Class Of Antimicrobial Peptides Research Articles

Secretory Expression and Application of Antilipopolysaccharide Factor 3 in Chlamydomonas reinhardtii.

Anti-lipopolysaccharide factor is a class of antimicrobial peptides with lipopolysaccharide-binding structural domains, which has a broad antimicrobial spectrum, high antimicrobial activities, and broad application prospects in terms of the aquaculture industry. However, the low yield of natural antimicrobial peptides and their poor expression activity in bacteria and yeast have hindered their exploration and utilization. Therefore, in this study, the extracellular expression system of Chlamydomonas reinhardtii, by fusing the target gene with the signal peptide, was used to express anti-lipopolysaccharide factor 3 (ALFPm3) from Penaeus monodon in order to obtain highly active ALFPm3. Transgenic C. reinhardtii T-JiA2, T-JiA3, T-JiA5, and T-JiA6, were verified using DNA-PCR, RT-PCR, and immunoblot. Additionally, the IBP1-ALFPm3 fusion protein could be detected not only within the cells but also in the culture supernatant. Moreover, the extracellular secretion containing ALFPm3 was collected from algal cultures, and then its bacterial inhibitory activity was analyzed. The results showed that the extracts from T-JiA3 had an inhibition rate of 97% against four common aquaculture pathogenic bacteria, including Vibrio harveyi, Vibrio anguillarum, Vibrio alginolyticus, and Vibrio parahaemolyticus. The highest inhibition rate of 116.18% was observed in the test against V. anguillarum. Finally, the minimum inhibition concentration (MIC) of the extracts from T-JiA3 to V. harveyi, V. anguillarum, V. alginolyticus, and V. parahaemolyticus were 0.11 μg/μL, 0.088 μg/μL, 0.11 μg/μL, and 0.011 μg/μL, respectively. This study supports the foundation of the expression of highly active anti-lipopolysaccharide factors using the extracellular expression system in C. reinhardtii, providing new ideas for the expression of highly active antimicrobial peptides.

Interactions of polymyxin B1 with the gram-negative inner membrane: A simulation study.

The rise of drug resistant Gram-negative bacterial infections in recent decades has led to increased use of polymyxins, a class of antimicrobial peptides, as a ‘last resort’ treatment. In addition, the recent emergence of polymyxin-resistant strains threatens to bring about an era in which bacteria are resistant to all known antibiotics. It is thus necessary to develop new polymyxin-based antibiotics, but a lack of understanding of how polymyxins work at the molecular level may hinder such efforts. One question that remains open is how do polymyxins interact with the Gram-negative inner membrane to cause cell lysis? It has recently been suggested that polymyxins may target small quantities of the complex glycolipid lipopolysaccharide (LPS) that are present in the inner membrane prior to LPS transport to the outer membrane. In this work, we used a multiscale molecular dynamics (MD) approach including long-timescale, coarse-grained (CG) and atomistic simulations to investigate the interactions of polymyxin B1 (PMB1) with bacterial inner membrane models in the presence of small quantities of LPS. We observed that PMB1 is inserted into the inner membrane and localises at the LPS-phospholipid interface, sampling a wide range of interfacial environments. Our CG simulations also indicate that PMB1-LPS interactions are long-lived and numerous. In the presence of membrane proteins, a small number of PMB1 molecules were observed to form interactions with native inner membrane proteins, reducing the overall probability of PMB1 molecules remaining bound to LPS. Overall, this work indicates that PMB1 can target LPS molecules in the inner membrane, supporting recent hypotheses on its mode of action, while also providing new insights into the effect of membrane proteins upon PMB1-inner membrane interactions.

Combating Escherichia coli O157:H7 with Functionalized Chickpea-Derived Antimicrobial Peptides.

