Antimicrobial Activity of Plectasin NZ2114 in Combination with Cell Wall Targeting Antibiotics Against VanA-Type Enterococcus faecalis

Antimicrobial peptide plectasin recombinantly produced in Escherichia coli disintegrates cell walls of gram-positive bacteria, as proven by transmission electron and atomic force microscopy

Plectasin, an antimicrobial peptide, was initially isolated from the saprophytic fungus Pseudoplectania nigrella. This peptide, a member of the cysteine-stabilized α-helix and β-sheet family, has demonstrated potent antimicrobial activity against gram-positive pathogens, including strains resistant to conventional antibiotics. Our CASPON platform process enables the production of substantial quantities of plectasin, facilitating investigations on the activity and the mode of action of this recombinantly produced peptide. To this end, we developed an activity assay that reflects the growth inhibition of selected model bacteria, allowing for statistical analysis and evaluation of reproducibility. The mode of action was investigated using transmission electron microscopy and atomic force microscopy. The latter provided new insights into alterations in the cell surface of gram-positive bacteria treated with plectasin at the single-cell level. While the cell diameter remained unaltered, the roughness increased by up to twofold, and the cell stiffness decreased by approximately one-third in the four gram-positive bacterial strains tested. Statistical analysis of these morphological changes provides further insights into the effects and efficiency of antimicrobial peptides targeting pathogen cell walls.

IMPORTANCE

The rise of antibiotic-resistant bacteria is a major threat to global health. Antimicrobial peptides (AMPs) offer a promising way to combat this. With the CASPON technology, we produced the AMP plectasin comprising three disulfide bonds using Escherichia coli. The activity of purified plectasin with and without a CASPON fusion tag was determined for four gram-positive and four gram-negative bacteria. As anticipated, only gram-positive bacteria showed a growth inhibition response to un-tagged plectasin. Plectasin treatment on gram-positive bacteria was visualized via electron microscopy. Evaluation of atomic force microscopy indicated that plectasin treatment led to increased roughness but maintained thickness. Based on our study, we assume that the CASPON technology can be employed in the future for the production and characterization of medical-grade AMPs.

Complementary Activities of Host Defence Peptides and Antibiotics in Combating Antimicrobial Resistant Bacteria

Due to their ability to eliminate antimicrobial resistant (AMR) bacteria and to modulate the immune response, host defence peptides (HDPs) hold great promise for the clinical treatment of bacterial infections. Whereas monotherapy with HDPs is not likely to become an effective first-line treatment, combinations of such peptides with antibiotics can potentially provide a path to future therapies for AMR infections. Therefore, we critically reviewed the recent literature regarding the antibacterial activity of combinations of HDPs and antibiotics against AMR bacteria and the approaches taken in these studies. Of the 86 studies compiled, 56 featured a formal assessment of synergy between agents. Of the combinations assessed, synergistic and additive interactions between HDPs and antibiotics amounted to 84.9% of the records, while indifferent and antagonistic interactions accounted for 15.1%. Penicillin, aminoglycoside, fluoro/quinolone, and glycopeptide antibiotic classes were the most frequently documented as interacting with HDPs, and Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium were the most reported bacterial species. Few studies formally evaluated the effects of combinations of HDPs and antibiotics on bacteria, and even fewer assessed such combinations against bacteria within biofilms, in animal models, or in advanced tissue infection models. Despite the biases of the current literature, the studies suggest that effective combinations of HDPs and antibiotics hold promise for the future treatment of infections caused by AMR bacteria.

Probiotics and Their Bioproducts: A Promising Approach for Targeting Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococcus

Antibiotic resistance is a serious global health problem that poses a threat to the successful treatment of various bacterial infections, especially those caused by methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). Conventional treatment of MRSA and VRE infections is challenging and often requires alternative or combination therapies that may have limited efficacy, higher costs, and/or more adverse effects. Therefore, there is an urgent need to find new strategies to combat antibiotic-resistant bacteria. Probiotics and antimicrobial peptides (AMPs) are two promising approaches that have shown potential benefits in various diseases. Probiotics are live microorganisms that confer health benefits to the host when administered in adequate amounts. AMPs, usually produced with probiotic bacteria, are short amino acid sequences that have broad-spectrum activity against bacteria, fungi, viruses, and parasites. Both probiotics and AMPs can modulate the host immune system, inhibit the growth and adhesion of pathogens, disrupt biofilms, and enhance intestinal barrier function. In this paper, we review the current knowledge on the role of probiotics and AMPs in targeting multi-drug-resistant bacteria, with a focus on MRSA and VRE. In addition, we discuss future directions for the clinical use of probiotics.

