Multiple roles of ribosomal antimicrobial peptides in tackling global antimicrobial resistance

Dual Antimicrobial and Anticancer Activity of Membrane-Active Peptide BP52

The linear undecapeptide BP52 was previously reported to have antibacterial activity against phytopathogenic bacteria species. Due to the structural similarities to naturally occurring cationic helical antimicrobial peptides, it was speculated that this peptide could potentially target microbial pathogens and cancer cells found in mammals. Consequently, this study aims to further investigate the structural and biological properties of this peptide. Our findings indicate that BP52 exhibits strong antimicrobial and anticancer activity while displaying relatively low levels of hemolytic activity. Hence, this study suggests that BP52 could be a potential lead compound for drug discovery against infectious diseases and cancer. Besides, new insights into the relationships between the structure and the multifunctional properties of antimicrobial peptides were also explored.

Impact of lipidation site on the activity of α-helical antimicrobial peptides

Antimicrobial peptides (AMPs) display advantages over traditional antibiotics due to their broad spectrum of activity against various pathogens, and may even overcome bacterial drug resistance. However, despite their potential therapeutic benefits, widespread application of AMPs is limited by their instability, sensitivity to high salt concentrations, toxicity, and immunogenicity. Lipidation is a promising strategy in overcoming these drawbacks and potential problems for drug candidates. While N-terminal lipidation is a well-studied form of acylation of biologically active peptides, fatty acylation of the lysine side chain has still been poorly explored. In this study, we examined systematic introduction of octanoic (C8) or decanoic (C10) acid into the sequences of three antimicrobial α-helical peptides, namely LL-I, LK6, and ATRA-1, by acylation of subsequent lysine residues, resulting in 17 lipopeptides. Fatty acid lengths optimal for antimicrobial activity were selected based on a previous study on the N-terminal lipidated counterparts of these peptides. Shuffling the position of the fatty acid tails in the sequences of the peptides preserved high activity against Gram-positive bacteria, increased activity against Gram-negative strains and reduced cytotoxicity, compared to the N-terminal acylated counterparts. In the case of the LL-I and LK6 conjugates, the interactions with artificial negatively charged membranes induced formation of an α-helical structure but without a direct correlation between helicity and amphipathicity. Unexpectedly, the ATRA-1 derivatives showed only a small tendency, if any, to adopt a helical structure upon binding to POPG vesicles, which may indicate a non-helical active conformation. A more detailed study of the selected analogues, namely LL-I-4C8, LK6-7C8, and ATRA-1-11C10, provided evidence of a tendency to self-assemble into clumped and/or isolated fibrils, micelles or clusters of micelles, and proved that the lipid bilayer is the main target of action of the tested lipopeptides. In summary, the results of the present study highlight that alternative conjugation sites for lipid modification of AMPs, rather than the commonly applied N-terminal conjugation site, may improve the selectivity of action and be feasible in testing for the development of new lipid-peptide conjugates.

Current treatment strategies for targeting virulence factors and biofilm formation in Acinetobacter baumannii

A higher prevalence of Acinetobacter baumannii infections and mortality rate has been reported recently in hospital-acquired infections (HAI). The biofilm-forming capability of A. baumannii makes it an extremely dangerous pathogen, especially in device-associated hospital-acquired infections (DA-HAI), thereby it resists the penetration of antibiotics. Further, the transmission of the SARS-CoV-2 virus was exacerbated in DA-HAI during the epidemic. This review specifically examines the complex interconnections between several components and genes that play a role in the biofilm formation and the development of infections. The current review provides insights into innovative treatments and therapeutic approaches to combat A. baumannii biofilm-related infections, thereby ultimately improving patient outcomes and reducing the burden of HAI.

Navigating Antibacterial Frontiers: A Panoramic Exploration of Antibacterial Landscapes, Resistance Mechanisms, and Emerging Therapeutic Strategies

The development of effective antibacterial solutions has become paramount in maintaining global health in this era of increasing bacterial threats and rampant antibiotic resistance. Traditional antibiotics have played a significant role in combating bacterial infections throughout history. However, the emergence of novel resistant strains necessitates constant innovation in antibacterial research. We have analyzed the data on antibacterials from the CAS Content Collection, the largest human-curated collection of published scientific knowledge, which has proven valuable for quantitative analysis of global scientific knowledge. Our analysis focuses on mining the CAS Content Collection data for recent publications (since 2012). This article aims to explore the intricate landscape of antibacterial research while reviewing the advancement from traditional antibiotics to novel and emerging antibacterial strategies. By delving into the resistance mechanisms, this paper highlights the need to find alternate strategies to address the growing concern.

