Eradication of Staphylococcus aureus Biofilm Infections Using Synthetic Antimicrobial Peptides

Antimicrobial spectrum against wound pathogens and cytotoxicity of star-arranged poly-l-lysine-based antimicrobial peptide polymers

Introduction. As growing numbers of patients are at higher risk of infection, novel topical broad-spectrum antimicrobials are urgently required for wound infection management. Robust pre-clinical studies should support the development of such novel antimicrobials.Gap statement. To date, evidence of robust investigation of the cytotoxicity and antimicrobial spectrum of activity of antimicrobial peptides (AMP)s is lacking in published literature. Using a more clinical lens, we address this gap in experimental approach, building on our experience with poly-l-lysine (PLL)-based AMP polymers.Aim. To evaluate the in vitro bactericidal activity and cytotoxicity of a PLL-based 16-armed star AMP polymer, designated 16-PLL10, as a novel candidate antimicrobial.Methods. Antimicrobial susceptibilities of clinical isolates and reference strains of ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter spp.) pathogens, to 16-PLL10 were investigated. Human erythrocyte haemolysis and keratinocyte viability assays were used to assess toxicity. Modifications were made to 16-PLL10 and re-evaluated for improvement.Results. Minimum bactericidal concentration of 16-PLL10 ranged from 1.25 µM to ≥25 µM. At 2.5 µM, 16-PLL10 was broadly bactericidal against ESKAPE strains/wound isolates. Log-reduction in colony forming units (c.f.u.) per millilitre after 1 h, ranged from 0.3 (E. cloacae) to 5.6 (K. pneumoniae). At bactericidal concentrations, 16-PLL10 was toxic to human keratinocyte and erythrocytes. Conjugates of 16-PLL10, Trifluoroacetylated (TFA)-16-PLL10, and Poly-ethylene glycol (PEG)ylated 16-PLL10, synthesised to address toxicity, only moderately reduced cytotoxicity and haemolysis.Conclusions. Due to poor selectivity indices, further development of 16-PLL10 is unlikely warranted. However, considering the unmet need for novel topical antimicrobials, the ease of AMP polymer synthesises/modification is attractive. To support more rational development, prioritising clinically relevant pathogens and human cells, to establish selective toxicity profiles in vitro, is critical. Further characterisation and discovery utilising artificial intelligence and computational screening approaches can accelerate future AMP nanomaterial development.

Biofilm formation in food industries: Challenges and control strategies for food safety

Various pathogens have the ability to grow on food matrices and instruments. This grow may reach to form biofilms. Bacterial biofilms are community of microorganisms embedded in extracellular polymeric substances (EPSs) containing lipids, DNA, proteins, and polysaccharides. These EPSs provide a tolerance and favorable living condition for microorganisms. Biofilm formations could not only contribute a risk for food safety but also have negative impacts on healthcare sector. Once biofilms form, they reveal resistances to traditional detergents and disinfectants, leading to cross-contamination. Inhibition of biofilms formation and abolition of mature biofilms is the main target for controlling of biofilm hazards in the food industry. Some novel eco-friendly technologies such as ultrasound, ultraviolet, cold plasma, magnetic nanoparticles, different chemicals additives as vitamins, D-amino acids, enzymes, antimicrobial peptides, and many other inhibitors provide a significant value on biofilm inhibition. These anti-biofilm agents represent promising tools for food industries and researchers to interfere with different phases of biofilms including adherence, quorum sensing molecules, and cell-to-cell communication. This perspective review highlights the biofilm formation mechanisms, issues associated with biofilms, environmental factors influencing bacterial biofilm development, and recent strategies employed to control biofilm-forming bacteria in the food industry. Further studies are still needed to explore the effects of biofilm regulation in food industries and exploit more regulation strategies for improving the quality and decreasing economic losses.

Exploring the skin microbiome in atopic dermatitis pathogenesis and disease modification

Inflammatory skin diseases such as atopic eczema (atopic dermatitis [AD]) affect children and adults globally. In AD, the skin barrier is impaired on multiple levels. Underlying factors include genetic, chemical, immunologic, and microbial components. Increased skin pH in AD is part of the altered microbial microenvironment that promotes overgrowth of the skin microbiome with Staphylococcus aureus. The secretion of virulence factors, such as toxins and proteases, by S aureus further aggravates the skin barrier deficiency and additionally disrupts the balance of an already skewed immune response. Skin commensal bacteria, however, can inhibit the growth and pathogenicity of S aureus through quorum sensing. Therefore, restoring a healthy skin microbiome could contribute to remission induction in AD. This review discusses direct and indirect approaches to targeting the skin microbiome through modulation of the skin pH; UV treatment; and use of prebiotics, probiotics, and postbiotics. Furthermore, exploratory techniques such as skin microbiome transplantation, ozone therapy, and phage therapy are discussed. Finally, we summarize the latest findings on disease and microbiome modification through targeted immunomodulatory systemic treatments and biologics. We believe that targeting the skin microbiome should be considered a crucial component of successful AD treatment in the future.

Correlation between catheter colonization of central venous catheters and clinical biochemical indicators: A retrospective analysis of the MIMIC‑IV database

BACKGROUND

Clinical studies have not fully assessed the potential impact of patients' biochemical indicators on the rate of positive for central venous catheter-tip microorganism culture (PCMC).

METHODS

Data were obtained from an online Medical Information Mart for Intensive Care IV database. Patients who were ≥18 years old and had central venous catheter-tip culture results without continuous renal replacement therapy were included in the study. A comparison of patient characteristics and their biochemical indicators was made between negative and positive culture results.

RESULTS

A total of 5,323 patients were included in the analysis, including 612 positive (PCMC group) and 4,711 negative culture results (negative for central venous catheter tip catheter-tip microorganism culture [NCMC] group). The only influence factor on PCMC in this study was the serum creatinine (Scr) (odds ratio: 1.312, 95% confidence interval: 1.084-1.590, P = .005), according to a binary logistic regression analysis. The cut-off value of Scr was 3.25 mg/dL. The prevalence of PCMC (27.1% vs 9.1%, P < .001) and Staphylococcus aureus (43.0% vs 18.6%, P < .001) for central venous catheter-tip culture results was much higher in patients with Scr ≥ 3.25 mg/dL than those Scr < 3.25 mg/dL.

CONCLUSIONS

We used the large dataset collected from Medical Information Mart for Intensive Care IV to show that patients with Scr ≥ 3.25 mg/dL had an increased risk for PCMC.

