Checkerboard testing method indicates synergic effect of pelgipeptins against multidrug resistant Klebsiella pneumoniae

Crosslinked hydrogel loaded with chitosan-supported iron oxide and silver nanoparticles as burn wound dressing

Burns can result in infection, disability, psychosocial and economic issues. Advanced wound dressings like hydrogel absorb exudate and maintain moisture. Considering the antimicrobial properties of silver nanoparticles and iron oxide nanoparticles, the efficiency of cross-linked hydrogel loaded with chitosan-supported iron oxide and silver nanoparticles for burn wounds repair was investigated in animal model. Cellulose hydrogel dressing made from carboxymethylcellulose and hydroxyethylcellulose crosslinked with different concentrations of citric acid (10, 15, 20, and 30%) was produced. The physicochemical characteristics of the synthetized hydrogels including Fourier-Transform Infrared spectroscopy, Thermal behavior, Swelling properties, and Scanning Electron Microscope (SEM) were evaluated. The silver nanoparticles and iron nanoparticles were produced and the characteristics, cytotoxicity, antimicrobial activities and their synergistic effect were investigated. After adding nanoparticles to hydrogels, the effects of the prepared wound dressings were investigated in a 14-day animal model of burn wound. The results showed that the mixture comprising 12.5 ppm AgNps, and IONPs at a concentration ≤100 ppm was non-cytotoxic. Moreover, the formulations with 20% CA had a swelling ratio of almost 250, 340, and 500 g/g at pHs of 5, 6.2, and 7.4 after one hour, which are lower than those of formulations with 5 and 10% CA. The total mass loss (59.31%) and the exothermic degradation happened in the range of 273-335 °C and its Tm was observed at 318.52 °C for hydrogels with 20% CA. Thus, the dressing comprising 20% CA which was loaded with 12.5 ppm silver nanoparticles (AgNPs) and 100 ppm iron oxide nanoparticles (IONPs) indicated better physicochemical, microbial and non-cytotoxic characteristics, and accelerated the process of wound healing after 14 days. It was concluded that the crosslinked hydrogel loaded with 12.5 ppm AgNPs and 100 ppm IONPs possesses great wound healing activity and could be regarded as an effective topical burn wound healing treatment.

Superior Performance of Iron-Coated Silver Nanoparticles and Cefoxitin as an Antibiotic Composite Against Methicillin-Resistant Staphylococcus aureus (MRSA): A Population Study

The synergistic effects of antimicrobial nanostructures with antibiotics present a promising solution for overcoming resistance in methicillin-resistant Staphylococcus aureus (MRSA). Previous studies have introduced iron as a novel coating for silver nanoparticles (AgNPs) to enhance both economic efficiency and potency against S. aureus. However, there are currently no available data on the potential of these novel nanostructures to reverse MRSA resistance. To address this gap, a population study was conducted within the MRSA community, collecting a total of 48 S. aureus isolates from skin lesions. Among these, 21 isolates (43.75%) exhibited cefoxitin resistance as determined by agar disk diffusion assay. Subsequently, a PCR test confirmed the presence of the mecA gene in 20 isolates, verifying them as MRSA. These results highlight the cefoxitin disk diffusion susceptibility test as an accurate screening method for predicting mecA-mediated resistance in MRSA. Synergy tests were performed on cefoxitin, serving as a marker antibiotic, and iron-coated AgNPs (Fe@AgNPs) in a combination study using the checkerboard assay. The average minimal inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of cefoxitin were calculated as 11.55 mg/mL and 3.61 mg/mL, respectively. The findings indicated a synergistic effect (FIC index < 0.5) between Fe@AgNPs and cefoxitin against 90% of MRSA infections, while an additive effect (0.5 ≤ FIC index ≤ 1) could be expected in 10% of infections. These results suggest that Fe@AgNPs could serve as an economically viable candidate for co-administration with antibiotics to reverse resistance in MRSA infections within skin lesions. Such findings may pave the way for the development of future treatment strategies against MRSA infections.

