistance. This research is thus conducted to investigate the antibacterial and anti-biofilm activity of a novel modified cecropin-melittin 11-peptide with improved therapeutic properties and lower side effects. After synthesis and purification of mCM11 (NH2-WRLFRRILRVL-NH2) by solid-phase synthesis and HPLC methods, respectively, the antibacterial and biofilm inhibitory activities were explored in vitro. TMHMM was used to confirm the reaction of mCM11 on the plasma membrane of the prokaryotic cells. The interaction between mCM11 on Acinetobacter baumannii strains was investigated by molecular docking using ClusPro2.0. Hemolysis and therapeutic indexes were also calculated to quantify the relative safety and adverse effects of mCM11. According to the results, mCM11 has a high inhibitory and lethal effect on A. baumannii strains due to its cationic properties and new specific sequence. Molecular docking revealed the release of a significant amount of energy when mCM11 binds to the surface of A. baumannii in an appropriate site. The findings indicated that mCM11 IC50 (4 μg/mL) lysed 2.78% of RBCs; moreover, 8 strains of Acinetobacter baumannii showed a favorable therapeutic index. The mCM11 exhibits strong antibacterial and antibiofilm activities against A. baumannii strains, suggesting its potential therapeutic role in infections caused by these strains. Similar to its impact on A. baumannii, mCM11 could be a suitable alternative to antibiotics in combat against antibiotic-resistant bacteria in the in vivo experiments.

Short Antimicrobial Peptides: Therapeutic Potential and Recent Advancements

There has been a lot of interest in antimicrobial peptides (AMPs) as potential next-generation antibiotics. They are components of the innate immune system. AMPs have broad-spectrum action and are less prone to resistance development. They show potential applications in various fields, including medicine, agriculture, and the food industry. However, despite the good activity and safety profiles, AMPs have had difficulty finding success in the clinic due to their various limitations, such as production cost, proteolytic susceptibility, and oral bioavailability. To overcome these flaws, a number of solutions have been devised, one of which is developing short antimicrobial peptides. Short antimicrobial peptides do have an advantage over longer peptides as they are more stable and do not collapse during absorption. They have generated a lot of interest because of their evolutionary success and advantageous properties, such as low molecular weight, selective targets, cell or organelles with minimal toxicity, and enormous therapeutic potential. This article provides an overview of the development of short antimicrobial peptides with an emphasis on those with ≤ 30 amino acid residues as a potential therapeutic agent to fight drug-resistant microorganisms. It also emphasizes their applications in many fields and discusses their current state in clinical trials.

The Remarkable Innate Resistance of Burkholderia bacteria to Cationic Antimicrobial Peptides: Insights into the Mechanism of AMP Resistance

Gram-negative bacteria belonging to the genus Burkholderia are remarkably resistant to broad-spectrum, cationic, antimicrobial peptides (AMPs). It has been proposed that this innate resistance is related to changes in the outer membrane lipopolysaccharide (OM LPS), including the constitutive, essential modification of outer membrane Lipid A phosphate groups with cationic 4-amino-4-deoxy-arabinose. This modification reduces the overall negative charge on the OM LPS which may change the OM structure and reduce the binding, accumulation, and permeation of cationic AMPs. Similarly, the Gram-negative pathogen Pseudomonas aeruginosa can quickly become resistant to many AMPs by multiple mechanisms, frequently, including activation of the arn operon, which leads, transiently, to the same modification of Lipid A. We recently discovered a set of synthetically evolved AMPs that do not invoke any resistance in P. aeruginosa over multiple passages and thus are apparently not inhibited by aminorabinosylation of Lipid A in P. aeruginosa. Here we test these resistance-avoiding peptides, within a set of 18 potent AMPs, against Burkholderia thailandensis. We find that none of the AMPs tested have measurable activity against B. thailandensis. Some were inactive at concentrations as high as 150 μM, despite all having sterilizing activity at ≤ 10 μM against a panel of common, human bacterial pathogens, including P. aeruginosa. We speculate that the constitutive modification of Lipid A in members of the Burkholderia genus is only part of a broader set of modifications that change the architecture of the OM to provide such remarkable levels of resistance to cationic AMPs.

Investigation of Antiparasitic Effects of Eisenia fetida Extract (Annelida, Lumbricidae) Against Toxoplasma gondii: In Vitro Study

Background:

Toxoplasmosis which is caused by Toxoplasma gondii, is a widespread parasitic disease that affects approximately one-third of the world's population. Due to the significant side effects of anti-Toxoplasma drugs, it is necessary to acquire new drugs with low toxicity, high activity, cheaper and more effective.

Objective:

Earthworm has long been used as a therapeutic source of medicine in China and other parts of the Far East. Therefore, the purpose of the present study was to investigate of antiparasitic effects of Eisenia fetida extract against T. gondii in the Vero cell line.

Materials and Methods:

The effects of the extract on the parasite, Vero cell, and the parasitized cells were estimated by MTT assay in vitro. Apoptosis was also measured by flow cytometer in three groups of extract-treated parasites, extract-treated Vero cells, and extract-treated parasitic Vero cells, respectively.