Unraveling Atopic Dermatitis: Insights into Pathophysiology, Therapeutic Advances, and Future Perspectives

Atopic dermatitis (AD) is an inflammatory skin condition that frequently develops before the onset of allergic rhinitis or asthma. More than 10% of children are affected by this serious skin condition, which is painful for the sufferers. Recent research has connected the environment, genetics, the skin barrier, drugs, psychological factors, and the immune system to the onset and severity of AD. The causes and consequences of AD and its cellular and molecular origins are reviewed in this paper. The exploration of interleukins and their influence on the immunological pathway in AD has been facilitated by using relevant biomarkers in clinical trials. This approach enables the identification of novel therapeutic modalities, fostering the potential for targeted translational research within the realm of personalized medicine. This review focuses on AD's pathophysiology and the ever-changing therapeutic landscape. Beyond the plethora of biologic medications in various stages of approval or development, a range of non-biologic targeted therapies, specifically small molecules, have emerged. These include Janus kinase (JAK) inhibitors like Baricitinib, Upadacitinib, and Abrocitinib, thus expanding the spectrum of therapeutic options. This review also addresses the latest clinical efficacy data and elucidates the scientific rationale behind each targeted treatment for atopic dermatitis.

The Study of Antistaphylococcal Potential of Omiganan and Retro-Omiganan Under Flow Conditions

Staphylococcus aureus is considered one of the leading pathogens responsible for infections in humans and animals. The heterogeneous nature of diseases caused by these bacteria is due to the occurrence of multiple strains, differentiated by several mechanisms of antibiotic resistance and virulence factors. One of these is the ability to form biofilm. Biofilm-associated bacteria exhibit a different phenotype that protects them from external factors such as the activity of immune system or antimicrobial substances. Moreover, it has been shown that the majority of persistent and recurrent infections are associated with the presence of the biofilm. Omiganan, an analog of indolicidin - antimicrobial peptide (AMP) derived from bovine neutrophil granules, was found to exhibit high antistaphylococcal and antibiofilm potential. Furthermore, its analog with a reversed sequence (retro-omiganan) was found to display enhanced activity against a variety of pathogens. Based on experience of our group, we found out that counterion exchange can improve the antistaphylococcal activity of AMPs. The aim of this study was to investigate the activity of both compounds against S. aureus biofilm under flow conditions. The advantage of this approach was that it offered the opportunity to form and characterize the biofilm under more controlled conditions. To do this, unique flow cells made of polydimethylsiloxane (PDMS) were developed. The activity against pre-formed biofilm as well as AMPs-treated bacteria was measured. Also, the incorporation of omiganan and retro-omiganan into the channels was conducted to learn whether or not it would inhibit the development of biofilm. The results of the microbiological tests ultimately confirmed the high potential of the omiganan and its retro-analog as well as the importance of counterion exchange in terms of antimicrobial examination. We found out that retro-omiganan trifluoroacetate had the highest biofilm inhibitory properties, however, acetates of both compounds exhibited the highest activity against planktonic and biofilm cultures. Moreover, the developed methodology of investigation under flow conditions allows the implementation of the studies under flow conditions to other compounds.

New Antimicrobial Strategies to Treat Multi-Drug Resistant Infections Caused by Gram-Negatives in Cystic Fibrosis

People with cystic fibrosis (CF) suffer from recurrent bacterial infections which induce inflammation, lung tissue damage and failure of the respiratory system. Prolonged exposure to combinatorial antibiotic therapies triggers the appearance of multi-drug resistant (MDR) bacteria. The development of alternative antimicrobial strategies may provide a way to mitigate antimicrobial resistance. Here we discuss different alternative approaches to the use of classic antibiotics: anti-virulence and anti-biofilm compounds which exert a low selective pressure; phage therapies that represent an alternative strategy with a high therapeutic potential; new methods helping antibiotics activity such as adjuvants; and antimicrobial peptides and nanoparticle formulations. Their mechanisms and in vitro and in vivo efficacy are described, in order to figure out a complete landscape of new alternative approaches to fight MDR Gram-negative CF pathogens.

Novel Antibacterial Agents SAAP-148 and Halicin Combat Gram-Negative Bacteria Colonizing Catheters

The antibiotic management of catheter-related infections (CRIs) often fails owing to the emergence of antimicrobial-resistant strains and/or biofilm/persister apparitions. Thus, we investigated the efficacy of two novel antimicrobial agents, i.e., the synthetic peptide SAAP-148 and the novel antibiotic halicin, against Gram-negative bacteria (GNB) colonizing catheters. The antibacterial, anti-biofilm, and anti-persister activities of both agents were evaluated against Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae strains. The enrolled strains were isolated from catheters and selected based on their resistance to at least three antibiotic classes and biofilm formation potential. Furthermore, the hemolysis and endotoxin neutralization abilities of these agents were explored. The bactericidal activity of both agents was reduced in urine and plasma as compared to buffered saline. In a dose-dependent manner, SAAP-148 and halicin reduced bacterial counts in 24 h preformed biofilms on silicone elastomer discs and eliminated persisters originating from antibiotic-exposed mature 7-day biofilms, with halicin being less effective than SAAP-148. Importantly, SAAP-148 and halicin acted synergistically on E. coli and K. pneumoniae biofilms but not on A. baumannii biofilms. The peptide, but not halicin, decreased the production of IL-12p40 upon exposure to UV-killed bacteria. This preliminary study showed that SAAP-148 and halicin alone/in combination are promising candidates to fight GNB colonizing catheters.

Recent advances in understanding the role of the skin microbiome in the treatment of atopic dermatitis

The skin is the largest organ in the human body, and histologically consists of the epidermis, dermis and subcutaneous tissue. Humans maintain a cooperative symbiotic relationship with their skin microbiota, a complex community of bacteria, fungi and viruses that live on the surface of the skin, and which act as a barrier to protect the body from the inside and outside. The skin is a 'habitat' and vast 'ecosystem' inhabited by countless microbes; as such, relationships have been forged through millions of years of coevolution. It is not surprising then that microbes are key participants in shaping and maintaining essential physiological processes. In addition to maintaining barrier function, the unique symbiotic microbiota that colonizes the skin increases the immune response and provides protection against pathogenic microbes. This review examines our current understanding of skin microbes in shaping and enhancing the skin barrier, as well as skin microbiome-host interactions and their roles in skin diseases, such as atopic dermatitis (AD). We also report on the current status of AD therapeutic drugs that target the skin microbiome, related research on current therapeutic strategies, and the limitations and future considerations of skin microbiome research. In particular, as a future strategy, we discuss the need for a skin-on-a-chip-based microphysiological system research model amenable to biomimetic in vitro studies and human skin equivalent models, including skin appendages.

Anti-methicillin-resistant Staphylococcus aureus and antibiofilm activity of new peptides produced by a Brevibacillus strain

Background

Methicillin-resistant Staphylococcus aureus (MRSA) is listed as a highly prioritized pathogen by the World Health Organization (WHO) to search for effective antimicrobial agents. Previously, we isolated a soil Brevibacillus sp. strain SPR19 from a botanical garden, which showed anti-MRSA activity. However, the active substances were still unknown.