Action of crude ethanol extract of Hymenaea martiana leaf, gallic acid, and polypyrrole (PPy) against Aeromonas hydrophila

Pisciculture represents one of the industries with the fastest growth rates worldwide. However, it presents obstacles to its development, such as bacteriosis, which is conventionally treated with antibiotics. The indiscriminate and inappropriate use of antibiotics can lead to bacterial resistance, thus alternatives to the use of antibiotics have been researched. The study aimed to analyze the potential of crude ethanol extract (CEE) from Hymenaea martiana leaf, gallic acid (GA), and polypyrrole (PPy) against Aeromonas hydrophila. Tests were performed to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the compounds individually and in synergy (checkerboard) against A. hydrophila and in silico tests between the compounds evaluated. The CEE of H. martiana leaf and PPy were effective against A. hydrophila with MBC results of 3125 μg/mL for the CEE of H. martiana and 125 μg/mL for PPy. Evaluating the GA, a MIC and MBC of 125 μg/mL was obtained. In the interaction tests (checkerboard, using PPy/CEE and PPy/GA), there was a significant reduction in individual introductions. Thus, for the PPy/CEE tests, we had a reduction of MIC/MBC to 1.95 and 781.25 μg/mL, and for the synergy tests between PPy/GA to 7.8125 and 31.125 μg/mL, respectively. The synergy tests are encouraging, and it is possible to verify a decrease of up to 98% in the introduction of PPy, 75% in CEE for H. martiana and 75.1% for GA, when compared to their individual tests. The tests with GA are encouraging due to GA's effectiveness as an antimicrobial agent and high synergy with polypyrrole, both in vitro results and molecular docking experiments showed the actions at the same activation site in A. hydrophila. In vivo tests evaluating isolated components of CEE from H. martiana in synergy with PPy should be performed, to verify the quality of the interactions and the improvement of the immune responses of the animals. It was evidenced that gallic acid, a substance isolated from the extract, tends to have more promising results. This is relevant since the industry has been developing these compounds for different uses, thus providing easier access to the product. Thus, the present study indicates an efficient alternative in the use of bioactive compounds as substitutes for conventional antimicrobials.

Pelgipeptins, a Nonribosomal Lipopeptide Family, Show Larvicidal Activity against Vectors Transmitting Viruses

Aedes aegypti and Culex quinquefasciatus are vectors of numerous diseases of worldwide public importance, such as arboviruses and filariasis. The main strategy for controlling these vectors is the use of chemicals, which can induce the appearance of resistant insects. The use of Bacillus thuringiensis (Bt) and Lysinibacillus sphaericus (Ls) with larvicidal activity against arboviral-transmitting insects has been successful in many studies. In contrast, the use and knowledge of peptides with insecticidal activity are so far scarce. In this work, 25 peptides and 5 strains of each bacterial species were prospected individually or together regarding their insecticidal activity. Initially, in vitro assays of cellular cytotoxicity of the peptides against SF21 cells of Spodoptera frugiperda were performed. The peptides Polybia-MPII and pelgipeptin caused 69 and 60% of cell mortality, respectively, at the concentration of 10 μM. Thus, they were evaluated in vivo against second-stage larvae of the two Culicidae. However, in the in vivo bioassays, only pelgipeptin showed larvicidal mortality against both larvae (LC₅₀ 6.40 μM against A. aegypti, and LC₅₀ 1.22 μM against C. quinquefasciatus). The toxin-producing bacterial strain that showed the lowest LC₅₀ against A. aegypti was Bt S8 (LC₅₀ = 0.71 ng/mL) and against C. quinquefasciatus, it was Ls S260 (LC₅₀ = 2.32 ng/mL). So, the synergistic activity between the association of the bacterial toxins and pelgipeptin was evaluated. A synergic effect of pelgipeptin was observed with Ls strain S260 against C. quinquefasciatus. Our results demonstrate the possibility of synergistic or individual use of both biologically active larvicides against C. quinquefasciatus and A. aegypti.