The rapid dissemination of antibiotic resistance accelerates the desire for new antibacterial agents. Here, a class of antimicrobial peptides (AMPs) is designed by modifying the structural parameters of a natural chickpea-derived AMP-Leg2, termed "functionalized chickpea-derived Leg2 antimicrobial peptides" (FCLAPs). Among the FCLAPs, KTA and KTR show superior antibacterial efficacy against the foodborne pathogen Escherichia coli (E. coli) O157:H7 (with MICs in the range of 2.5-4.7µmol L-1 ) and demonstrate satisfactory feasibility in alleviating E. coli O157:H7-induced intestinal infection. Additionally, the low cytotoxicity along with insusceptibility to antimicrobial resistance increases the potential of FCLAPs as appealing antimicrobials. Combining the multi-omics profiling andpeptide-membrane interaction assays, a unique dual-targeting mode of action is characterized. To specify the antibacterial mechanism, microscopical observations, membrane-related physicochemical properties studies, and mass spectrometry assays are further performed. Data indicate that KTA and KTR induce membrane damage by initially targeting the lipopolysaccharide (LPS), thus promoting the peptides to traverse the outer membrane. Subsequently, the peptides intercalate into the peptidoglycan (PGN) layer, blocking its synthesis, and causing a collapse of membrane structure. These findings altogether imply the great potential of KTA and KTR as promising antibacterial candidates in combating the growing threat of E. coli O157:H7.

A short hydrophobic peptide conjugated 3,5- disubstituted pyrazoles as antibacterial agents with DNA gyrase inhibition

Antimicrobial peptides (AMP) are found in majority of living organisms. Their mode of action is unique and different from the conventional antibiotics. Though several classes of antimicrobial peptides have been studied, their mechanism of action against microbes is not yet clearly understood, otherwise it would open up a solid background for further development of new pharmaceutical compounds. The present work describes the synthesis and evaluation of antimicrobial activity of peptide-pyrazole conjugates. The antibacterial potency of these conjugates was evaluated against both Gram positive and Gram negative bacterial strains, increased antibacterial efficacy was found in peptide-pyrazole conjugates compared to peptides alone and simple pyrazole compounds. A molecular docking study revealed that the ligand PH3, PH4, and PH10 is very potent against key proteins. Compounds PH3, PH4, and PH10 bind near the putative binding site of DNA gyrase with the docking score of -6.54, -8.2, and -7.09 kcal/mol.

Applications of Bacteriocins of Lactic Acid Bacteria in Biotechnology and Food Preservation: A Bibliometric Review

Introduction: Due to the growing prevalence of antibiotic resistance in microorganisms and the demand for safe food, there is increasing interest in using natural bioproducts such as the antimicrobial peptides bacteriocins to extend the shelf-life of foods. This is because of their spectrum of activity, ease of synthesis and applicability. This study reports on the global trends in lactic acid bacteria (LAB) bacteriocins based research publications in the Web of Science core collections within the last 20 years (2000-2019), with specific focus to their applications in biotechnology and food science. Methods: Data analysis was undertaken using VOSviewer and HistCite software to evaluate relationships between articles and visualise research linkages amongst authors, institutions and countries. Results: In the 20 years under review, a total of 1741 bacteriocin related articles were published, with the most cited publication examining the anti-infective activity of Lactobacillus salivarius. The highest research output was recorded by the United States, followed by Spain and China. However, Europe as a continent had the highest research output with a higher inter-institution collaboration network and stronger food safety legislations. Discussion: The bibliometric analysis gave insights into the research areas, cooperation network of authors, co-citation maps and co-occurrence of keywords utilized in the research field and indicates that bacteriocin-based research is highly multidisciplinary with a global reach. Conclusion: Key focus is on the control of foodborne disease pathogens, search for new producer organisms and approaches to improve bacteriocin yield and application. This class of antimicrobial peptides has the potential to replace chemical food preservatives in the future.

In Silico Design and In Vitro Evaluation of Some Novel AMPs Derived From Human LL-37 as Potential Antimicrobial Agents for Keratitis.

The human body produces two classes of antimicrobial peptides (AMPs), namely defensins and cathelicidins. In this study, a novel decapeptide (Catoid) and its dimer (Dicatoid) based on human cathelicidin (LL-37) have been designed by bioinformatics tools to be used in the treatment of bacterial keratitis. After the selection and synthesis of peptide sequences, their antimicrobial activities against the standard and resistant strains of Pseudomonas aeruginosa and Staphylococcus aureus were evaluated. This test was performed with LL-37, gentamicin, ciprofloxacin, amikacin, and penicillin for a more accurate comparison. Furthermore, the cytotoxicity levels of the specified compounds on fibroblast cells and bovine corneal endothelial cells were investigated. The results demonstrated that the designed peptides had a superior antimicrobial activity on P. aeruginosa, compared to LL-37; however, Catoid had a better effect on the S. aureus strain. Additionally, a significant achievement is the very low toxicity level of Catoid and Dicatoid on the human skin fibroblast cell line and bovine corneal endothelial cells, compared to that of LL-37 as the initial design model.