Methods

The cell-free supernatant of this bacterium was subjected to salt precipitation, cation exchange, and reversed-phase chromatography. The antimicrobial activity of pure substances was determined by broth microdilution assay. The peptide sequences and secondary structures were characterized by tandem mass spectroscopy and circular dichroism (CD), respectively. The most active anti-MRSA peptide underwent a stability study, and its mechanism was determined through scanning electron microscopy, cell permeability assay, time-killing kinetics, and biofilm inhibition and eradication. Hemolysis was used to evaluate the peptide toxicity.

Results

The pure substances (BrSPR19-P1 to BrSPR19-P5) were identified as new peptides. Their minimum inhibition concentration (MIC) and minimum bactericidal concentration (MBC) against S. aureus and MRSA isolates ranged from 2.00 to 32.00 and 2.00 to 64.00 µg/mL, respectively. The sequence analysis of anti-MRSA peptides revealed a length ranging from 12 to 16 residues accompanied by an amphipathic structure. The physicochemical properties of peptides were predicted such as pI (4.25 to 10.18), net charge at pH 7.4 (-3 to +4), and hydrophobicity (0.12 to 0.96). The CD spectra revealed that all peptides in the water mainly contained random coil structures. The increased proportion of α-helix structure was observed in P2-P5 when incubated with SDS. P2 (NH2-MFLVVKVLKYVV-COOH) showed the highest antimicrobial activity and high stability under stressed conditions such as temperatures up to 100 °C, solution of pH 3 to 10, and proteolytic enzymes. P2 disrupted the cell membrane and caused bacteriolysis, in which its action was dependent on the incubation time and peptide concentration. Antibiofilm activity of P2 was determined by which the half-maximal inhibition of biofilm formation was observed at 2.92 and 4.84 µg/mL for S. aureus TISTR 517 and MRSA isolate 2468, respectively. Biofilm eradication of tested pathogens was found at the P2 concentration of 128 µg/mL. Furthermore, P2 hemolytic activity was less than 10% at concentrations up to 64 µg/mL, which reflected the hemolysis index thresholds of 32.

Conclusion

Five novel anti-MRSA peptides were identified from SPR19. P2 was the most active peptide and was demonstrated to cause membrane disruption and cell lysis. The P2 activity was dependent on the peptide concentration and exposure time. This peptide had antibiofilm activity against tested pathogens and was compatible with human erythrocytes, supporting its potential use as an anti-MRSA agent in this post-antibiotic era.

Fibrinolytic and antibiotic treatment of prosthetic vascular graft infections in a novel rat model

OBJECTIVES

We developed a rat model of prosthetic vascular graft infection to assess, whether the fibrinolytic tissue plasminogen activator (tPA) could increase the efficacy of antibiotic therapy.

MATERIALS AND METHODS

Rats were implanted a polyethylene graft in the common carotid artery, pre-inoculated with approx. 6 log10 colony forming units (CFU) of methicillin resistant Staphylococcus aureus. Ten days after surgery, rats were randomized to either: 0.9% NaCl (n = 8), vancomycin (n = 8), vancomycin + tPA (n = 8), vancomycin + rifampicin (n = 18) or vancomycin + rifampicin + tPA (n = 18). Treatment duration was seven days. Approximately 36 hours after the end of treatment, the rats were euthanized, and grafts and organs were harvested for CFU enumeration.

RESULTS

All animals in the control group had significantly higher CFU at the time of euthanization compared to bacterial load found on the grafts prior to inoculation (6.45 vs. 4.36 mean log10 CFU/mL, p = 0.0011), and both the procedure and infection were well tolerated. Vancomycin and rifampicin treatment were superior to monotherapy with vancomycin, as it lead to a marked decrease in median bacterial load on the grafts (3.50 vs. 6.56 log10 CFU/mL, p = 0.0016). The addition of tPA to vancomycin and rifampicin combination treatment did not show a further decrease in bacterial load (4.078 vs. 3.50 log10 CFU/mL, p = 0.26). The cure rate was 16% in the vancomycin + rifampicin group vs. 37.5% cure rate in the vancomycin + rifampicin + tPA group. Whilst interesting, this trend was not significant at our sample size (p = 0.24).

CONCLUSION

We developed the first functional model of an arterial prosthetic vascular graft infection in rats. Antibiotic combination therapy with vancomycin and rifampicin was superior to vancomycin monotherapy, and the addition of tPA did not significantly reduce bacterial load, nor significantly increase cure rate.

Green Antimicrobials as Therapeutic Agents for Diabetic Foot Ulcers

Diabetic foot ulcers (DFU) are one of the most serious and devastating complications of diabetes and account for a significant decrease in quality of life and costly healthcare expenses worldwide. This condition affects around 15% of diabetic patients and is one of the leading causes of lower limb amputations. DFUs generally present poor clinical outcomes, mainly due to the impaired healing process and the elevated risk of microbial infections which leads to tissue damage. Nowadays, antimicrobial resistance poses a rising threat to global health, thus hampering DFU treatment and care. Faced with this reality, it is pivotal to find greener and less environmentally impactful alternatives for fighting these resistant microbes. Antimicrobial peptides are small molecules that play a crucial role in the innate immune system of the host and can be found in nature. Some of these molecules have shown broad-spectrum antimicrobial properties and wound-healing activity, making them good potential therapeutic compounds to treat DFUs. This review aims to describe antimicrobial peptides derived from green, eco-friendly processes that can be used as potential therapeutic compounds to treat DFUs, thereby granting a better quality of life to patients and their families while protecting our fundamental bio-resources.

'Targeting' the search: An upgraded structural and functional repository of antimicrobial peptides for biofilm studies (B-AMP v2.0) with a focus on biofilm protein targets