Results:

The inhibitory effect of E. fetida extract and sulfadiazine was more than 85% and 65% on the parasite, respectively. Intracellular multiplication of the parasite in Vero cells during the 3 hours test showed a significant decrease compared to the 1 hour test (p<0.05). Flow cytometric analysis showed that with increasing concentration of E. fetida, apoptosis increased significantly (p<0.05).

Conclusion:

The results showed that E. fetida extract in vitro could have a significant antiparasitic effect against T. gondii.

Hyaluronic acid-coated chitosan nanoparticles as targeted-carrier of tamoxifen against MCF7 and TMX-resistant MCF7 cells

Tamoxifen (TMX) is used to treat hormone-receptor-positive breast cancers at early stages. This research aimed to assess the potential of NPs in targeted delivery of TMX against MCF7 and TMX-resistant MCF7 breast cancer cell lines. For this purpose, a targeted delivery system including chitosan NPs coated with hyaluronic acid (HA-CS NPs) was created and examined in vitro. Chitosan NPs were first fabricated and loaded with TMX using the ionic-gelation method to prepare a drug-delivery system. Then, TMX-loaded CS NPs were coated by crosslinking the amino groups of chitosan to the carboxylic group of hyaluronic acid. The developed TMX delivery system was then optimized and characterized for particle fabrication, drug release, and targeting against cancer cells. The HA-CS particle size was 210 nm and its zeta potential was +25 mv. The encapsulation efficiency of TMX in NPs was 55%. TMX released from the NPs in acidic pH (5-6) was higher than the physiological pH (7.4). The cytotoxic effect of TMX-loaded HA-CS NPs on MCF7 and TMX-resistant MCF7 cells was significantly higher than TMX-loaded CS NPs and free drug. The findings confirmed the significant suppressive impact of TMX-loaded HA-CS NPs on MCF7 and TMX-resistant MCF7 cancer cells compared to the TMX-loaded CS NPs and free TMX. Graphical abstract.

The antimicrobial effect of quorum sensing autoinducers of Pseudomonas aeruginosa, C12-HSL and C4-HSL, against MDR Staphylococcus aureus isolates

In the current study, we investigated the antibacterial activity of main quorum sensing autoinducers of Pseudomonas aeruginosa, C12-HSL and C4-HSL, against MDR Staphylococcus aureus isolates and their synergistic effects with some common antibiotics. Forty clinical isolates of S. aureus were collected and their antibiotic susceptibility pattern was evaluated. Then, 10 resistant isolates were selected for further studies. In the following, the antibacterial activity of quorum sensing C12-HSL and C4-HSL inducers of P. aeruginosa was evaluated against selected isolates based on the microdilution method and Time Killing assay as well as their synergistic activity with selected antibiotics. The ability of inductors to hemolysis and their cytotoxicity on CHO and HeLa cell lines was also assessed. For the assessment of antibacterial activity, Acinetobacter baumannii was used as negative control. The results demonstrated that C12 and C4 have antibacterial activity against MDR S. aureus isolates but had no effect on A. baumannii. Time Killing test showed that at 2X MIC concentration, the maximum inhibition (100%) is observed after 120 min for C12 and 240 min for C4. The IC₅₀ of inducers was about 512 μg/ml. In addition, no synergistic effects were observed.

Supplementation of zebrafish (Danio rerio) diet using a short antimicrobial peptide: Evaluation of growth performance, immunomodulatory function, antioxidant activity, and disease resistance

Short-chain bioactive peptides are new and promising antimicrobial, immune moderating, and antioxidant agents. Therefore, the present study was conducted to evaluate in vitro antibacterial activity of CM11, a short antimicrobial peptide (AMP), against Streptococcus iniae and Yersinia ruckeri as fish pathogenic bacteria using standard disk diffusion and microdilution assays. In addition, in vivo effects of CM11 on fish growth, immunity, antioxidant activity, and disease resistance were evaluated using zebrafish (Danio rerio) as an animal model. For in vivo study, based on in vitro susceptibility results, four diets were designed to include zero (as control), 10, 20, and 50 μg of CM11 per g diet referred to as control, P1, P2, and P3 treatments, respectively. After eight weeks of dietary trial, fish were challenged with Streptococcus iniae, and the survival rate was calculated for a period of two weeks. Results showed that CM11 effectively inhibited the growth of S. iniae and Y. ruckeri on agar plates at a concentration of eight μg/ml. Minimum inhibitory and minimum bactericidal concentrations of CM11 were measured at 8 and 32 μg/ml for S. iniae and 16 and 64 μg/ml Y. ruckeri, respectively. In vivo results showed no noticeable effects on fish growth parameters, however, feed conversion ratio (FCR) was found lower in P3 and P2 compared to control (P < 0.05). Immunological and antioxidant responses were found strongly affected by CM11 in all treatment groups in which the highest values were found in the P3 treated group. Key immune and antioxidant genes were up-regulated particularly in fish receiving the highest level of CM11 (P3). Fish receiving the CM11 peptide showed better survival when challenged with S. iniae. These findings suggest the potential of CM11 for use in aquaculture as an antibacterial and immunostimulant agent.