Amyloidogenic Peptides: New Class of Antimicrobial Peptides with the Novel Mechanism of Activity.

Antibiotic-resistant bacteria are recognized as one of the leading causes of death in the world. We proposed and successfully tested peptides with a new mechanism of antimicrobial action “protein silencing” based on directed co-aggregation. The amyloidogenic antimicrobial peptide (AAMP) interacts with the target protein of model or pathogenic bacteria and forms aggregates, thereby knocking out the protein from its working condition. In this review, we consider antimicrobial effects of the designed peptides on two model organisms, E. coli and T. thermophilus, and two pathogenic organisms, P. aeruginosa and S. aureus. We compare the amino acid composition of proteomes and especially S1 ribosomal proteins. Since this protein is inherent only in bacterial cells, it is a good target for studying the process of co-aggregation. This review presents a bioinformatics analysis of these proteins. We sum up all the peptides predicted as amyloidogenic by several programs and synthesized by us. For the four organisms we studied, we show how amyloidogenicity correlates with antibacterial properties. Let us especially dwell on peptides that have demonstrated themselves as AMPs for two pathogenic organisms that cause dangerous hospital infections, and in which the minimal inhibitory concentration (MIC) turned out to be comparable to the MIC of gentamicin sulfate. All this makes our study encouraging for the further development of AAMP. The hybrid peptides may thus provide a starting point for the antibacterial application of amyloidogenic peptides.

Human Defensins from Antivirals to Vaccine Adjuvants: Rediscovery of the Innate Immunity Arsenal.

Human defensins are a class of antimicrobial peptides, belonging to the innate immunity system. These peptides are expressed at the level of respiratory tract (both upper and lower) where they represent the first line of defense against pathogens; they are also known for their activity against different viruses, acting through diverse mechanisms, including direct binding to the virus, inhibition of viral replication, and aggregation of virions. It has been recently reported they are also effective against SARS-CoV-2. Moreover, they influence the immune response stimulating it in the challenge against microorganisms. An intriguingly potential application of defensin is related to their use as vaccine adjuvants; indeed, some in silico studies suggested their efficacy in boosting the immune response. Since the long-term persistence of acquired immunity against SARS-CoV-2 triggered by the currently employed vaccines is not known, natural agents with enhancing effects, such as defensins, administered with the vaccine, can be an interesting and attractive alternative.

Bone marrow mesenchymal stem cell sheets with high expression of hBD3 and CTGF promote periodontal regeneration

The multi-bacterial environment of the oral cavity makes it hard for periodontal regeneration. As a class of antimicrobial peptide, beta defensin has been found to show broad-spectrum antibacterial ability. In addition, connective tissue growth factor (CTGF) is demonstrated to play a great role in multi-physiological events such as angiogenesis, wound healing and, more importantly, fibrogenesis. In this study, human β defensin 3 (hBD3) and CTGF were co-transfected into bone marrow derived mesenchymal stem cells (BMSCs) for preparing cell sheets. The transfection efficiency was detected through fluorescence of eGFP and western blot assay. Our results showed that the hBD3 and CTGF proteins were highly and stably expressed in the BMSCs after transfection. The results of RT-PCR and induced differentiation indicated that hBD3 promoted osteogenic differentiation of BMSCs, while CTGF significantly increased fibrogenic differentiation even in the presence of hBD3. The BMSCs acquired stronger capacity in terms of promoting M2 polarization of RAW 264.7 macrophages fulfilled by the transfection and secretion of hBD3 and CTGF. To further evaluate the periodontal remodeling performance of cell sheets, a coralline hydroxyapatite (CHA)-chitosan based hydrogel-human tooth system was designed to simulate the natural periodontal environment. The results showed that dense extracellular matrix, oriented fiber arrangement, and abundant collagen deposition appeared in the area of BMSCs sheets after subcutaneous transplantation. Altogether, our data showed that the lentivirus transfected BMSCs sheets had a promising application prospect for periodontal repair.

Increased Activities against Biofilms of the Pathogenic Yeast Candida albicans of Optimized Pom-1 Derivatives.