Anti-Pseudomonas aeruginosa activity of natural antimicrobial peptides when used alone or in combination with antibiotics

The World Health Organization has recently published a list of 12 drug-resistant bacteria that posed a significant threat to human health, and Pseudomonas aeruginosa (P. aeruginosa) was among them. In China, P. aeruginosa is a common pathogen in hospital acquired pneumonia, accounting for 16.9-22.0%. It is a ubiquitous opportunistic pathogen that can infect individuals with weakened immune systems, leading to hospital-acquired acute and systemic infections. The excessive use of antibiotics has led to the development of various mechanisms in P. aeruginosa to resist conventional drugs. Thus, there is an emergence of multidrug-resistant strains, posing a major challenge to conventional antibiotics and therapeutic approaches. Antimicrobial peptides are an integral component of host defense and have been found in many living organisms. Most antimicrobial peptides are characterized by negligible host toxicity and low resistance rates, making them become promising for use as antimicrobial products. This review particularly focuses on summarizing the inhibitory activity of natural antimicrobial peptides against P. aeruginosa planktonic cells and biofilms, as well as the drug interactions when these peptides used in combination with conventional antibiotics. Moreover, the underlying mechanism of these antimicrobial peptides against P. aeruginosa strains was mainly related to destroy the membrane structure through interacting with LPS or increasing ROS levels, or targeting cellular components, leaded to cell lysis. Hopefully, this analysis will provide valuable experimental data on developing novel compounds to combat P. aeruginosa.

Antimicrobial Peptide Synergies for Fighting Infectious Diseases

Antimicrobial peptides (AMPs) are essential elements of thehost defense system. Characterized by heterogenous structures and broad-spectrumaction, they are promising candidates for combating multidrug resistance. Thecombined use of AMPs with other antimicrobial agents provides a new arsenal ofdrugs with synergistic action, thereby overcoming the drawback of monotherapiesduring infections. AMPs kill microbes via pore formation, thus inhibitingintracellular functions. This mechanism of action by AMPs is an advantage overantibiotics as it hinders the development of drug resistance. The synergisticeffect of AMPs will allow the repurposing of conventional antimicrobials andenhance their clinical outcomes, reduce toxicity, and, most significantly,prevent the development of resistance. In this review, various synergies ofAMPs with antimicrobials and miscellaneous agents are discussed. The effect ofstructural diversity and chemical modification on AMP properties is firstaddressed and then different combinations that can lead to synergistic action,whether this combination is between AMPs and antimicrobials, or AMPs andmiscellaneous compounds, are attended. This review can serve as guidance whenredesigning and repurposing the use of AMPs in combination with other antimicrobialagents for enhanced clinical outcomes.

Promising Methods of Antibacterial Finishing of Textile Materials

A review article, containing information on the options, possibilities, and prospects for the development of antibacterial finishing of textile materials, is presented. A wide range of products designed to impart antibacterial, antimicrobial, and antiviral properties to textile materials is considered. The main factors determining the appropriate decision on the technological and functional choice of the protective composition are presented, including the nature of the fiber-forming polymer, the tasks that the resulting material is designed to solve, and its application options. Compositions providing the required effect of destruction of the pathogenic flora and their application technologies are described. Special attention is paid to antimicrobial agents based on silver nanoparticles. Nanoparticles of this metal have a detrimental effect on antibiotic-resistant strains of bacteria; their effectiveness is higher as compared to a number of well-known antibiotics, for example, penicillin and its analogues. Silver nanoparticles are harmless to the human body. Acting as an inhibitor, they limit the activity of the enzyme responsible for oxygen consumption by single-cell bacteria, viruses, and fungi. In this case, silver ions bind to the outer and inner proteins of the bacterial cell membranes, blocking cellular respiration and reproduction. Various options to apply microencapsulation methods for the implementation of antibacterial finishing are considered, including: phase separation, suspension crosslinking, simple and complex coacervation, spray drying, crystallization from the melt, evaporation of the solvent, co-extrusion, layering, fluidized bed spraying, deposition, emulsion and interphase polymerization, layer-by-layer electrostatic self-assembly etc. All presented technologies are at various development stages-from the laboratory stage to production tests, they all have certain advantages and disadvantages. The accelerated development and implementation of the described methods in production of textile materials is relevant and is related to the existing complex epidemiological situation in the world.