Fabrication and characterization of an antibacterial chitosan/silk fibroin electrospun nanofiber loaded with a cationic peptide for wound-dressing application

Wound infections are still problematic in many cases and demand new alternatives for current treatment strategies. In recent years, biomaterials-based wound dressings have received much attention due to their potentials and many studies have been performed based on them. Accordingly, in this study, we fabricated and optimized an antibacterial chitosan/silk fibroin (CS/SF) electrospun nanofiber bilayer containing different concentrations of a cationic antimicrobial peptide (AMP) for wound dressing applications. The fabricated CS/SF nanofiber was fully characterized and compared to the electrospun silk fibroin and electrospun chitosan alone in vitro. Then, the release rate of different concentrations of peptide (16, 32, and 64 µg/ml) from peptide-loaded CS/SF nanofiber was investigated. Finally, based on cytotoxic activity, the antibacterial activity of scaffolds containing 16 and 32 µg/ml of the peptide was evaluated against standard and multi-drug resistant strains of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa isolated from burn patients. The peptide-loaded CS/SF nanofiber displayed appropriate mechanical properties, high water uptake, suitable biodegradation rate, a controlled release without cytotoxicity on Hu02 human foreskin fibroblast cells at the 16 and 32 µg/ml concentrations of peptide. The optimized CS/SF containing 32 μg/ml peptide showed strong antibacterial activity against all experimental strains from standard to resistance. The results showed that the fabricated antimicrobial nanofiber has the potential to be applied as a wound dressing for infected wound healing, although further studies are needed in vivo.

Evaluation of curcumin and CM11 peptide alone and in combination against amastigote form of Iranian strain of L. major (MRHO/IR75/ER) in vitro

Curcumin (diferuloylmethane) is the main phytochemical of Curcuma longa Linn, an extract of the rhizome turmeric. For thousands of years, turmeric among other natural products has been used as a dietary spice and as a medicinal plant in Asian countries. The present study reports the leishmanicidal activity of curcumin in different concentrations (10 μM, 20 μM, 40 μM). It is also showing the effect of CM11 peptide (8 μM) alone and in combination with curcumin (10 and 20 μM) as a leishmanicidal drug. The experiments were performed with the amastigote form of Leishmania major (MRHO/IR/75/ER) in vitro and the leishmanicidal activity was analyzed after 12 and 24 h of incubation by Giemsa and DAPI staining. Further investigation was done by using semi-quantitative PCR with new designed common primer pair derived from an 18S rRNA gene belonging to the L. major and mouse, which amplified the above-mentioned gene segments simultaneously with different PCR product size. Our findings showed that curcumin had leishmanicidal activity in a dose and time-dependent manner and its lowest effective dose was at concentrations of 40 μM afetr12 h and 10 μM after 24 h. The IC₅₀ value of curcumin against amastigote forms of L. major was 21.12 μM and 11.77 μM after 12 and 24 h, respectively. Treatment of amastigote form with CM11 (8 μM) alone and in combination with curcumin (10 μM and 20 μM) showed less leishmanicidal activity. Interestingly, CM11 in combination with curcumin (10 μM and 20 μM) had even less leishmanicidal effect compared to curcumin alone in the same concentrations (10 μM and 20 μM). The semi-quantitative PCR analysis confirmed the data achieved by Giemsa and DAPI staining and showed that curcumin reduced the PCR product derived from amastigote form in concentration and time-dependent manner compared to the genome of the host cells.

Komodo-dragon cathelicidin-inspired peptides are antibacterial against carbapenem-resistant Klebsiella pneumoniae

Introduction.The rise of carbapenem-resistant enterobacteriaceae (CRE) is a growing crisis that requires development of novel therapeutics.

Hypothesis.To this end, cationic antimicrobial peptides (CAMPs) represent a possible source of new potential therapeutics to treat difficult pathogens such as carbapenem-resistantKlebsiella pneumoniae(CRKP), which has gained resistance to many if not all currently approved antibiotics, making treatment difficult.

Aim.To examine the anti-CRKP antimicrobial activity of the predicted cathelicidins derived fromVaranus komodoensis(Komodo dragon) as well as synthetic antimicrobial peptides that we created.

Methodology.We determined the minimum inhibitory concentrations of the peptides against CRKP. We also characterized the abilities of these peptides to disrupt the hyperpolarization of the bacterial membrane as well as their ability to form pores in the membrane.

Results.We did not observe significant anti-CRKP activity for the predicted native Komodo cathelicidin peptides. We found that the novel peptides DRGN-6,-7 and -8 displayed significant antimicrobial activity against CRKP with MICs of 4–8 µg ml−1. DRGN-6 peptide was the most effective peptide against CRKP. Unfortunately, these peptides showed higher than desired levels of hemolysis, althoughin vivotesting in the waxwormGalleria mellonellashowed no mortality associated with treatment by the peptide; however, CRKP-infected waxworms treated with peptide did not show an improvement in survival.

Conclusion.Given the challenges of treating CRKP, identification of peptides with activity against it represents a promising avenue for further research. Given DRGN-6′s similar level of activity to colistin, DRGN-6 is a promising template for the development of novel antimicrobial peptide-based therapeutics.