Antimicrobial peptides (AMPs) are an alternative group for the therapy of infectious diseases, with activity against a wide range of diverse pathogens. However, classical AMPs have significant side effects in human cells due to their unspecific pore formation in biomembranes. Nevertheless, AMPs are promising therapeutics and can be isolated from natural sources, which include sea and freshwater molluscs. The AMPs identified in these organisms show promising antimicrobial activities, as pathogens are mainly fought by innate defence mechanisms. An auspicious candidate among molluscs is the Cuban freshwater snail Pomacea poeyana, from which the peptides Pom-1 and Pom-2 have been isolated and studied. These studies revealed significant antimicrobial activities for both AMPs. Based on the activities determined, Pom-1 was used for further optimization. In order to meet the emerging requirements of improved anti-biofilm activity against naturally occurring Candida species, the six derivatives Pom-1A to F were developed and investigated. Analysis of the derivatives acting on the most abundant naturally occurring Candida yeast Candida albicans (C. albicans) revealed a strong anti-biofilm activity, especially induced by Pom-1 B, C, and D. Furthermore, a moderate decrease in the metabolic activity of planktonic yeast cells was observed.

The Main Directions of Antimicrobial Peptides Use and Synthesis Overview

In this review, various classes of antimicrobial peptides (AMPs) were collected. Majority of these peptides are an integral part of the innate immunity of living systems; most of them are non-toxic to the human body, but have a detrimental effect on viruses, bacteria, parasites, tumors and fungi, which makes them indispensable in the fight against infections, while pathogenic strains have already acquired resistance to a wide range of antibiotics. Urgent need to develop new AMPs, many laboratories around the world are now developing AMPs. For this, first, a classification of AMPs has been drawn up; secondly, the main mechanisms of AMP action on the cells of the human body and their destructive action on pathogens are being studied. According to the new classification, AMPs are sorted into antibacterial, antifungal, antiparasitic, antineoplastic, etc. classes. The main factor ensuring the attachment of AMP to the membrane of a normal cell is its charge, and the hydrophobicity of AMP contributes to the formation of pores in the membrane of the microorganism; for this reason, the activity of AMP is related to its amphiphilicity. Thus, the placement of histidine with buffering properties into AMPs provides damage to microorganisms without hemolysis of host cells; the same purpose is served by obtaining hydrophobic sites in the newly synthesized AMP. The material presented in this work helps the synthesis of new effective AMPs capable of stopping the development of severe infectious processes, with Allah Support.

The effect of piscidin antimicrobial peptides on the formation of Gram‐negative bacterial biofilms

Fish-derived antimicrobial peptides are an important part of the innate immune system due to their potent antimicrobial properties. Piscidins are a class of antimicrobial peptides first described in hybrid striped bass (Morone chrysops x Morone saxatilis) but have also been identified in many other fish species. Previous work demonstrated the broad antimicrobial activity of piscidins against Gram-negative and Gram-positive bacterial species. This study sought to determine the extent to which class I (striped bass piscidin 1, white bass piscidin 1 and striped bass/white bass piscidin 3) and class II (striped bass piscidin 4 and white bass piscidin 5) piscidins inhibit biofilm formation of different Gram-negative bacteria. In general, the class I and II piscidins demonstrate potent activity against Escherichia coli and Flavobacterium columnare biofilms. The class II piscidins showed more activity against E.coli and F.columnare isolates than did the class I piscidins. The piscidins in general were much less effective against inhibiting Aeromonas hydrophila and A.veronii biofilm growth. Only the class I piscidins showed significant growth inhibition among the Aeromonas spp. examined.

Antimicrobial peptides as an alternative to relieve antimicrobial growth promoters in poultry

ABSTRACT 1. This review describes different classes of antimicrobial peptides (AMP) found in the gastrointestinal (GI) tract of avian species, and their antimicrobial and immunomodulatory activities. The potential benefits of synthetic AMP in poultry production are examined, in the context of the use of AMP as alternatives to antimicrobial growth promoters (AGP). 2. Since the mid-1950s, antibiotic growth promoters (AGP) have been used in feed at low prophylactic doses to modulate the homoeostasis of intestinal microbiota, decreasing the risk of intestinal dysbacteriosis and the growth of pathogens within the avian gut. Over the last three decades, AGP have faced major regulatory restrictions due to concerns of generating antimicrobial resistance (AMR). It is now well documented that the rate of infectious disease outbreaks is higher in flocks that are not fed prophylactic antibiotics, resulting in a compensatory increase in antimicrobial use for therapeutic purposes. 3. Endogenous natural AMP production is associated with the presence of microbiota and their interaction with the intestinal epithelial and lamina propria lymphoid cells. Their antimicrobial activity shapes the beneficial microbiota population and controls intestinal pathogens such Clostridium and Salmonella spp., and stimulates the development and maturation of the local immune system. 4. Similar to AGP, AMP can establish a well-balanced gut beneficial microbiota for adequate immune-competence, animal health and high growth performance parameters such as feed intake, daily weight, feed conversion and accumulated mortality. 5. Antimicrobial proteins and peptides constitute an essential part of the innate immune system of all organisms and protect the host from invading pathogenic bacteria, viruses, fungi, and parasites by interacting with the negatively charged pathogen membranes.