Clinical Pharmacokinetics and Pharmacodynamics of Imipenem-Cilastatin/Relebactam Combination Therapy

On 16 July, 2019, the US Food and Drug Administration approved imipenem-cilastatin/relebactam (Recarbrio™) for the treatment of adults with complicated urinary tract infections and complicated intra-abdominal infections. This decision was based on substantial clinical and pre-clinical data, including rigorous pharmacokinetic and pharmacodynamic work, and is an important step forward in the management of these debilitating conditions. This article provides an overview of the body of research associated with imipenem-cilastatin/relebactam, beginning with an examination of the fundamental underpinnings of the pharmacokinetic/pharmacodynamic index. This is followed by the pharmacokinetic/pharmacodynamic work that led to the approval of this novel drug combination, including data derived from checkerboard and hollow fiber infection studies, as well as large, multi-center, phase III clinical trials known as RESTORE-IMI 1 and RESTORE-IMI 2. The article also explores how this important new antibiotic may be used to treat other infections in the years to come, including hospital-acquired bacterial pneumonia and ventilator-associated pneumonia attributed to imipenem-non-susceptible pathogens and certain atypical mycobacterial infections.

The Pharmacodynamics Study of Insect Defensin DLP4 Against Toxigenic Staphylococcus hyicus ACCC 61734 in Vitro and Vivo

Staphylococcus hyicus (S. hyicus), as the main pathogen of exudative epidermitis (EE) in piglet, can cause a wide variety of diseases, ranging from bovine mastitis, chicken arthritis and even human sepsis, which has brought serious threats to animals and human. The potential threat of S. hyicus infection to both public and animal health has aroused great concern. The aim of our study was to explore the efficacy of insect defensin DLP4 against S. hyicus ACCC 61734 in vitro and in vivo. The in vitro efficacies of DLP4 against S. hyicus ACCC 61734 showed high antibacterial activity (0.92 μM), a long postantibiotic effect (9.54 h), a synergistic effect with ceftriaxone, penicillin and amoxicillin, a stable bacteriostatic effect, and intracellular bacteriostatic activity against S. hyicus ACCC 61734 in HaCaT cells. Besides, the antibacterial mechanism of DLP4 against S. hyicus ACCC 61734 was explored for the first time, which indicated that the antibacterial effect of DLP4 was related to its ability to destroy cell wall and generate membrane vesicles. The in vivo therapeutic effect of DLP4 was evaluated through mouse abscess model, and the results showed that DLP4 could effectively alleviate the mouse skin abscess by inhibiting bacterial proliferation and regulating cytokines. This study first demonstrated that DLP4 may be a promising therapeutic agent against S. hyicus ACCC 61734 infection.

Fosfomycin as Partner Drug for Systemic Infection Management. A Systematic Review of Its Synergistic Properties from In Vitro and In Vivo Studies

Fosfomycin is being increasingly prescribed for multidrug-resistant bacterial infections. In patients with systemic involvement, intravenous fosfomycin is usually administered as a partner drug, as part of an antibiotic regimen. Hence, the knowledge of fosfomycin pharmacodynamic interactions (synergistic, additive, indifferent and antagonistic effect) is fundamental for a proper clinical management of severe bacterial infections. We performed a systematic review to point out fosfomycin's synergistic properties, when administered with other antibiotics, in order to help clinicians to maximize drug efficacy optimizing its use in clinical practice. Interactions were more frequently additive or indifferent (65.4%). Synergism accounted for 33.7% of total interactions, while antagonism occurred sporadically (0.9%). Clinically significant synergistic interactions were mostly distributed in combination with penicillins (51%), carbapenems (43%), chloramphenicol (39%) and cephalosporins (33%) in Enterobactaerales; with linezolid (74%), tetracyclines (72%) and daptomycin (56%) in Staphylococcus aureus; with chloramphenicol (53%), aminoglycosides (43%) and cephalosporins (36%) against Pseudomonas aeruginosa; with daptomycin (97%) in Enterococcus spp. and with sulbactam (75%) and penicillins (60%) and in Acinetobacter spp. fosfomycin-based antibiotic associations benefit from increase in the bactericidal effect and prevention of antimicrobial resistances. Taken together, the presence of synergistic interactions and the nearly total absence of antagonisms, make fosfomycin a good partner drug in clinical practice.