Antimicrobial efficacy of Cecropin A (1-7)- Melittin and Lactoferricin (17-30) against multi-drug resistant Salmonella Enteritidis

The present study evaluated intracellular antibacterial efficacy of two short-chain cationic antimicrobial peptides (AMPs) namely, Cecropin A (1-7)-Melittin and lactoferricin (17-30) against three field strains of multi-drug resistant Salmonella Enteritidis. Initially, antimicrobial ability of both the AMPs was evaluated for their minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against multi-drug resistant S. Enteritidis strains. Besides, the AMPs were evaluated for its in vitro stability (high-end temperatures, proteases, physiological concentrations of cationic salts and pH) and safety (haemolytic assay in sheep erythrocytes; cytotoxicity assay in murine macrophage RAW 264.7 cell line and human epithelioma HEp-2 cell line and beneficial gut lactobacilli). Later, a time-kill assay was performed to assess the intracellular antibacterial activity of Cecropin A (1-7)-Melittin and lactoferricin (17-30) against multi-drug resistant S. Enteritidis in RAW 264.7 and HEp-2 cells. The observed MBC values of Cecropin A (1-7)-Melittin and lactoferricin (17-30) against multi-drug resistant S. Enteritidis (128 μM; 256 μM) were generally twice or four-fold greater than the MIC values (64 μM). Further, both the AMPs were found variably stable after exposure at high-end temperatures (70 °C and 90 °C), protease treatment (trypsin, proteinase K, lysozyme), higher concentration of physiological salts (150 mM NaCl and 2 mM MgCl₂) and hydrogen ion concentrations (pH 4.0 to 8.0). Both the AMPs were found non-haemolytic on sheep erythrocytes, revealed minimal cytotoxicity in RAW 264.7 and HEp-2 cells, and was tested safe against beneficial gut lactobacilli (L. acidophilus and L. rhamnosus). Intracellular bacteriostatic effect with both cationic AMPs against multi-drug resistant S. Enteritidis was evident in RAW 264.7 cells; however, in both the cell lines, the significant bactericidal effect was not observed (P > 0.05) with both cationic AMPs understudy against multi-drug resistant S. Enteritidis. Based on the results of the present study, both the cationic AMPs understudy may not be useful for the intracellular elimination of multi-drug resistant S. Enteritidis; hence, further studies such as conjugation of these AMPs with either cell-penetrating peptides (CPP) and/or nanoparticles (NPs) are warranted.

Heterologous expression of biologically active Mambalgin-1 peptide as a new potential anticancer, using a PVX-based viral vector in Nicotiana benthamiana

Mambalgin-1 is a peptide that acts as a potent analgesic through inhibiting acid-sensing ion channels (ASIC) in nerve cells. Research has shown that ASIC channels are involved in the proliferation and growth of cancer cells; therefore, Mambalgin-1 can be a potential anti-cancer by inhibiting these channels. In the present study, the Nicotiana benthamiana codon optimized Mambalgin-1 gene was synthesized and cloned in PVX (potato virus X) viral vector. The two cultures of Agrobacterium containing Mambalgin-1 and P19 silencing suppressor genes were co-agroinfiltrated into N. benthamiana leaves. Five days post infiltration, the production of recombinant Mambalgin-1 was determined by western blotting. For biological activity, MTT (3(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide) was analyzed for the cytotoxicity recombinant Mambalgin-1 from the transformed plants on nervous (SH-SY5Y) and breast (MCF7) cancer cells. The results showed that the plants expressing open reading frame of Mambalgin-1 showed recombinant 7.4 kDa proteins in the entire plant extract. In the MTT test, it was found that Mambalgin-1 had cytotoxic effects on SH-SY5Y cancer cells, yet no effects on MCF7 cancer cells were observed. According to the results, the expression of the biologically active recombinant Mambalgin-1 in the transformed plant leaves was confirmed and Mambalgin-1 can also have anti-cancer (inhibition of ASIC channels) potential along with its already known analgesic effect.

In vitro toxicity evaluation of short cationic antimicrobial peptide (CM11) on Blastocystis sp

Blastocystis infection accounts for one of the causes of gastrointestinal problems with the prevalence rate of 3-100% worldwide. There is a wide range of drugs examined for the treatment of infected patients, among them metronidazole (MTZ) has been introduced as one of the efficient drugs. Besides to the suitable clinical effects, the administration of MTZ has some reported side-effects which emphasize on the identification of putative alternates. To this end, we aimed to evaluate the cytotoxicity effect of a newly-introduced synthetic antimicrobial peptide (AMP) named CM11 on in vitro cultured Blastocystis. Our results exhibited that CM11 treatment affected the viability of parasites in two cultural conditions including culturing alone and in co-culture with the Caco-2 cell line. The time- and dose-dependent effect of CM11 was consistent with the effect of MTZ which was used as control positive. The highest toxicity effect of CM11 was observed at the concentration of 24 μg/ml, leading to 28.7% and 25% viable parasites after 24 h and 48 h incubation times, respectively. Interestingly, the disruption of the Blastocystis cell membrane could be observed in the treated parasites. Therefore, CM11 can be suggested as a potential treatment for Blastocystis-infected patients after further in vitro and in vivo assessments.