SCREENING OF ANTI-CLOSTRIDIAL LACTIC ACID BACTERIA STRAINS ISOLATED FROM URUGUAYAN DAIRY FARMS

A total of 130 strains of lactic acid bacteria (starter lactic acid bacteria -SLAB- and non-starter lactic acid bacteria -NSLAB-) were isolated from milk, whey and cheese. Anti-clostridial activity was detected in 56 isolates against Clostridium tyrobutyricum ATCC 25755. Seven strains with the highest inhibitory activity were selected to determine their inhibitory mechanisms. Anti-clostridial activity of strains Streptococcus macedonicus 23, S. macedonicus 24, Lactobacillus casei/paracasei 29 and Lactobacillus rhamnosus 104 was due to organic acids production. Inhibitory mechanisms of strains L. casei 26 and 95 were acid production, bacteriocin and hydrogen peroxide. While anti-clostridial activity of Lactobacillus delbrueckii subsp. bulgaricus 76 was due to acid and hydrogen peroxide production. Cell-free supernatants obtained from strains 26, 95 and 76 conserved their anti-clostridial activity after thermal treatments at 70 and 100 °C. Supernatants obtained from bacteriogenic strains 26 and 95 were analyzed by RP-HPLC. RP-HPLC fractions with anti-clostridial activity were analyzed by mass spectrometry (MALDI-TOF). A peptide with molecular weight of 1162.54 Da was detected in HPLC fraction of L. casei 95. No results were obtained for MALDI-TOF analysis of another HPLC fractions. Based on the thermostability and low molecular weight, L. casei 95 anti-clostridial peptide would belong to a class I or II bacteriocin according to Gram-positive bacteria antimicrobial peptides classification.

Computational Study of Helical and Helix-Hinge-Helix Conformations of an Anti-Microbial Peptide in Solution by Molecular Dynamics and Vibrational Analysis.

Many classical antimicrobial peptides adopt an amphipathic helical structure at a water-membrane interface. Prior studies led to the hypothesis that a hinge near the middle of a helical peptide plays an important role in facilitating peptide-membrane interactions. Here, dynamics and vibrations of a designed hybrid antimicrobial peptide LM7-2 in solution were simulated to investigate its hinge formation. Molecular dynamics simulation results on the basis of the CHARMM36 force field showed that the α-helix LM7-2 bent around two or three residues near the middle of the peptide, stayed in a helix-hinge-helix conformation for a short period of time, and then returned to a helical conformation. High-resolution computational vibrational techniques were applied on the LM7-2 system when it has α-helical and helix-hinge-helix conformations to understand how this structural change affects its inherent vibrations. These studies concentrated on the calculation of frequencies that correspond to backbone amide bands I, II, and III: vibrational modes that are sensitive to changes in the secondary structure of peptides and proteins. To that end, Fourier transforms were applied to thermal fluctuations in C-N-H angles, C-N bond lengths, and C═O bond lengths of each amide group. In addition, instantaneous all-atom normal mode analysis was applied to monitor and detect the characteristic amide bands of each amide group within LM7-2 during the MD simulation. Computational vibrational results indicate that shapes and frequencies of amide bands II and especially III were altered only for amide groups near the hinge. These methods provide high-resolution vibrational information that can complement spectroscopic vibrational studies. They assist in interpreting spectra of similar systems and suggest a marker for the presence of the helix-hinge-helix motif. Moreover, radial distribution functions indicated an increase in the probability of hydrogen bonding between water and a hydrogen atom connected to nitrogen (HN) in such a hinge. The probability of intramolecular hydrogen bond formation between HN and an amide group oxygen atom within LM7-2 was lower around the hinge. No correlation has been found between the presence of a hinge and hydrogen bonds between amide group oxygen atoms and the hydrogen atoms of water molecules. This result suggests a mechanism for hinge formation wherein hydrogen bonds to oxygen atoms of water replace intramolecular hydrogen bonds as the peptide backbone folds.