A novel family of non-secreted tridecaptin lipopeptide produced by Paenibacillus elgii

Bacteria from the genus Paenibacillus make a variety of antimicrobial compounds, including lipopeptides produced by a non-ribosomal synthesis mechanism (NRPS). In the present study, we show the genomic and phenotypical characterization of Paenibacillus elgii AC13 which makes three groups of small molecules: the antimicrobial pelgipeptins and two other families of peptides that have not been described in P. elgii. A family of lipopeptides with [M + H]⁺ 1664, 1678, 1702, and 1717 m/z was purified from the culture cell fraction. Partial characterization revealed that they are similar to tridecaptin from P. terrae. However, they present amino acid chain modifications in positions 3, 7, and 10. These new variants were named tridecaptin G1, G2, G3, and G4. Furthermore, a gene cluster was identified in P. elgii AC13 genome, revealing high similarity to the tridecaptin-NRPS gene cluster from P. terrae. Tridecaptin G1 and G2 showed in vitro antimicrobial activity against Escherichia coli, Klebsiella pneumonia (including a multidrug-resistant strain), Staphylococcus aureus, and Candida albicans. Tri G3 did not show antimicrobial activity against S. aureus and C. albicans at all tested concentrations. An intriguing feature of this family of lipopeptides is that it was only observed in the cell fraction of the P. elgii AC13 culture, which could be a result of the amino acid sequence modifications presented in these variants.

The Emergence of Carbapenem-Resistant Gram-Negative Bacteria in Mizoram, Northeast India

(Background) Numerous reports on carbapenem resistance in different parts of India have been published, yet there are insufficient studies on the prevalence of antibiotic resistance in the northeast region of the country. This study evaluated the emergence of carbapenem resistance in the clinical isolates collected in Mizoram. (Results) A total of 141 Gram-negative clinical isolates were collected from the two hospitals, including the Civil Hospital in Lunglei and the Synod Hospital in Aizawl. The isolates include Escherichia coli (n = 62, 43.9%), Klebsiella spp. (n = 43, 30.4%), Pseudomonas aeruginosa (n = 9, 6.3%), Serratia marcescens (n = 3, 2.1%), Proteus mirabilis (n = 2, 1.4%), Shigella spp. (n = 4, 2.8%), Enterobacter spp. (n = 6, 4.2%) and Acinetobacter spp. (n = 12, 8.5%). The isolates were found to be resistant to meropenem (11%), colistin (48%), tigecycline (25%) and cefotaxime (50%). A total of four E. coli and one Shigella sonnei encoded the blaOXA-48-like gene. The blaCTX-M-1 gene was detected in 13 isolates, of which eight were E. coli, two Shigella flexneri, and one isolates each of K. pneumoniae, K. oxytoca and Shigella sonnei, respectively. (Conclusion) Carbapenem-resistant Enterobacteriaceae are common among other parts of India, despite limited access to antibiotics, the emergence of resistance in the northeastern region is worrying.

Gentamicin Augments the Quorum Quenching Potential of Cinnamaldehyde In Vitro and Protects Caenorhabditis elegans From Pseudomonas aeruginosa Infection