Bacterial biofilms, often as multispecies communities, are recalcitrant to conventional antibiotics, making the treatment of biofilm infections a challenge. There is a push towards developing novel anti-biofilm approaches, such as antimicrobial peptides (AMPs), with activity against specific biofilm targets. In previous work, we developed Biofilm-AMP, a structural and functional repository of AMPs for biofilm studies (B-AMP v1.0) with more than 5000 structural models of AMPs and a vast library of AMP annotations to existing biofilm literature. In this study, we present an upgraded version of B-AMP, with a focus on existing and novel bacterial biofilm targets. B-AMP v2.0 hosts a curated collection of 2502 biofilm protein targets across 473 bacterial species, with structural protein models and functional annotations from PDB, UniProt, and PubMed databases. The biofilm targets can be searched for using the name of the source organism, and function and type of protein, and results include designated Target IDs (unique to B-AMP v2.0), UniProt IDs, 3D predicted protein structures, PDBQT files, pre-defined protein functions, and relevant scientific literature. To present an example of the combined applicability of both, the AMP and biofilm target libraries in the repository, we present two case studies. In the first case study, we expand an in silico pipeline to evaluate AMPs against a single biofilm target in the multidrug resistant, bacterial pathogen Corynebacterium striatum, using 3D protein-peptide docking models from previous work and Molecular Dynamics simulations (~1.2µs). In the second case study, we build an in silico pipeline to identify candidate AMPs (using AMPs with both anti-Gram positive and anti-Gram negative activity) against two biofilm targets with a common functional annotation in Pseudomonas aeruginosa and Staphylococcus aureus, widely-encountered bacterial co-pathogens. With its enhanced structural and functional capabilities, B-AMP v2.0 serves as a comprehensive resource for AMP investigations related to biofilm studies. B-AMP v2.0 is freely available at https://b-amp.karishmakaushiklab.com and will be regularly updated with structural models of AMPs and biofilm targets, as well as 3D protein-peptide interaction models for key biofilm-forming pathogens.

Biofilms: Formation, Research Models, Potential Targets, and Methods for Prevention and Treatment

Due to the continuous rise in biofilm-related infections, biofilms seriously threaten human health. The formation of biofilms makes conventional antibiotics ineffective and dampens immune clearance. Therefore, it is important to understand the mechanisms of biofilm formation and develop novel strategies to treat biofilms more effectively. This review article begins with an introduction to biofilm formation in various clinical scenarios and their corresponding therapy. Established biofilm models used in research are then summarized. The potential targets which may assist in the development of new strategies for combating biofilms are further discussed. The novel technologies developed recently for the prevention and treatment of biofilms including antimicrobial surface coatings, physical removal of biofilms, development of new antimicrobial molecules, and delivery of antimicrobial agents are subsequently presented. Finally, directions for future studies are pointed out.

Recent Advances in the Control of Clinically Important Biofilms

Biofilms are complex structures formed by bacteria, fungi, or even viruses on biotic and abiotic surfaces, and they can be found in almost any part of the human body. The prevalence of biofilm-associated diseases has increased in recent years, mainly because of the frequent use of indwelling medical devices that create opportunities for clinically important bacteria and fungi to form biofilms either on the device or on the neighboring tissues. As a result of their resistance to antibiotics and host immunity factors, biofilms have been associated with the development or persistence of several clinically important diseases. The inability to completely eradicate biofilms drastically increases the burden of disease on both the patient and the healthcare system. Therefore, it is crucial to develop innovative ways to tackle the growth and development of biofilms. This review focuses on dental- and implant-associated biofilm infections, their prevalence in humans, and potential therapeutic intervention strategies, including the recent advances in pharmacology and biomedical engineering. It lists current strategies used to control the formation of clinically important biofilms, including novel antibiotics and their carriers, antiseptics and disinfectants, small molecule anti-biofilm agents, surface treatment strategies, and nanostructure functionalization, as well as multifunctional coatings particularly suitable for providing antibacterial effects to the surface of implants, to treat either dental- or implant-related bacterial infections.

Current treatments for biofilm-associated periprosthetic joint infection and new potential strategies

Periprosthetic joint infection (PJI) remains a devastating complication after total joint arthroplasty. Bacteria involved in these infections are notorious for adhering to foreign implanted surfaces and generating a biofilm matrix. These biofilms protect the bacteria from antibiotic treatment and the immune system making eradication difficult. Current treatment strategies including debridement, antibiotics, and implant retention, and one- and two-stage revisions still present a relatively high overall failure rate. One of the main shortcomings that has been associated with this high failure rate is the lack of a robust approach to treating bacterial biofilm. Therefore, in this review, we will highlight new strategies that have the potential to combat PJI by targeting biofilm integrity, therefore giving antibiotics and the immune system access to the internal network of the biofilm structure. This combination antibiofilm/antibiotic therapy may be a new strategy for PJI treatment while promoting implant retention.

The Influence of Short Motifs on the Anticancer Activity of HB43 Peptide

Despite the remarkable similarity in amino acid composition, many anticancer peptides (ACPs) display significant differences in terms of activity. This strongly suggests that particular relative dispositions of amino acids (motifs) play a role in the interaction with their biological target, which is often the cell membrane. To better verify this hypothesis, we intentionally modify HB43, an ACP active against a wide variety of cancers. Sequence alignment of related ACPs by ADAPTABLE web server highlighted the conserved motifs that could be at the origin of the activity. In this study, we show that changing the order of amino acids in such motifs results in a significant loss of activity against colon and breast cancer cell lines. On the contrary, amino acid substitution in key motifs may reinforce or weaken the activity, even when the alteration does not perturb the amphipathicity of the helix formed by HB43 on liposomes mimicking their surface. NMR and MD simulations with different membrane models (micelles, bicelles, and vesicles) indicate that the activity reflects the insertion capability in cancer-mimicking serine-exposing membranes, supported by the insertion of N-terminal phenylalanine in the FAK motif and the anchoring to the carboxylate of phosphatidylserine by means of arginine side chains.

Molecular Aspects of the Interaction with Gram-Negative and Gram-Positive Bacteria of Hydrothermal Carbon Nanoparticles Associated with Bac8c2,5Leu Antimicrobial Peptide

Antimicrobial peptides (AMPs) are widely studied as therapeutic agents due to their broad-spectrum efficacy against infections. However, their clinical use is hampered by the low in vivo bioavailability and systemic toxicity. Such limitations might be overcome by using appropriate drug delivery systems. Here, the preparation of a drug delivery system (DDS) by physical conjugation of an arginine-rich peptide and hydrothermal carbon nanoparticles (CNPs) has been explored, and its antimicrobial efficacy against Eschericia coli (E. coli) and Staphylococcus aureus investigated in comparison with the unloaded carrier and the free peptide. The mechanism of interaction between CNPs and the bacteria was investigated by scanning electron microscopy and a combined dielectrophoresis-Raman spectroscopy method for real-time analysis. In view of a possible systemic administration, the effect of proteins on the stability of the DDS was investigated by using albumin as a model protein. The peptide was bounded electrostatically to the CNPs surface, establishing an equilibrium modulated by pH and albumin. The DDS exhibited antimicrobial activity toward the two bacterial strains, albeit lower as compared to the free peptide. The decrease in effectiveness toward E. coli was likely due to the rapid formation of a particle-induced extracellular matrix. The present results are relevant for the future development of hydrothermal CNPs as drug delivery agents of AMPs.