Developmental and Tissue Patterns of the Basal Expression of Chicken Avian β-Defensins.

Defensins are a class of antimicrobial peptides in vertebrates that function as the first line of innate immunity with potent antimicrobial and immunomodulatory activities. Fourteen defensins, namely, avian β-defensin 1 to 14 (AvBD1-14), have been identified in chickens. Before characterizing the role of AvBDs in innate immunity during the early development of chickens, we collected tissue segments from the liver, spleen, and gastrointestinal (GI) tract including the esophagus, crop, proventriculus, gizzard, duodenum, jejunum, ileum, cecum, and colon from broilers at days 1, 3, 7, 14, and 28. After RNA isolation and reverse transcription, we determined the expression levels of the 14 AvBD genes in these tissues during the first 28 days after hatching by real-time PCR. The results suggested the AvBDs were widely expressed in the chicken liver, spleen, and gastrointestinal (GI) tract. Interestingly, we did not detect AvBD11 expressed in the GI tract, even in the liver and spleen. Additionally, AvBDs were differentially expressed in the chicken GI tract. AvBD5 and AvBD14 were expressed most abundantly in the proximal GI tract, especially the esophagus and crop. Moreover, AvBD5, AvBD7, AvBD9, and AvBD14 were expressed in an inverted-V pattern with the peak being the observed expression at days 3, 7, or 14 in the chicken spleen, esophagus, duodenum, and cecum. Other AvBDs presented biphasic or inverted-V expression patterns in different tissues. The expression levels of all detected AvBDs were strengthened after hatching rather than decreasing steadily. Therefore, AvBDs were found to be expressed widely in the chicken liver, spleen, and GI tract and their expression levels were primarily up regulated during the early development of chicken, implying the potential essential roles of AvBDs in early innate defense and infection resistance of chickens.

Wenzhouxiangella Strain AB-CW3, a Proteolytic Bacterium From Hypersaline Soda Lakes That Preys on Cells of Gram-Positive Bacteria.

A new haloalkaliphilic species of Wenzhouxiangella, strain AB-CW3, was isolated from a system of hypersaline alkaline soda lakes in the Kulunda Steppe using cells of Staphylococcus aureus as growth substrate. AB-CW3’s complete, circular genome was assembled from combined nanopore and Illumina sequencing and its proteome was determined for three different experimental conditions. AB-CW3 is an aerobic gammaproteobacterium feeding mainly on proteins and peptides. Unique among Wenzhouxiangella, it uses a flagellum for motility, fimbria for cell attachment and is capable of complete denitrification. AB-CW3 can use proteins derived from living or dead cells of Staphylococcus and other Gram-positive bacteria as the carbon and energy source. It encodes and expresses production of a novel Lantibiotic, a class of antimicrobial peptides which have so far only been found to be produced by Gram-positive bacteria. AB-CW3 likely excretes this peptide via a type I secretion system encoded upstream of the genes for production of the Lanthipeptide. Comparison of AB-CW3’s genome to 18 other Wenzhouxiangella genomes from marine, hypersaline, and soda lake habitats indicated one or two transitions from marine to soda lake environments followed by a transition of W. marina back to the oceans. Only 19 genes appear to set haloalkaliphilic Wenzhouxiangella apart from their neutrophilic relatives. As strain AB-CW3 is only distantly related to other members of the genus, we propose to provisionally name it “Wenzhouxiangella alkaliphila”.

The absence of murine cathelicidin-related antimicrobial peptide impacts host responses enhancing Salmonella enterica serovar Typhimurium infection