The quorum sensing (QS) circuitry of Pseudomonas aeruginosa represents an attractive target to attenuate bacterial virulence and antibiotic resistance. In this context, phytochemicals harboring anti-virulent properties have emerged as an alternative medicine to combat pseudomonal infections. Hence, this study was undertaken to investigate the synergistic effects and quorum quenching (QQ) potential of cinnamaldehyde (CiNN) in combination with gentamicin (GeN) against P. aeruginosa. The QQ activity of this novel combination was evaluated using a QS reporter strain and synergism was studied using chequerboard assays. Further, the genotypic and phenotypic expression of pseudomonal virulence factors was examined alongside biofilm formation. The combination of CiNN and GeN exhibited synergy and promising anti-QS activity. This drug combination was shown to suppress AHL production and downregulate the expression of critical QS genes in P. aeruginosa PAO1. Molecular docking revealed strong interactions between the QS receptors and CiNN, asserting its QQ potential. Bacterial motility was compromised along with a significant reduction in pyocyanin (72.3%), alginate (58.7%), rhamnolipid (33.6%), hemolysin (82.6%), protease (70.9%), and elastase (63.9%) production. The drug combination successfully eradicated preformed biofilms and inhibited biofilm formation by abrogating EPS production. Our findings suggest that although GeN alone could not attenuate QS, but was able to augment the anti-QS potential of CiNN. To validate our results using an infection model, we quantified the survival rates of Caenorhabditis elegans following PAO1 challenge. The combination significantly rescued C. elegans from PAO1 infection and improved its survival rate by 54% at 96 h. In summary, this study is the first to elucidate the mechanism behind the QQ prospects of CiNN (augmented in presence of GeN) by abrogating AHL production and increasing the survival rate of C. elegans, thereby highlighting its anti-virulent properties.

Co-occurrence of linear and cyclic pelgipeptins in broth cultures of Paenibacillus elgii AC13

Paenibacillus elgii AC13 produces antimicrobial lipopeptides of agricultural and pharmaceutical importance. It secretes four cyclic lipopeptides named pelgipeptins, previously characterized in P. elgii B69. These lipopeptides result from the expression of a nonribosomal peptide gene cluster. P. elgii AC13 also produced two linear lipopeptides with ratios of [M + H] + 1105 and 1119 m/z. These compounds were previously observed in Paenibacillus sp. strain OSY-N, but due to purification difficulties, their characterization was executed using synthetically produced linear pelgipeptins. In the present study, purification was achieved from the supernatants of cultures from three complex media by high-performance liquid chromatography. The partial characterization of linear pelgipeptins revealed the similar antimicrobial activity and cytotoxicity of their synthetically produced counterparts, known as paenipeptins. Cyclic forms were highly stable to changes in pH, temperature, and organic extraction with n-butanol as shown by mass spectrometry (MALDI-TOF); therefore, these steps did not cause the hydrolysis of pelgipeptins. A low-activity thioesterase could also generate the linear isoforms observed; this enzyme catalyzes the cyclization process and is coded in the same gene cluster. Alternatively, the cyclic forms were hydrolyzed by an unknown protease produced during growth in the complex medium used in the present study. Although culture conditions are known to produce pelgipeptins with different yields and amino acid compositions, the occurrence of linear and cyclic forms simultaneously has not yet been reported. A mixture of cyclic and linear pelgipeptins presents a potential advantage of the higher antimicrobial activity of cyclic forms combined with the lower cytotoxicity of linear isoforms.

In vitro antifungal activity of pelgipeptins against human pathogenic fungi and Candida albicans biofilms

Systemic mycoses have become a major cause of morbidity and mortality, particularly among immunocompromised hosts and long-term hospitalized patients. Conventional antifungal agents are limited because of not only their costs and toxicity but also the rise of resistant strains. Lipopeptides from Paenibacillus species exhibit antimicrobial activity against a wide range of human and plant bacterial pathogens. However, the antifungal potential of these compounds against important human pathogens has not yet been fully evaluated, except for Candida albicans. Paenibacillus elgii produces a family of lipopeptides named pelgipeptins, which are synthesized by a non-ribosomal pathway, such as polymyxin. The present study aimed to evaluate the activity of pelgipeptins produced by P. elgii AC13 against Cryptococcus neoformans, Paracoccidioides brasiliensis, and Candida spp. Pelgipeptins were purified from P. elgii AC13 cultures and characterized by high-performance liquid chromatography (HPLC) and mass spectrometry (MALDI-TOF MS). The in vitro antifugal activity of pelgipeptins was evaluated against C. neoformans H99, P. brasiliensis PB18, C. albicans SC 5314, Candida glabrata ATCC 90030, and C. albicans biofilms. Furthermore, the minimal inhibitory concentration (MIC) was determined according to the CLSI microdilution method. Fluconazole and amphotericin B were also used as a positive control. Pelgipeptins A to D inhibited the formation and development of C. albicans biofilms and presented activity against all tested microorganisms. The minimum inhibitory concentration values ranged from 4 to 64 µg/mL, which are in the same range as fluconazole MICs. These results highlight the potential of pelgipeptins not only as antimicrobials against pathogenic fungi that cause systemic mycoses but also as coating agents to prevent biofilm formation on medical devices.