Assessment of Susceptibility to Five Common Antibiotics and Their Resistance Pattern in Clinical Enterococcus Isolates

Background & Objective:

Enterococcus Species are the common cause of nosocomial infections, which are highly resistant to different antibiotics. Therefore, determination of their antibiotic susceptibility patterns and simultaneous resistance to antibiotics is important for better treatment strategies.

Methods:

400 clinical Enterococcus isolates were collected from different hospitals in Tehran, Iran. Standard phenotypic-biochemical tests and PCR were used to identify the Enterococcus species. The antimicrobial susceptibility patterns and simultaneous resistance to selected antibiotics were determined by disk diffusion method according to the CLSI guidelines. All data analysis was performed using Python packages Scipy and Stats models.

Results:

According to the biochemical and PCR analyses, among 400 Enterococcus species, 72% of samples were Enterococcus faecalis, 10.75% Enterococcus faecium, and 17.25% other Enterococcus species. The results determined antimicrobial resistances of these strains against gentamicin, vancomycin, fosfomycin trometamol, teicoplanin, and quinupristin/dalfopristin. Results confirmed a significant correlation between resistance to vancomycin and resistance to teicoplanin. This correlation remains significant when including only E. faecium or E. faecalis species. We also found a negative correlation between resistance to teicoplanin and quinupristin/dalfopristin. Additionally, Quinupristin/dalfopristin was the least effective antibiotic while vancomycin and teicoplanin were the most effective ones.

Conclusion:

Based on the results and association between simultaneous resistance to some antibiotics such as vancomycin and teicoplanin, in the case of antibiotic resistance, the choice of a second antibiotic can be very important which can lead to good or bad effects.

Clonal diversity of Haemophilus influenzae carriage isolated from under the age of 6 years children

Objectives

Pharyngeal carriers such as H. influenzae seem to constitute the only reservoir and probably the only transmission vehicle of the invasive disease. The aims of this study were to estimate the prevalence of H. influenzae carriage, to characterize antibiotic susceptibility, and to explore genetic diversity of H. influenzae isolates. Sampling was carried out as nasopharynx swabs among children less than 6 years old volunteers. After traditional biochemical tests, isolates were confirmed by targeting omp6 sequence. Following the susceptibility tests, genomic diversity of strains was analyzed by Pulsed-Field Gel Electrophoresis procedure.

Results

Out of 328 nasopharynx swabs, 73 strains were identified as H. influenzae. Among H. influenzae isolates, resistance to chloramphenicol (42%) and ampicillin (43%) was observed. Levofloxacin is the most effective antibiotic and the least effect belonged to tetracycline. By genomic analysis of selected H. influenza, 28 PFGE patterns were achieved among which 11 patterns included at least 2 strains. All strains clustered into 25 different clones. The dendrogram analysis of the isolated H. influenzae strains showed that some of these strains had a clonal relationship and common genetic origin. According to our results, antibiotic resistance didn’t show any significant correlation with the clonality of strains.

Anti-amoebic activity of a cecropin-melittin hybrid peptide (CM11) against trophozoites of Entamoeba histolytica

Entamoeba histolytica is an intestinal parasite that is located in the lumen of the human intestine and can attack the epithelium. Antimicrobial peptides (AMPs) are effective against the wide range of microorganisms, such as bacteria, fungi, viruses, yeasts, and protozoa. The CM11 is a chimeric peptide that is derived from bee venom and butterfly compounds. In this study, the cytotoxic effect of CM11 on Human colonic carcinoma (Caco‑2) cells and E. histolytica were assayed in various concentrations of peptide and metronidazole. The MTT results showed that the highest percentage of cytotoxicity on Caco‑2 cells was in 24 μg/ml of CM11 peptide at 24 h and 48 h, which was 49.8%, and 44.3%, respectively. In the metronidazole group, the highest cytotoxicity with 40 μg/ml concentration was observed after 24 h and 48 h, with 43.5%, and 42.1%, respectively. The highest rate of apoptosis induced by CM11 on Caco‑2 was 53.9% and 51.4% after 24 h and 48 h, respectively; however, these rates were 19.1% and 33.4% in the metronidazole group. The effect of peptide and metronidazole on E. histolytica at 24 h and 48 h showed that at the highest concentration of CM11 peptide (24 μg/ml) the cytotoxic effect was 93.7% and 94.9% and for metronidazole (40 μg/ml) was 65.5% and 74.3%, respectively. In coculture, 63.5% and 57.7% of parasites were killed in the highest concentration of CM11 and metronidazole, respectively. The results of this study revealed that CM11 peptide has a high toxicity on E. histolytica, and the use of antimicrobial peptides in the future can be considered as anti-amoebic compounds.