BackgroundCathelicidins are a class of antimicrobial peptide, and the murine cathelicidin-related antimicrobial peptide (mCRAMP) has been demonstrated in vitro to impair Salmonella enterica serovar Typhimurium proliferation. However, the impact of mCRAMP on host responses and the microbiota following S. Typhimurium infection has not been determined. In this study mCRAMP−/− and mCRAMP+/+ mice (± streptomycin) were orally inoculated with S. enterica serovar Typhimurium DT104 (SA +), and impacts on the host and enteric bacterial communities were temporally evaluated.ResultsHigher densities of the pathogen were observed in cecal digesta and associated with mucosa in SA+/mCRAMP−/− mice that were pretreated (ST+) and not pretreated (ST−) with streptomycin at 24 h post-inoculation (hpi). Both SA+/ST+/mCRAMP−/− and SA+/ST−/mCRAMP−/− mice were more susceptible to infection exhibiting greater histopathologic changes (e.g. epithelial injury, leukocyte infiltration, goblet cell loss) at 48 hpi. Correspondingly, immune responses in SA+/ST+/mCRAMP–/− and SA+/ST−/mCRAMP–/− mice were affected (e.g. Ifnγ, Kc, Inos, Il1β, RegIIIγ). Systemic dissemination of the pathogen was characterized by metabolomics, and the liver metabolome was affected to a greater degree in SA+/ST+/mCRAMP–/− and SA+/ST−/mCRAMP–/− mice (e.g. taurine, cadaverine). Treatment-specific changes to the structure of the enteric microbiota were associated with infection and mCRAMP deficiency, with a higher abundance of Enterobacteriaceae and Veillonellaceae observed in infected null mice. The microbiota of mice that were administered the antibiotic and infected with Salmonella was dominated by Proteobacteria.ConclusionThe study findings showed that the absence of mCRAMP modulated both host responses and the enteric microbiota enhancing local and systemic infection by Salmonella Typhimurium.

Cathelicidins enhance protection of channel catfish, Ictalurus punctatus, and channel catfish ♀×blue catfish, Ictalurus furcatus ♂ hybrid catfish against Edwarsiella ictaluri infection.

Cathelicidins are a class of antimicrobial peptides (AMPs) known to possess rapid and direct antimicrobial activities against a variety of microorganisms. Recently identified cathelicidins derived from alligator and sea snake were found to be more effective in inhibiting microbial growth than other AMPs previously characterized. The ability of these two cathelicidins along with the peptides, cecropin and pleurocidin, to protect channel catfish (Ictalurus punctatus, Rafinesque) and hybrid catfish (I. punctatus ♀×blue catfish, Ictalurus furcatus, Valenciennes ♂) against Edwardsiella ictaluri, one of the most prevalent pathogens affecting commercial catfish industry, was investigated. Cathelicidin-injected fish (50 µgml-1 fish-1 ) that were simultaneously challenged with E. ictaluri through bath immersion at a concentration of ~1×106 CFU/ml had increased survival rates compared with other peptide treatments and the infected control. Bacterial numbers were also reduced in the liver and kidney of channel catfish and hybrid catfish in the cathelicidin treatments 24hr post-infection. After 8days of challenge, serum was collected to determine immune-related parameters such as bactericidal activity, lysozyme, serum protein, albumin and globulin. These immune-related parameters were significantly elevated in fish injected with the two cathelicidins as compared to other peptide treatments. These results indicate that cathelicidins derived from alligator and sea snake can stimulate immunity and enhance the resistance to E. ictaluri infection in channel catfish and hybrid catfish.

Antimicrobial activity of synthetic Dq-3162, a 28-residue ponericin G-like dinoponeratoxin from the giant ant Dinoponera quadriceps venom, against carbapenem-resistant bacteria

The predatory giant ant Dinoponera quadriceps is one of the largest venomous ants on Earth. The venom of D. quadriceps comprises a rich blend of bioactive peptides that includes structures related to at least five classes of antimicrobial peptides. In the present study, two representative synthetic peptides, sDq-2562 and sDq-3162, belonging to the ponericin-like dinoponeratoxin family, were evaluated for their microbicide activity against antibiotic-resistant bacteria. The most effective peptide, the 28-residue sDq-3162 displayed a significant bacteriostatic and bactericidal effect with minimal inhibitory concentrations (MICs) between 5 μM and 10 μM (15.6 μg mL−1 and 31.2 μg mL−1), according to the strain of drug-resistant bacteria tested. In combination with conventional antibiotics, sDq-3162 displayed in vitro synergistic effects, reducing the MICs of antibiotics for more than 2-log against clinical isolates of carbapenem-resistant Acinetobacter baumannii, Klebsiella pneumoniae and Pseudomonas aeruginosa, with low cytotoxicity to human erythrocytes, in vitro. Since the development of molecules to circumvent the spread of antibiotic-resistant bacteria is demanding, ant venom peptides arise as useful molecular resources to contribute with the antimicrobial arsenal and therapeutic strategies to fight clinically relevant microbial infections.