Multitarget Approaches against Multiresistant Superbugs

Despite efforts to develop new antibiotics, antibacterial resistance still develops too fast for drug discovery to keep pace. Often, resistance against a new drug develops even before it reaches the market. This continued resistance crisis has demonstrated that resistance to antibiotics with single protein targets develops too rapidly to be sustainable. Most successful long-established antibiotics target more than one molecule or possess targets, which are encoded by multiple genes. This realization has motivated a change in antibiotic development toward drug candidates with multiple targets. Some mechanisms of action presuppose multiple targets or at least multiple effects, such as targeting the cytoplasmic membrane or the carrier molecule bactoprenol phosphate and are therefore particularly promising. Moreover, combination therapy approaches are being developed to break antibiotic resistance or to sensitize bacteria to antibiotic action. In this Review, we provide an overview of antibacterial multitarget approaches and the mechanisms behind them.

A new high-yielding antimicrobial peptide NZX and its antibacterial activity against Staphylococcus hyicus in vitro/vivo

Staphylococcus hyicus, considered as a leading pathogen of exudative epidermitis, is a serious threat to humans and animals. The emergency of bacterial resistance to antibiotics, especially in human and animal health fields, leads to an urgent need of exploration of new antimicrobial agents. In this study, NZX, a plectasin-derived peptide, was firstly expressed in Pichia pastoris X-33 and was purified by cation exchange chromatography, followed by detection of its antibacterial activity in vitro and in vivo. The results showed that the total secreted protein concentration in fermentation supernatant was up to 2820 mg/L (29 °C) after 120-h induction in a 5-L fermentor. The yield of NZX reached up to 965 mg/L with a purity of 92.6%. The recombinant expressed NZX had a strong antimicrobial activity, high stability, and low toxicity. The minimal inhibitory concentrations (MICs) of NZX and ceftriaxone (CRO) against Gram-positive bacteria were 0.46 to 0.91 μM and 6.04 to 12.09 μM, respectively. The time-killing curves showed that S. hyicus NCTC10350 was killed completely by 2× and 4 × MIC of NZX within 24 h. NZX also exhibited the intracellular activity against S. hyicus in Hacat cells. After treatment with NZX (10 mg/kg) and CRO (60 mg/kg), the survival rates of mice were 100% and 83.3%, respectively. NZX inhibited the bacterial translocation, downregulated pro-inflammatory cytokines (TNF-α/IL-1β/IL-6), upregulated the anti-inflammatory cytokine (IL-10), and ameliorated multiple-organ injuries (the liver, spleen, lung, and kidney). This study provides evidence that the expressed NZX has the potential to become a powerful candidate as novel antimicrobial agents against S. hyicus infections.

Synergistic microbicidal effect of cationic antimicrobial peptides and teicoplanin against planktonic and biofilm-encased Staphylococcus aureus