Design and synthesis of new N-terminal fatty acid modified-antimicrobial peptide analogues with potent in vitro biological activity

Developing novel antimicrobial agents is a top priority in fighting against bacterial resistance. Thus, a series of new monomer and dimer peptides were designed and synthesized by conjugating fatty acids at the N-terminus of partial d-amino acid substitution analogues of anoplin and dimerization. The new peptides exhibited more efficient killing of gram-negative and gram-positive bacteria, including methicillin-resistant Staphylococcus aureus compared with the parent peptide anoplin, and the dimer peptides were superior to the monomer peptides. It was important that the new peptides displayed low impact on bacterial resistance development. In addition, the antimicrobial activities were not significantly influenced by a physiological salt environment. They also presented high stability in the presence of protease or serum. Almost all of the new peptides had better selectivity towards anionic bacterial membranes over zwitterionic mammalian cell membranes. Moreover, the new peptides displayed synergistic or additive effects when used together with the antibiotics rifampicin and polymyxin B. These results showed that the new peptides could also prevent the formation of bacterial biofilms. Furthermore, outer/inner membrane permeabilization and cytoplasmic membrane depolarization experiments revealed that the new peptides had strong membrane permeabilization and depolarization. Confocal laser scanning microscopy, flow cytometry analysis and scanning electron microscopy further demonstrated that the new peptides could damage the integrity of the bacterial membrane. Finally, a DNA-binding affinity assay showed that the new peptides could bind to bacterial DNA. In summary, the conjugation of fatty acids at the N-terminus of peptides and dimerization are promising strategies for obtaining potent antimicrobial agents.

Sarconesin II, a New Antimicrobial Peptide Isolated from Sarconesiopsis magellanica Excretions and Secretions

Antibiotic resistance is at dangerous levels and increasing worldwide. The search for new antimicrobial drugs to counteract this problem is a priority for health institutions and organizations, both globally and in individual countries. Sarconesiopsis magellanica blowfly larval excretions and secretions (ES) are an important source for isolating antimicrobial peptides (AMPs). This study aims to identify and characterize a new S. magellanica AMP. RP-HPLC was used to fractionate ES, using C18 columns, and their antimicrobial activity was evaluated. The peptide sequence of the fraction collected at 43.7 min was determined by mass spectrometry (MS). Fluorescence and electronic microscopy were used to evaluate the mechanism of action. Toxicity was tested on HeLa cells and human erythrocytes; physicochemical properties were evaluated. The molecule in the ES was characterized as sarconesin II and it showed activity against Gram-negative (Escherichia coli MG1655, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa PA14) and Gram-positive (Staphylococcus aureus ATCC 29213, Micrococcus luteus A270) bacteria. The lowest minimum inhibitory concentration obtained was 1.9 μM for M. luteus A270; the AMP had no toxicity in any cells tested here and its action in bacterial membrane and DNA was confirmed. Sarconesin II was documented as a conserved domain of the ATP synthase protein belonging to the Fli-1 superfamily. The data reported here indicated that peptides could be alternative therapeutic candidates for use in infections against Gram-negative and Gram-positive bacteria and eventually as a new resource of compounds for combating multidrug-resistant bacteria.

Effects of slit divergent ultrasound and enzymatic treatment on the structure and antioxidant activity of arrowhead protein

The arrowhead has attracted great research interest for their potential applications in pharmacy, food and biomedical areas. However, no information is reported about the nature and structure of the arrowhead protein (AP). Herein, effects of slit divergent ultrasound (28, 33, 40 KHz frequencies at 30-50 °C) and enzymatic (pepsin, trypsin, and alcalase) treatment on structure of AP were studied. In addition, changes in antioxidant activity of AP treated with ultrasound and enzymes were measured by chemical and cellular-based assays. The results showed that ultrasound treatment had considerable impact on the structure of AP and increased the susceptibility of AP to pepsin, trypsin and alcalase proteolysis. The changes in UV-Vis spectra, free sulfhydryl (SH) and disulfide bonds (SS) groups indicated that the structure of AP unfolded after ultrasound treatment. Besides, intrinsic fluorescence intensity of AP was increased by ultrasound treatment and then decreased after following enzymatic treatment. The circular dichroism (CD) analysis showed that ultrasound and enzymatic treatment decreased α-helix, β-turn of content of AP. However, the β-sheet and random coil content of AP increased. Interestingly, the AP after ultrasound and enzymatic treatment showed significant higher anti-oxidative activity in RAW 264.7 cells (p < 0.05) in comparison with control. In conclusion, the slit divergent ultrasonic provides a powerful endorsement for increasing the proteolysis of AP. Moreover, the improvement of the antioxidant activity of AP enzymatic hydrolysates provides a foundation of developing new type of plant-derived antioxidant peptides application.

Investigation of the antimicrobial activity of a short cationic peptide against promastigote and amastigote forms of Leishmania major (MHRO/IR/75/ER): An in vitro study

Cutaneous leishmaniasis is one of the most endemic global health problems in many countries all around the world. Pentavalent antimonial drugs constitute the first line of leishmaniasis treatment; however, resistance to these drugs is a serious problem. Therefore, new therapies with new modes of action are urgently needed. In the current study, we examined antimicrobial activity of CM11 hybrid peptide (WKLFKKILKVL-NH2) against promastigote and amastigote forms of L. major (MHRO/IR/75/ER). In vitro anti-leishmanial activity was identified against L. major by parasite viability and metabolic activity after exposure to different peptide concentration. In the presentt study, we demostrated that different concentrations of CM11 result in dose dependent growth inhibition of Leishmania promastigotes. Furthermore, we demostrated that CM11 peptide has significant anti-leishmanial activities on amastigotes. Our results demonstrated that CM11 antimicrobial peptide may provide an alternative therapeutic approach for L. major treatment.