EcDBS1R4, an Antimicrobial Peptide Effective against Escherichia coli with In Vitro Fusogenic Ability

Discovering antibiotic molecules able to hold the growing spread of antimicrobial resistance is one of the most urgent endeavors that public health must tackle. The case of Gram-negative bacterial pathogens is of special concern, as they are intrinsically resistant to many antibiotics, due to an outer membrane that constitutes an effective permeability barrier. Antimicrobial peptides (AMPs) have been pointed out as potential alternatives to conventional antibiotics, as their main mechanism of action is membrane disruption, arguably less prone to elicit resistance in pathogens. Here, we investigate the in vitro activity and selectivity of EcDBS1R4, a bioinspired AMP. To this purpose, we have used bacterial cells and model membrane systems mimicking both the inner and the outer membranes of Escherichia coli, and a variety of optical spectroscopic methodologies. EcDBS1R4 is effective against the Gram-negative E. coli, ineffective against the Gram-positive Staphylococcus aureus and noncytotoxic for human cells. EcDBS1R4 does not form stable pores in E. coli, as the peptide does not dissipate its membrane potential, suggesting an unusual mechanism of action. Interestingly, EcDBS1R4 promotes a hemi-fusion of vesicles mimicking the inner membrane of E. coli. This fusogenic ability of EcDBS1R4 requires the presence of phospholipids with a negative curvature and a negative charge. This finding suggests that EcDBS1R4 promotes a large lipid spatial reorganization able to reshape membrane curvature, with interesting biological implications herein discussed.

Strategies for recombinant production of antimicrobial peptides with pharmacological potential

INTRODUCTION

The need to develop new drugs for the control of pathogenic microorganisms has redoubled efforts to prospect for antimicrobial peptides (AMPs) from natural sources and to characterize its structure and function. These molecules present a broad spectrum of action against different microorganisms and frequently present promiscuous action, with anticancer and immunomodulatory activities. Furthermore, AMPs can be used as biopharmaceuticals in the treatment of hospital-acquired infections and other serious diseases with relevant social and economic impacts.Areas covered: The low yield and the therefore difficult extraction and purification process in AMPs are problems that limit their industrial application and scientific research. Thus, optimized heterologous expression systems were developed to significantly boost AMP yields, allow high efficiency in purification and structural optimization for the increase of therapeutic activity.Expert opinion: This review provides an update on recent developments in the recombinant production of ribosomal and non-ribosomal synthesis of AMPs and on strategies to increase the expression of genes encoding AMPs at the transcriptional and translational levels and regulation of the post-translational modifications. Moreover, there are detailed reports of AMPs that have already reached marketable status or are in the pipeline under advanced stages of preclinical testing.

Structure and antifungal activity of pelgipeptins from Paenibacillus elgii against phytopathogenic fungi