Antimicrobial Peptides as an Alternative for the Eradication of Bacterial Biofilms of Multi-Drug Resistant Bacteria

Bacterial resistance is an emergency public health problem worldwide, compounded by the ability of bacteria to form biofilms, mainly in seriously ill hospitalized patients. The World Health Organization has published a list of priority bacteria that should be studied and, in turn, has encouraged the development of new drugs. Herein, we explain the importance of studying new molecules such as antimicrobial peptides (AMPs) with potential against multi-drug resistant (MDR) and extensively drug-resistant (XDR) bacteria and focus on the inhibition of biofilm formation. This review describes the main causes of antimicrobial resistance and biofilm formation, as well as the main and potential AMP applications against these bacteria. Our results suggest that the new biomacromolecules to be discovered and studied should focus on this group of dangerous and highly infectious bacteria. Alternative molecules such as AMPs could contribute to eradicating biofilm proliferation by MDR/XDR bacteria; this is a challenging undertaking with promising prospects.

Antimicrobial peptides properties beyond growth inhibition and bacterial killing

Antimicrobial peptides (AMPs) are versatile molecules with broad antimicrobial activity produced by representatives of the three domains of life. Also, there are derivatives of AMPs and artificial short peptides that can inhibit microbial growth. Beyond killing microbes, AMPs at grow sub-inhibitory concentrations also exhibit anti-virulence activity against critical pathogenic bacteria, including ESKAPE pathogens. Anti-virulence therapies are an alternative to antibiotics since they do not directly affect viability and growth, and they are considered less likely to generate resistance. Bacterial biofilms significantly increase antibiotic resistance and are linked to establishing chronic infections. Various AMPs can kill biofilm cells and eradicate infections in animal models. However, some can inhibit biofilm formation and promote dispersal at sub-growth inhibitory concentrations. These examples are discussed here, along with those of peptides that inhibit the expression of traits controlled by quorum sensing, such as the production of exoproteases, phenazines, surfactants, toxins, among others. In addition, specific targets that are determinants of virulence include secretion systems (type II, III, and VI) responsible for releasing effector proteins toxic to eukaryotic cells. This review summarizes the current knowledge on the anti-virulence properties of AMPs and the future directions of their research.

Modified poly(L-lysine)-based structures as novel antimicrobials for diabetic foot infections, an in-vitro study

Background: Wound infections occur as sequelae to skin trauma and cause significant hospitalizations, morbidity and mortality. Skin traumas arise more frequently in those with diabetes or cardiovascular disease and in these settings, may be chronic with poorer outcomes including lower limb amputation. Treatment of chronic wound infection is challenging due to antibiotic resistance and biofilm formation by bacteria including S. aureus and P. aeruginosa, which are among the most frequent causative pathogens. Managing these challenging infections requires new molecules and modalities. Methods: We evaluated antimicrobial and anti-biofilm activity of star-shaped poly(L-lysine) (PLL) polymers against S. aureus and P. aeruginosa strains and clinical isolates recovered from wounds including diabetic foot wounds (DFW) in a Dublin Hospital in 2019. A star-shaped PLL polypeptide series, specifically G2(8)PLL ₂₀, G3(16)PLL ₁₀, G4(32)PLL ₅ with variation in polypeptide chain length and arm-multiplicity, were compared to a linear peptide, PLL ₁₆₀ with equivalent number of lysine residues. Results: All PLLs, including the linear polypeptide, were bactericidal at 1μM against S. aureus 25923 and P. aeruginosa PAO1, with log reduction in colony forming units/ml between 2.7-3.6. PLL ₁₆₀ demonstrated similar killing potency against 20 S. aureus and five P. aeruginosa clinical isolates from DFW, mean log reductions: 3.04 ± 0.16 and 3.96 ± 0.82 respectively after 1 hour incubation. Potent anti-biofilm activity was demonstrated against S. aureus 25923 but for clinical isolates, low to moderate loss of biofilm viability was shown using PLL ₁₆₀ and G3(16)PLL ₁₀ at 50 μM ( S. aureus) and 200 μM ( P. aeruginosa) with high inter-isolate variability . In the star-shaped architecture, antimicrobial activity was retained with incorporation of 5-mer hydrophobic amino-acid modifications to the arms of the polypeptides (series G3(16)PLL ₂₀-coPLT ₅, G3(16)PLL ₂₀-coPLI ₅, G3(16)PLL ₂₀-coPLP ₅). Conclusion: These polypeptides offer structural flexibility for clinical applications and have potential for further development, particularly in the setting of diabetic foot and other chronic wound infections.

Skin microbiome of atopic dermatitis

The skin microbiome is a key component of pathogenesis in atopic dermatitis (AD). The skin of AD patients is characterized by microbial dysbiosis, with a reduction of microbial diversity and overrepresentation of pathogenic Staphylococcus aureus (S. aureus). Recent exciting studies have elucidated an importance of establishing an appropriate immune response to microbes in early life and uncovered the new mechanisms of microbial community dynamics in modulating our skin microbiome. Several microbes are associated with AD pathogenesis, with proposed pathogenic effects from S. aureus and Malassezia. The complex relationships between microbes within the skin microbiome consortia includes various species, such as Staphylococcal, Roseomonas and Cutibacterium strains, that can inhibit S. aureus and are potential probiotics for AD skin. Numerous microbes are now also reported to modulate host response via communication with keratinocytes, specialized immune cells and adipocytes to improve skin health and barrier function. This increased understanding of skin microbiota bioactives has led to new biotherapeutic approaches that target the skin surface microenvironment for AD treatment.

The impact of phosphatidylserine exposure on cancer cell membranes on the activity of the anticancer peptide HB43

HB43 (FAKLLAKLAKKLL) is a synthetic peptide active against cell lines derived from breast, colon, melanoma, lung, prostate, and cervical cancers. Despite its remarkable spectrum of activity, the mechanism of action at the molecular level has never been investigated, preventing further optimization of its selectivity. The alternation of charged and hydrophobic residues suggests amphipathicity, but the formation of alpha-helical structure seems discouraged by its short length and the large number of positively charged residues. Using different biophysical and in silico approaches we show that HB43 is completely unstructured in solution but assumes alpha-helical conformation in the presence of DPC micelles and liposomes exposing phosphatidylserine (PS) used as mimics of cancer cell membranes. Membrane permeabilization assays demonstrate that the interaction leads to the preferential destabilization of PS-containing vesicles with respect to PC-containing ones, here used as noncancerous cell mimics. ssNMR reveals that HB43 is able to fluidify the internal structure of cancer-cell mimicking liposomes while MD simulations show its internalization in such bilayers. This is achieved by the formation of specific interactions between the lysine side chains and the carboxylate group of phosphatidylserine and/or the phosphate oxygen atoms of targeted phospholipids, which could catalyze the formation of the alpha helix required for internalization. With the aim of better understanding the peptide biocompatibility and the additional antibacterial activity, the interaction with noncancerous cell mimicking liposomes exposing phosphatidylcholine (PC) and bacterial mimicking bilayers exposing phosphatidylglycerol (PG) is also described.