Comparison of the antibacterial effects of a short cationic peptide and 1% silver bioactive glass against extensively drug-resistant bacteria, Pseudomonas aeruginosa and Acinetobacter baumannii, isolated from burn patients

We have already established that a short cationic peptide (CM11) has high antimicrobial activity against a number of bacterial pathogens. Considering the untreatable problem of burn infections caused by Pseudomonas aeruginosa and Acinetobacter baumannii, this study evaluated and compared antibacterial effects of the CM11 peptide and 1% silver-doped bioactive glass (AgBG) against extensively drug-resistant strains of these bacteria which were isolated from burn patients. Accordingly, the bacteria were isolated from burn patients and their antibiotic resistance patterns and mechanisms were fully determined. The isolated bacterial from patients were resistant to almost all commonly used antibiotics and silver treatment. The isolates acquired their resistance through inactivation of their porin, the overexpression of efflux pump, and beta-lactamase. CM11 peptide and 1% AgBG had minimum inhibitory concentration (MIC) of ≥ 16 μg ml^-1 and ≥ 4 mg ml^-1 for clinical isolates, respectively. The minimum bactericidal concentration (MBC) of peptide and 1% AgBG for resistant bacteria was ≥ 32 μg ml^-1 and ≥ 4 mg ml^-1, respectively. Among the clinical isolates, two P. aeruginosa isolates and one A. baumannii isolate were resistant to 1% AgBG disk. The CM11 peptide also showed high biocompatibility in vivo and no cytotoxicity against fibroblasts and adipose-derived mesenchymal stem cells in concentrations ≤ 64 μg ml^-1 and ≤ 32 μg ml^-1, respectively, while the safe concentration of 1% AgBG for these cells was ≤ 16 μg ml^-1. In conclusion, these findings indicated that the 1% silver is not safe and effective for treatment of such infections. The data suggest that CM11 peptide therapy is a reliable and safe strategy that can be used for the treatment of burn infections caused by antimicrobial-resistant isolates. The next stage of the study will be a multicenter clinical trial.

Antimicrobial Peptides: Features, Action, and Their Resistance Mechanisms in Bacteria

In recent years, because of increased resistance to conventional antimicrobials, many researchers have started to study the synthesis of new antibiotics to control the disease-causing effects of infectious pathogens. Antimicrobial peptides (AMPs) are among the newest antibiotics; these peptides are integral compounds in all kinds of organisms and play a significant role in microbial ecology, and critically contribute to the innate immunity of organisms by destroying invading microorganisms. Moreover, AMPs may encourage cells to produce chemokines, stimulate angiogenesis, accelerate wound healing, and influence programmed cell death in multicellular organisms. Bacteria differ in their inherent susceptibility and resistance mechanisms to these peptides when responding to the antimicrobial effects of AMPs. Generally, the development of AMP resistance mechanisms is driven by direct competition between bacterial species, and host and pathogen interactions. Several studies have shown diverse mechanisms of bacterial resistance to AMPs, for example, some bacteria produce proteases and trapping proteins; some modify cell surface charge, change membrane fluidity, and activate efflux pumps; and some species make use of biofilms and exopolymers, and develop sensing systems by selective gene expression. A closer understanding of bacterial resistance mechanisms may help in developing novel therapeutic approaches for the treatment of infections caused by pathogenic organisms that are successful in developing extensive resistance to AMPs. Based on these observations, this review discusses the properties of AMPs, their targeting mechanisms, and bacterial resistance mechanisms against AMPs.

The effect of ethanolic extract of Thymus kotschyanus on cancer cell growth in vitro and depression-like behavior in the mouse

Cancer and depression are known as two of the most debilitating disease and disorder increasing evidence suggest an urgent need for new therapeutic agents with lower toxicity and high efficacy. Some Thyme species extracts have remarkably been shown to positively affect depression and cancer cells. In the present study, we investigated the effect of Thymus kotschyanus on depression and cancer cells. To this end, in experiment 1, NMRI mice were treated orally with the ethanolic extract of T. kotschyanus (50, 150 and 250 mg/ml) for seven days and then depression-like behavior was measured by Forced Swim Test (FST) and Tail Suspension Test (TST). In experiment 2, the pharmacological effect of the extract on the lung (A549) and cervical (Hela) cancer cell lines was also evaluated by MTT (3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide) in various concentration_(10, 5, 2.5, 1.25, 0.63, 0.31, 0.15 and 0.08 mg/ml). The results indicated that T. kotschyanus extract treatment (150 and 250 mg/kg) decreased depression-like behavior in the FST and TST tests in adult mice. Moreover, the treatment inhibited cancer cell growth and viability in a dose and time-dependent manner. Collectively these findings suggest that T. kotschyanus have antidepressant and anticancer effects.