Paenibacillus elgii JCK1400 shows strong antifungal activity against various plant pathogenic fungi in vitro, but little is known about its mode of action. Four antifungal lipopeptides were isolated from P. elgii JCK1400 using bioassay-directed fractionation. Their chemical structures were determined to be pelgipeptins (PGPs) using electrospray ionization tandem mass spectrometry (ESI-MS/MS) and nuclear magnetic resonance (NMR) spectroscopy. Among the four lipopeptides, PGP-C showed the strongest mycelial growth inhibitory activity against several plant pathogenic fungi-with minimum inhibitory concentration (MIC) values ranging from 4 to 32 μg mL^-1-followed by PGP-D, -A, and -B. In pot experiments, PGP-C also effectively suppressed the development of important fungal diseases in crops. In particular, PGP-C was effective in controlling tomato grey mold and wheat leaf rust, with control values of 91% and 73%, respectively, at a concentration of 125 μg mL^-1. The fermentation broth of the antagonistic bacterium reduced the development of creeping bentgrass dollar spot and Kentucky bluegrass brown patch in a dose-dependent manner. However, our study on the effect of PGP-C on the fungal cell membrane-using microscopic observation with propidium iodide (PI) fluorescence-indicated that PGP-C does not target the fungal cell walls, but instead targets the cell membranes. This is the first study to report the in vitro and in vivo antifungal activity of PGP-C against various plant pathogenic fungi. Our results suggest that P. elgii JCK1400, which produces PGPs, could serve as a potential biocontrol agent for plant diseases caused by various fungi.

Biological Control of Tomato Bacterial Wilt, Kimchi Cabbage Soft Rot, and Red Pepper Bacterial Leaf Spot Using Paenibacillus elgii JCK-5075

The over and repeated use of chemical bactericides to control plant bacterial diseases has resulted in unwanted effects, such as environmental pollution, residual toxicity, and resistance buildup in bacterial pathogens. Many previous studies have aimed to develop biological control agents to replace chemical bactericides. In this study, the antibacterial efficacy of the fermentation broth of Paenibacillus elgii JCK-5075 and its antibacterial compounds were evaluated against plant pathogenic bacteria, using both in vitro and in vivo bioassays. Pelgipeptins (PGPs) A, B, C, and D that were isolated from P. elgii JCK-5075 displayed broad-spectrum antibacterial activity against various plant pathogenic bacteria. The fermentation broth of P. elgii JCK-5075, at 5-fold dilution, effectively suppressed the development of tomato bacterial wilt, Kimchi cabbage soft rot, and red pepper bacterial leaf spot in pot experiments with control values of 81, 84, and 67%, respectively. PGP-A and C, at 200 μg/ml, were also found to markedly reduce the development of Kimchi cabbage bacterial soft rot by 75% and tomato bacterial wilt by 83%, respectively, and their disease control efficacy was comparable to that of oxolinic acid with control values of 81 and 85%, respectively. Additionally, the antibacterial activity of PGP-C was found to be directly correlated with membrane damage mechanisms. These results indicates that P. elgii JCK-5075 producing PGPs could be used as a biocontrol agent for the control of plant bacterial diseases. This is the first report on the in vitro and in vivo antibacterial activity of PGPs against bacterial plant pathogens.

A Systematic Review on Synthetic Drugs and Phytopharmaceuticals Used to Manage Diabetes

BACKGROUND

Diabetes is a multifactorial disease and a major cause for many microvascular and macrovascular complications. The disease will ultimately lead to high rate mortality if it is not managed properly. Treatment of diabetes without any side effects has always remained a major challenge for health care practitioners.

INTRODUCTION

The current review discusses the various conventional drugs, herbal drugs, combination therapy and the use of nutraceuticals for the effective management of diabetes mellitus. The biotechnological aspects of various antidiabetic drugs are also discussed.

METHODS

Structured search of bibliographic databases for previously published peer-reviewed research papers was explored and data was sorted in terms of various approaches that are used for the treatment of diabetes.

RESULTS

More than 170 papers including both research and review articles, were included in this review in order to produce a comprehensive and easily understandable article. A series of herbal and synthetic drugs have been discussed along with their current status of treatment in terms of dose, mechanism of action and possible side effects. The article also focuses on combination therapies containing synthetic as well as herbal drugs to treat the disease. The role of pre and probiotics in the management of diabetes is also highlighted.

CONCLUSION

Oral antihyperglycemics which are used to treat diabetes can cause many adverse effects and if given in combination, can lead to drug-drug interactions. The combination of various phytochemicals with synthetic drugs can overcome the challenge faced by the synthetic drug treatment. Herbal and nutraceuticals therapy and the use of probiotics and prebiotics are a more holistic therapy due to their natural origin and traditional use.