Atopic dermatitis: an expanding therapeutic pipeline for a complex disease

Atopic dermatitis (AD) is a common chronic inflammatory skin disease with a complex pathophysiology that underlies a wide spectrum of clinical phenotypes. AD remains challenging to treat owing to the limited response to available therapies. However, recent advances in understanding of disease mechanisms have led to the discovery of novel potential therapeutic targets and drug candidates. In addition to regulatory approval for the IL-4Ra inhibitor dupilumab, the anti-IL-13 inhibitor tralokinumab and the JAK1/2 inhibitor baricitinib in Europe, there are now more than 70 new compounds in development. This Review assesses the various strategies and novel agents currently being investigated for AD and highlights the potential for a precision medicine approach to enable prevention and more effective long-term control of this complex disease.

Recent advances in understanding of the complex phenotype and mechanisms underlying atopic dermatitis (AD) have revealed multiple new potential targets for pharmacological intervention. Here, Bieber reviews therapeutic strategies and assesses the expanding pipeline for the therapy of AD, highlighting the potential for a precision medicine approach to the management of this complex disorder.

The Propensity to Form Biofilm in vitro by Staphylococcus aureus Strains Isolated from the Anterior Nares of Patients with Atopic Dermatitis: Clinical Associations

BACKGROUND

Atopic dermatitis is a chronic inflammatory dermatosis with complex pathogenesis. The skin microbiome in atopic dermatitis is dominated by Staphylococcus aureus which shows the ability to produce biofilm.

OBJECTIVES

The aim of this work was to assess the influence of S. aureus biofilm on the course of atopic dermatitis.

METHODS

Disease severity was evaluated based on the SCORAD index in 56 adult patients with atopic dermatitis. Microtiter plate assay of the propensity to form biofilm was performed on S. aureus strains isolated from the anterior nares, lesional skin, and nonlesional skin. Microbiological results were correlated to the clinical parameters and total IgE concentration.

RESULTS

Biofilm-producing strains of S. aureus were identified in 76.3% (29/38) and 79.1% (34/43) of samples from the anterior nares and lesional skin, respectively (p > 0.05), and in 48.5% (16/33) of samples from nonlesional skin (p < 0.03). Patients colonized by biofilm-producing strains of S. aureus within the anterior nares showed statistically higher mean values of total and objective SCORAD and its components (extent, dryness), and of the largest extent of skin lesions during the flares in the last year when compared to patients colonized by non-biofilm-producing strains. Carriage of biofilm-producing S. aureus on lesional skin was associated with higher mean values of the extent of skin lesions during stable periods of the disease.

CONCLUSIONS

The results of this study may suggest a relationship between the production of biofilm by S. aureus strains colonizing the anterior nares and the course of atopic dermatitis. Biofilm seems crucial for dispersal and persistent colonization of large areas of the skin by this pathogen. Destruction of S. aureus biofilm could positively affect the course of atopic dermatitis.

Innate Inspiration: Antifungal Peptides and Other Immunotherapeutics From the Host Immune Response

The purpose of this review is to describe antifungal therapeutic candidates in preclinical and clinical development derived from, or directly influenced by, the immune system, with a specific focus on antimicrobial peptides (AMP). Although the focus of this review is AMP with direct antimicrobial effects on fungi, we will also discuss compounds with direct antifungal activity, including monoclonal antibodies (mAb), as well as immunomodulatory molecules that can enhance the immune response to fungal infection, including immunomodulatory AMP, vaccines, checkpoint inhibitors, interferon and colony stimulating factors as well as immune cell therapies. The focus of this manuscript will be a non-exhaustive review of antifungal compounds in preclinical and clinical development that are based on the principles of immunology and the authors acknowledge the incredible amount of in vitro and in vivo work that has been conducted to develop such therapeutic candidates.

Design of a Sea Snake Antimicrobial Peptide Derivative with Therapeutic Potential against Drug-Resistant Bacterial Infection

Infections caused by drug-resistant pathogens are a worldwide challenge for public health. Antimicrobial peptides (AMPs) are regarded as promising antibiotic alternatives for the treatment of drug-resistant infections. In the present study, a series of small peptides were designed based on our previously reported sea snake AMP Hc-CATH. From them, the lead peptide HC1-D2, a truncated peptide entirely substituted by d-amino acids, was selected. HC1-D2 exhibited significantly improved stability and antibiofilm and anti-inflammatory activities. Meanwhile, HC1-D2 retained potent, broad-spectrum, and rapid antimicrobial properties against bacteria and fungi, especially drug-resistant bacteria. Moreover, HC1-D2 showed low propensity to induce bacterial resistance and low cytotoxicity and hemolytic activity. Notably, HC1-D2 showed potent in vivo anti-infective ability in mouse peritonitis models infected by both standard and drug-resistant bacteria. It significantly decreased the bacterial counts in the abdominal cavity and spleen of mice and apparently increased the survival rates of the mice. Acting through the MAPKs inflammatory pathway, HC1-D2 selectively induced the production of chemokine and the subsequent immune cell recruitment to the infection site, while inhibiting the production of pro-inflammatory cytokines with undesirable toxicities. These much improved properties make HC1-D2 a promising candidate for the development of novel peptide anti-infective agents against drug-resistant infections.

Cathelicidin Host Defense Peptides and Inflammatory Signaling: Striking a Balance

Host-defense peptides (HDPs) are vital components of innate immunity in all vertebrates. While their antibacterial activity toward bacterial cells was the original focus for research, their ability to modulate immune and inflammatory processes has emerged as one of their major functions in the host and as a promising approach from which to develop novel therapeutics targeting inflammation and innate immunity. In this review, with particular emphasis on the cathelicidin family of peptides, the roles of natural HDPs are examined in managing immune activation, cellular recruitment, cytokine responses, and inflammation in response to infection, as well as their contribution(s) to various inflammatory disorders and autoimmune diseases. Furthermore, we discuss current efforts to develop synthetic HDPs as therapeutics aimed at restoring balance to immune responses that are dysregulated and contribute to disease pathologies.

Non-antibiotic antimicrobial agents to combat biofilm-forming bacteria

Biofilms can be produced by multiple species or by a single strain of bacteria. The biofilm state enhances the resistance of the resident microorganisms to antimicrobial agents by producing extracellular polymeric substances. Typically, antibiotics are used to stop the growth of bacteria, but emerging resistance has limited their effectiveness. Bacteria in biofilms are less susceptible to antibiotics compared with their free-floating state, as biofilms impair antibiotic penetration. To obviate this challenge, non-antibiotic antimicrobial agents are needed. This review describes two classes of these agents, namely antimicrobial nanoparticles and antimicrobial peptides. Applications of these antimicrobials in the food industry and medical applications are discussed, and the directions for future research are highlighted.