Characterization of pharmacological properties of isolated single-stranded DNA aptamers against angiotensin II

Nucleic acid aptamers can be served as drugs, carriers and diagnostic probes in living systems. Before recruiting aptamers, their pharmacological characteristics should be determined. Here we intended to investigate four important properties of isolated ssDNA anti-angiotensin II aptamers (FLC112 and FLC125) including hemolytic activity, cytotoxicity, immunogenicity and serum stability through in vitro and in vivo models. The hemolytic effect and cytotoxicity potential of aptamers were measured through hemolysis test and MTT assay respectively. In the following test, the humoral immune responses to aptamers in BALB/c mice were assessed. The human serum stability of aptamers was also determined using real-time PCR (qPCR). The results of this study revealed that the FLC112 aptamer with its unique structure had slightly higher cytotoxicity and hemolysis effect (9.14% and 0.1 ± 0.037% respectively) relative to FLC125 (8.07% and 0.08 ± 0.045% respectively) at the highest concentration (5 μM). FLC112 showed ignorable immune response in mice and barely higher than FLC125. Serum stability test confirmed that FLC112 with 12 h had more nuclease stability than FLC125 with 8 h. Aptamer molecule analysis revealed that the structure, sequense composition and motifs are the determinative parameters in aptamer pharmacological properties.

Self-assembling lipopeptides with a potent activity against Gram-positive bacteria, including multidrug resistant strains

Aim: To explore the potential of de novo designed cyclic lipopeptides and its linear counterparts as antibacterial agents. Materials & methods: The lipopeptides were synthesized via solid-phase peptide synthesis and the cyclization was achieved by using succinic acid linker. The antimicrobial activities of the lipopeptides were evaluated in vitro against a variety selection of Gram-negative and Gram-positive bacteria including clinical isolates of multidrug-resistant strains. Results: The synthesized lipopeptides were able to self-assemble into nanoparticles in an aqueous environment, with three exhibiting potent antibacterial activity against Gram-positive bacteria, including clinically relevant multidrug-resistant bacteria. Conclusion: The lead compounds have the potential to be developed as new antibacterials that are effective against Gram-positive bacteria, including multidrug-resistant isolates.

Analysis of Healing Effect of Alginate Sulfate Hydrogel Dressing Containing Antimicrobial Peptide on Wound Infection Caused by Methicillin-Resistant Staphylococcus aureus

BACKGROUND

Wound infections caused by methicillin-resistant Staphylococcus aureus are a health problem worldwide; therefore, it is necessary to develop new antimicrobial compounds. Considering broad-spectrum antimicrobial activity and low probability of drug resistance to peptides, applications these peptides are being studied extensively.

OBJECTIVES

In this study, to control drug release over time, an alginate sulfate-based hydrogel impregnated with the CM11 peptide as the antimicrobial agent was developed, and its healing effects were tested on skin infections caused by methicillin-resistant S. aureus strains in a mouse model.

MATERIALS AND METHODS

Minimum inhibitory and minimum bactericidal concentrations of the CM11 peptide and alginate hydrogel in combination with the peptide were determined. Forty mice were divided into 4 groups: 1 group as a negative control (without treatment; however, 5 mice received hydrogel dressing without peptide), 1 group as a positive control (2% mupirocin treatment), and 2 groups as test groups. To establish skin infection, 200 μL of bacterial suspension with 3 × 10(8) CFU/mL concentration was subcutaneously injected in the scapular region of the mice. On the basis of the in vitro minimal bactericidal concentration of the alginate hydrogel containing peptide for 15 clinical isolates, hydrogel containing 128 mg/L of peptide was used for wound dressing over an 8-day period.

RESULTS

The highest and lowest numbers of wounds were observed on day 2 in the negative and positive control groups, respectively. During the 8-day period, the positive control and hydrogel containing peptide treatment groups showed similar levels of wound healing.

CONCLUSIONS

This study showed that compared to standard drug treatment, treatment with hydrogel containing peptide had substantial antibacterial effects on S. aureus wound infections in mice.

High-level expression and characterization of bioactive human truncated variant of hepatocyte growth factor in Escherichia coli

Hepatocyte growth factor (HGF) is an effective anti-fibrotic factor because of its bioactivity in inhibiting fibrosis-related proteins in the development of hepatic fibrosis. However, high-level production of bioactive mature form HGF is difficult because of its complex structure. Here, we report a non-fusion protein expression system to obtain truncated variant of N-terminal hairpin and first kringle domains of HGF (tvNK1) in Escherichia coli to determine its anti-fibrotic effects on hepatic stellate cells (HSCs). Under the selected conditions of cultivation and isopropyl-β-D-1-thiogalactopyranoside induction, the expression level of tvNK1 accounted for approximately 65 % of the total cellular protein and 50 % of fusion protein in the supernatant of whole cell lysates. The recombinant protein could be purified in one step with Ni(2+)-affinity chromatograph. Finally, about 65 mg recombinant tvNK1 was obtained from 1 l fermentation culture with no <95 % purity. In vitro, the final purified tvNK1 was shown to inhibit the proliferation of HSCs and decrease the mRNA and protein expression levels of fibrosis-related COL1A1 and α-smooth muscle actin genes.