Antibiotic resistance and biofilm formation are the main reasons for failure in treatment of bacterial infections. This study aimed to identify synergistic combinations of conventional antibiotics and novel synthetic antimicrobial and antibiofilm peptides (SAAPs) inspired by the structures of the natural human cationic peptides LL-37 and thrombocidin-1 (TC-1). The LL-37-inspired lead peptide SAAP-148 was combined with antibiotics of different classes against Staphylococcus aureus, and showed synergy with teicoplanin. Synergy with teicoplanin was also observed with LL-37, the LL-37-inspired SAAP-276 and the TC-1-inspired TC84. Interestingly, no synergy was observed against Staphylococcus epidermidis. Furthermore, teicoplanin combined with SAAP-148 or SAAP-276 showed strong interaction against S. aureus biofilms. The dltABCD operon and the mprF gene in S. aureus conferred resistance to LL-37, but SAAP-148 proved to be indifferently potent against wild-type, ΔdltA and ΔmprF S. aureus strains. When used alone, relatively high concentrations of both LL-37 and teicoplanin (30-120 µM and 4-32 mg/L, respectively) were required to kill S. aureus. Resistance to LL-37 in S. aureus was overcome by combined use of teicoplanin and LL-37. Thus, teicoplanin potentiates peptide LL-37, enhancing the efficacy of the innate defence, and combining the novel peptides with teicoplanin offers potential for enhanced efficacy of treatment of S. aureus infections, including biofilms.

In vitro and in vivo antibacterial effect of NZ2114 against Streptococcus suis type 2 infection in mice peritonitis models

NZ2114 is a promising candidate for therapeutic application owing to potent activity to gram-positive bacterium such as Streptococcus pneumoniae and Staphylococcus aureus. This work is the first report to describe the in vitro and in vivo antibacterial characteristics of NZ2114 against Streptococcus suis. It exhibited strong antimicrobial activity against S. suis type 2 strains CVCC 606, CVCC 3309, and CVCC 3928 at a low minimal inhibitory concentration (MIC) of 0.03–0.06 μM. The NZ2114 killed over 99.9% of tested S. suis CVCC 606 in Mueller–Hinton medium within 4 h when treated with 4 × MIC. It caused only less than 0.25% hemolytic activity in the concentration of 256 μg/ml. Additionally, NZ2114 exhibited potent in vivo activity to S. suis. All mice were survival when the dosage was low to 0.2 mg/kg. Over 99% of S. suis cells were killed within 4 h in blood, lung, liver and spleen with dosage of 10, 20, and 40 mg/kg in mice peritonitis models and no pathogen were detected after 24 h of treatment. Further, no pathological phenomenon in lung and low level of inflammatory cytokines in blood were detected. These results indicate that NZ2114 has the potential to be a new antimicrobial agent candidate for the clinical treatment of infection caused by S. suis type 2.

Design and pharmacodynamics of recombinant NZ2114 histidine mutants with improved activity against methicillin-resistant Staphylococcus aureus

NZ2114 is a promising candidate for therapeutic application owing to its potent activity to Staphylococcus aureus. Our objective was to identify NZ2114 derivatives with improved activity through substitution of His16 and His18 with residues Arginine and Lysine. Eight mutants were designed and expressed in Pichia pastoris X-33 via pPICZαA. Five of them exhibited strong antimicrobial activity against S. aureus at low minimal inhibitory concentrations (MICs) of 0.057-0.454 μM. Among them, H1, H2, and H3 showed ideal pharmacodynamic effects on methicillin-resistant S. aureus ATCC43300.  The total protein level of H1, H2, and H3 reached 1.70, 1.77 and 1.54 g/l at 120 h of induction in the 5-l fermenter, respectively. They killed over 99.9% of pathogens within 1.5 h at 2× and 4× MIC. The post antibiotic effect of H1, H2 and H3 to S. aureus ATCC43300 was 2.94, 1.75 and 1.55 h at 2× MIC, which was similar with their original peptide NZ2114 (1.43 h) and vancomycin (1.72 h). The fractional inhibitory concentration index (FICI) indicated indifferent effects between H1, H2, H3 and vancomycin, ampicillin, rifampicin. Additionally, they had low hemolysis and high stability in different environments (temperature, pH, proteases, and saline ions). All results indicate that H1, H2, and H3 can be produced in large-scale and have potential as therapeutic drugs against MRSA.

Antimicrobial peptides as an alternative to anti-tuberculosis drugs

Tuberculosis (TB) presently accounts for high global mortality and morbidity rates, despite the introduction four decades ago of the affordable and efficient four-drugs (isoniazid, rifampicin, pyrazinamide and ethambutol). Thus, a strong need exists for new drugs with special structures and uncommon modes of action to effectively overcome M. tuberculosis. Within this scope, antimicrobial peptides (AMPs), which are small, cationic and amphipathic peptides that comprise a section of the innate immune system, are currently the leading potential agents for the treatment of TB. Many studies have recently illustrated the capability of anti-mycobacterial peptides to disrupt the normal mycobacterial cell wall function through various modes, thereby interacting with the intracellular targets, as well as encompassing nucleic acids, enzymes and organelles. This review presents a wide array of antimicrobial activities, alongside the associated properties of the AMPs that could be utilized as potential agents in therapeutic tactics for TB treatment.