Synergistic combinations of antimicrobial peptides against biofilms of methicillin-resistant Staphylococcus aureus (MRSA) on polystyrene and medical devices

OBJECTIVES

Antimicrobial research is being focused to look for more effective therapeutics against antibiotic-resistant infections such as those caused by methicillin-resistant Staphylococcus aureus (MRSA). In this regard, antimicrobial peptides (AMPs) appear to be a promising solution. The aim of the present study was to investigate the potential activity of temporin A, citropin 1.1, CA(1-7)M(2-9)NH₂ and Pal-KGK-NH₂ in synergistic activity against MRSA biofilms developed on polystyrene surface (PSS) and central venous catheter (CVC).

METHODS

The study was subdivided into distinct phases to assess the ability of AMPs to inhibit biofilm formation, to identify possible synergy between AMPs, and to eradicate preformed biofilms on PSS and CVC using AMPs alone or in combination.

RESULTS

Activity of the AMPs was particularly evident in the inhibition of biofilm formation on PSS and CVC, whilst the eradication of preformed biofilms was more difficult and was reached only after 24h of contact. The synergistic activity of AMP combinations, selected by their fractional inhibitory concentration index (FICI), led to an improvement in the performance of all of the molecules in the removal of different biofilms.

CONCLUSION

Overall, AMPs could represent the next generation of antimicrobial agents for a prophylactic or therapeutic tool to control biofilms of antibiotic-resistant bacteria and/or biofilm-associated infections on different medical devices.

Replacement of l-Amino Acids by d-Amino Acids in the Antimicrobial Peptide Ranalexin and Its Consequences for Antimicrobial Activity and Biodistribution

Infections caused by multidrug-resistant bacteria are a global emerging problem. New antibiotics that rely on innovative modes of action are urgently needed. Ranalexin is a potent antimicrobial peptide (AMP) produced in the skin of the American bullfrog Rana catesbeiana. Despite strong antimicrobial activity against Gram-positive bacteria, ranalexin shows disadvantages such as poor pharmacokinetics. To tackle these problems, a ranalexin derivative consisting exclusively of d-amino acids (named danalexin) was synthesized and compared to the original ranalexin for its antimicrobial potential and its biodistribution properties in a rat model. Danalexin showed improved biodistribution with an extended retention in the organisms of Wistar rats when compared to ranalexin. While ranalexin is rapidly cleared from the body, danalexin is retained primarily in the kidneys. Remarkably, both peptides showed strong antimicrobial activity against Gram-positive bacteria and Gram-negative bacteria of the genus Acinetobacter with minimum inhibitory concentrations (MICs) between 4 and 16 mg/L (1.9–7.6 µM). Moreover, both peptides showed lower antimicrobial activities with MICs ≥32 mg/L (≥15.2 µM) against further Gram-negative bacteria. The preservation of antimicrobial activity proves that the configuration of the amino acids does not affect the anticipated mechanism of action, namely pore formation.

Biological characterization of omw1 and omw2: antimicrobial peptides derived from omwaprin

Two cationic antimicrobial peptides (AMP) were designed based on the snake venom peptide, omwaprin, hypothesized to be shorter, cost effective and potent. Omw1 and omw2 demonstrated significant broad-spectrum antimicrobial activity against standard and clinical strains at a MIC ranging from 15.625 to 250 µg/ml for omw1 and from 31.3 to 500 µg/ml for omw2. Time-kill kinetics revealed that omw1 caused complete lysis of E. coli ATCC 25922 at 1× MIC and S. aureus ATCC 25923 at 2× MIC after 40 and 60 min of incubation, respectively. Membranolytic activity of the peptides was assessed by propidium iodide stain, where red fluorescence was observed in cells treated with the peptides compared to untreated cells. Notable morphological changes were observed in the microbes treated with peptides, as revealed by scanning electron micrographs. Omw1 and omw2 were also potent to inhibit the formation as well as dispersal of matured biofilms at 1/2× MIC against clinical strain, C. albicans. Further, minimal hemolytic activity demonstrated by both the peptides at microbicidal concentration against human erythrocytes proves that the designed peptides were less toxic and potent antimicrobial agents which could be considered for further studies with animal models to affirm its efficiency.

Biofilms: Novel Strategies Based on Antimicrobial Peptides

The problem of drug resistance is very worrying and ever increasing. Resistance is due not only to the reckless use of antibiotics but also to the fact that pathogens are able to adapt to different conditions and develop self-defense mechanisms such as living in biofilms; altogether these issues make the search for alternative drugs a real challenge. Antimicrobial peptides appear as promising alternatives but they have disadvantages that do not make them easily applicable in the medical field; thus many researches look for solutions to overcome the disadvantages and ensure that the advantages can be exploited. This review describes the biofilm characteristics and identifies the key features that antimicrobial peptides should have. Recalcitrant bacterial infections caused by the most obstinate bacterial species should be treated with a strategy to combine conventional peptides functionalized with nano-tools. This approach could effectively disrupt high density infections caused by biofilms. Moreover, the importance of using in vivo non mammalian models for biofilm studies is described. In particular, here we analyze the use of amphibians as a model to substitute the rodent model.

Antibiofilm activity and modes of action of a novel β-sheet peptide against multidrug-resistant Salmonella enterica

S. enterica is an important foodborne pathogen worldwide. As some strains can form biofilms which may offer protection against antimicrobials, it is of interest to explore ways to prevent biofilm formation by S. enterica. In this study, we engineered a short β-sheet peptide WK2 (WKWKCTKSGCKWKW-NH₂) and examined its antimicrobial and anti-biofilm activities against various S. enterica strains, including the multidrug-resistant S. Typhimurium DT104. WK2 displayed bacteriostatic activity with a geometric mean (GM) minimum inhibitory concentration (MIC) of 4.17 μg/mL, and bactericidal activity, with a GM lethal concentration (LC) of 7.51 μg/mL. Crystal violet staining and fluorescence measurements demonstrated that WK2 inhibited S. Typhimurium DT104 biofilm formation at 0.5 μg/mL and killed the sessile cells in biofilms at 8 μg/mL. Real-time polymerase chain reaction (qPCR) and microscopic observation revealed that the anti-biofilm activity of WK2 likely arises through the formation of complexes with bacterial DNA, inhibition of surface organelle biosynthesis and interference with autoinducer-2 (AI-2)-mediated quorum sensing (QS). Therefore, WK2 is a promising antimicrobial agent for the prevention and control of biofilms produced by multidrug-resistant S. enterica.