Fusion of plectasin derivative NZ2114 with hydrophilic random coil polypeptide: Recombinant production in Pichia pastoris and antimicrobial activity against clinical strain MRSA

One of the roadblocks towards the practical use of antimicrobial peptides for medical use is their relatively high cost when synthesized chemically. Effective recombinant production has only been successful in some cases, such as the previously reported production in Pichia pastoris of the antimicrobial plectasin derivative peptide NZ2114. The same production host has also been used extensively to produce so-called protein-polymers: sequences that consist of repetitions of simple amino acid motifs found in structural proteins such as collagen and elastin, and that can be designed to self-assemble in micelles, fibers and hydrogels. With the eventual goal of producing recombinant biomaterials such as antimicrobial protein polymer, we here explore the secreted production in Pichia pastoris of a fusion of NZ2114 with a hydrophilic random coil protein polymer CP4 . The intact NZ2114-CP4 fusion copolymer was produced with a yield of purified protein on the order of 1 g.L-1 supernatant. We find that purified NZ2114-CP4 has an activity against clinical strain MRSA, but very much lower than activity of chemically synthesized NZ2114. We conclude that possibly, the activity of NZ2114 is impaired by the C-terminal attachment to the protein polymer chain, but other reasons for the low activity cannot yet be excluded either. This article is protected by copyright. All rights reserved.

Host defense antimicrobial peptides as antibiotics: design and application strategies

This review deals with the design and application strategies of new antibiotics based on naturally occurring antimicrobial peptides (AMPs). The initial candidate can be designed based on three-dimensional structure or selected from a library of peptides from natural or laboratory sources followed by optimization via structure-activity relationship studies. There are also advanced application strategies such as induction of AMP expression from host cells by various factors (e.g., metals, amino acids, vitamin D and sunlight), the use of engineered probiotic bacteria to deliver peptides, the design of prodrug and peptide conjugates to improve specific targeting. In addition, combined uses of newly developed AMPs with existing antimicrobial agents may provide a practical avenue for effective management of antibiotic-resistant bacteria (superbugs), including biofilms. Finally, we highlight AMPs already in use or under clinical trials.

Fungal proteinaceous compounds with multiple biological activities

Fungi comprise organisms like molds, yeasts and mushrooms. They have been used as food or medicine for a long time. A large number of fungal proteins or peptides with diverse biological activities are considered as antibacterial, antifungal, antiviral and anticancer agents. They encompass proteases, ribosome inactivating proteins, defensins, hemolysins, lectins, laccases, ribonucleases, immunomodulatory proteins, and polysaccharopeptides. The target of the present review is to update the status of the various bioactivities of these fungal proteins and peptides and discuss their therapeutic potential.

Antimicrobial Approaches for Textiles: From Research to Market

The large surface area and ability to retain moisture of textile structures enable microorganisms' growth, which causes a range of undesirable effects, not only on the textile itself, but also on the user. Due to the public health awareness of the pathogenic effects on personal hygiene and associated health risks, over the last few years, intensive research has been promoted in order to minimize microbes' growth on textiles. Therefore, to impart an antimicrobial ability to textiles, different approaches have been studied, being mainly divided into the inclusion of antimicrobial agents in the textile polymeric fibers or their grafting onto the polymer surface. Regarding the antimicrobial agents, different types have been used, such as quaternary ammonium compounds, triclosan, metal salts, polybiguanides or even natural polymers. Any antimicrobial treatment performed on a textile, besides being efficient against microorganisms, must be non-toxic to the consumer and to the environment. This review mainly intends to provide an overview of antimicrobial agents and treatments that can be performed to produce antimicrobial textiles, using chemical or physical approaches, which are under development or already commercially available in the form of isolated agents or textile fibers or fabrics.