Antimicrobial random peptide cocktails: a new approach to fight pathogenic bacteria

Antibiotic resistance in bacteria has become a serious threat to public health, and therefore there is an urgent need to develop new classes of antimicrobial agents. Nowadays, natural antimicrobial peptides (AMPs) and their synthetic derivatives are considered as promising alternatives to traditional antibiotics. The broad molecular diversity of AMPs, in terms of sequences and structures, suggests that their activity does not depend on specific features of amino acid sequence or peptide conformation. We therefore selected two common properties of AMPs, (high percentage of hydrophobic and cationic amino acids), to develop a novel approach to synthesize random antimicrobial peptide mixtures (RPMs). Instead of incorporating a single amino acid at each coupling step, a mixture of hydrophobic and cationic amino acids in a defined proportion is coupled. This results in a mixture that contains up to 2n sequences, where n is the number of the coupling step, of random peptides with a defined composition, stereochemistry, and controlled chain length. We have discovered that RPMs of hydrophobic and cationic α-amino acids, such as phenylalanine and lysine, display strong and broad antimicrobial activity towards Gram-negative, Gram-positive, clinically isolated antibiotic resistant "superbugs", and several plant pathogenic bacteria. This review summarizes our efforts to explore the mode of action of RPMs and their potential as bioactive agents for multiple applications, including the prevention of biofilm formation and degradation of mature biofilm (related to human health), reduction of disease severity in plant bacterial disease models (related to crop protection), and inhibition of bacterial growth in milk (related to food preservation). All our findings illustrate the effectiveness of RPMs and their great potential for various applications.

Staphylococcus aureus: an underestimated factor in the pathogenesis of atopic dermatitis?

Atopic dermatitis is a common, recurrent pruritic dermatosis with a complex pathogenesis. It has been associated with disordered patterns of immunological response and impaired epithelial barrier integrity. These features predispose the patients to robust colonization of skin lesions by Staphylococcus aureus. Virulence factors of S. aureus (e.g. superantigens, α- and δ-toxin, protein A) have been shown to exacerbate and perpetuate the course of atopic dermatitis. Novel therapeutic options with potential for restoring natural microbiome composition are being elaborated and may enter clinical practice in the future.

Cytotoxic Potential of the Novel Horseshoe Crab Peptide Polyphemusin III

Biological activity of the new antimicrobial peptide polyphemusin III from the horseshoe crab Limulus polyphemus was examined against bacterial strains and human cancer, transformed, and normal cell cultures. Polyphemusin III has the amino acid sequence RRGCFRVCYRGFCFQRCR and is homologous to other β-hairpin peptides from the horseshoe crab. Antimicrobial activity of the peptide was evaluated and MIC (minimal inhibitory concentration) values were determined. IC₅₀ (half-maximal inhibitory concentration) values measured toward human cells revealed that polyphemusin III showed a potent cytotoxic activity at concentrations of <10 μM. Polyphemusin III caused fast permeabilization of the cytoplasmic membrane of human leukemia cells HL-60, which was measured with trypan blue exclusion assay and lactate dehydrogenase-release assay. Flow cytometry experiments for annexin V-FITC/ propidium iodide double staining revealed that the caspase inhibitor, Z-VAD-FMK, did not abrogate disruption of the plasma membrane by polyphemusin III. Our data suggest that polyphemusin III disrupts the plasma membrane integrity and induces cell death that is apparently not related to apoptosis. In comparison to known polyphemusins and tachyplesins, polyphemusin III demonstrates a similar or lower antimicrobial effect, but significantly higher cytotoxicity against human cancer and transformed cells in vitro.

[Beyond antibiotic therapy - Future antiinfective strategies - Update 2017]

BACKGROUND

The key elements in the therapy of surgical site infections (SSI) are surgical debridement and local and systemic antibiotic therapy; however, due to increasing antibiotic resistance, the development of additional therapeutic measures is of great interest for future trauma and orthopedic surgery.

METHOD

Against the background of our own experimental and clinical experiences and on the basis of the current literature, possible future anti-infective strategies were elaborated.

RESULTS/CONCLUSIONS

Bacteriophages were discovered and clinically implemented approximately one century ago and have been used in Western Europe for about one decade. They are currently used mainly in patients with burn injuries. It is likely that bacteriophages will become of great importance in view of the increasing antibiotic multi-drug resistance; however, they will probably not entirely replace antibiotic drugs. A combined use of bacteriophages and antibiotics is likely to be a more reasonable efficient therapy. In addition, the clinical importance of antimicrobial peptides (AMP) also increases. Up to now the possible use of AMPs is still experimental; however, individual AMPs are already established in the routine therapy (e. g. colistin). Further diagnostic and therapeutic measures may include photodynamic therapy, ultraviolet (UV) light application and differentiated genome analysis as well as the individual metabolism situation (metabolomics) of the pathogen cell and the patient tissue.

New Innovations in the Treatment of PJI and Biofilms-Clinical and Preclinical Topics

PURPOSE OF REVIEW

Periprosthetic joint infection (PJI) is a devastating complication after total joint replacement. A main source for antibiotic tolerance and treatment failure is bacterial production of biofilm-a resilient barrier against antibiotics, immune system, and mechanical debridement. The purpose of this review is to explore some novel approaches to treat PJI and biofilm-related infections.

RECENT FINDINGS

Innovative treatment strategies of bacterial and biofilm infections revolve around (a) augmenting current therapies, such as improving the delivery and efficiency of conventional antibiotics and enhancing the efficacy of antiseptics and (b) administrating completely new therapeutic modalities, such as using immunotherapy, nanoparticles, lytic bacteriophages, photodynamic therapy, novel antibiotics, and antimicrobial peptides. Several promising treatment strategies for PJI are available to be tested further. The next requirement for most of the novel treatments is reproducing their effects in clinically representative animal models of PJI against clinical isolates of relevant bacteria.

New Perspectives in Biofilm Eradication

Microbial biofilms, which are elaborate and highly resistant microbial aggregates formed on surfaces or medical devices, cause two-thirds of infections and constitute a serious threat to public health. Immunocompromised patients, individuals who require implanted devices, artificial limbs, organ transplants, or external life support and those with major injuries or burns, are particularly prone to become infected. Antibiotics, the mainstay treatments of bacterial infections, have often proven ineffective in the fight against microbes when growing as biofilms, and to date, no antibiotic has been developed for use against biofilm infections. Antibiotic resistance is rising, but biofilm-mediated multidrug resistance transcends this in being adaptive and broad spectrum and dependent on the biofilm growth state of organisms. Therefore, the treatment of biofilms requires drug developers to start thinking outside the constricted "antibiotics" box and to find alternative ways to target biofilm infections. Here, we highlight recent approaches for combating biofilms focusing on the eradication of preformed biofilms, including electrochemical methods, promising antibiofilm compounds and the recent progress in drug delivery strategies to enhance the bioavailability and potency of antibiofilm agents.