The amphipathic design in helical antimicrobial peptides

Amphipathicity is a critical characteristic of helical antimicrobial peptides (AMPs). The hydrophilic region, primarily composed of cationic residues, plays a pivotal role in the initial binding to negatively charged components on bacterial membranes through electrostatic interactions. Subsequently, the hydrophobic region interacts with hydrophobic components, inducing membrane perturbation, ultimately leading to cell death, or inhibiting intracellular function. Due to the extensive diversity of natural and synthetic AMPs with regard to the design of amphipathicity, it is complicated to study the structure-activity relationships. Therefore, this work aims to categorize the common amphipathic design and investigate their impact on the biological properties of AMPs. Besides, the connection between current structural modification approaches and amphipathic styles was also discussed.

A hope for ineffective antibiotics to return to treatment: investigating the anti-biofilm potential of melittin alone and in combination with penicillin and oxacillin against multidrug resistant-MRSA and -VRSA

Background

The emergence and rapid spread of multi-drug resistant (MDR) bacterial strains, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant S. aureus (VRSA), have posed a significant challenge to the medical community due to their ability to form biofilm and develop resistance to common antibiotics. Traditional antibiotics that were once effective in treating bacterial infections are now becoming increasingly ineffective, leading to severe consequences for patient outcomes. This concerning situation has called for urgent research to explore alternative treatment strategies. Recent studies have shown that antimicrobial peptides (AMPs) hold promise as effective agents against biofilm-associated drug-resistant infections as well as to enhance the efficacy of conventional antibiotics. Accordingly, we aimed to investigate the antimicrobial and antibiofilm effects of melittin AMP, both alone and in combination with penicillin and oxacillin, against biofilm-forming MDR-MRSA and -VRSA.

Methods

In this study, we investigated the kinetics of biofilm formation and assessed various parameters related to the antimicrobial and antibiofilm efficacy of melittin and antibiotics, both alone and in combination, against MDR-MRSA and -VRSA. The antimicrobial parameters included the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC), Fractional Inhibitory Concentration Index (FICi), Fractional Bactericidal Concentration Index (FBCi), and the antibiofilm activity of melittin and antibiotics indicated by the Minimum Biofilm Inhibitory Concentration (MBIC), Minimal Biofilm Eradication Concentration (MBEC), Fractional Biofilm Inhibitory Concentration Index (FBICi), and Fractional Biofilm Eradication Concentration Index (FBECi).

Results

The MIC results showed that all S. aureus isolates were resistant to penicillin (≥0.25 μg/mL), and 66% of isolates were resistant to oxacillin. The geometric means of the MIC values for penicillin, oxacillin, and melittin were 19.02, 16, and 1.62 μg/ml, respectively, and the geometric means of the MBC values for penicillin, oxacillin, and melittin were 107.63, 49.35, and 5.45 μg/ml, respectively. The study revealed that the combination indexes of melittin-penicillin and melittin-oxacillin, as determined by FIC values against all isolates, were 0.37 and 0.03, respectively. Additionally, melittin-penicillin and melittin-oxacillin exhibited combination indexes based on FBC values against all isolates at 1.145 and 0.711, respectively. Besides, melittin inhibited the biofilm formation of all S. aureus isolates, with MBIC values ranging from 10 to 1.25 μg/mL, and MBEC values ranging from 40 to 10 μg/mL. Generally, the combination indexes of melittin-penicillin and melittin-oxacillin, determined using FBIC values against all isolates, were 0.23 and 0.177, respectively. Moreover, melittin-penicillin and melittin-oxacillin typically had combination indexes based on FBEC values against all isolates at 5 and 2.97, respectively.

Conclusion

In conclusion, our study provides evidence that melittin is effective against both planktonik and biofilm forms of MRSA and VRSA and exhibits significant synergistic effects when combined with antibiotics. These results suggest that melittin and antibiotics could be a potential candidate for further investigation for in vivo infections caused by MDR S. aureus. Furthermore, melittin has the potential to restore the efficacy of penicillin and oxacillin antibiotics in the treatment of MDR infections. Applying AMPs, like melittin, to revive beta-lactam antibiotics against MRSA and VRSA is an innovative approach against antibiotic-resistant bacteria. Further research is needed to optimize dosage and understand melittin mechanism and interactions with beta-lactam antibiotics for successful clinical applications.

Impact of chemical modifications on the antimicrobial and hemolytic activity of helical amphipathic peptide Lasioglossin LL-III

Insect venom is abundant in potential antimicrobial peptides (AMPs), which can serve as novel alternatives to conventional antibiotics. Among them, Lasioglossin III LL-III) is a promising candidate with a broad spectrum against many fungi strains and both types of bacteria, whereas almost non-toxic to red blood cells. Many chemical approaches have been recently applied to improve its pharmacological properties and provide useful information regarding structure-activity relationships. Hence, this review focused on highlighting the lesson learned from each modification and supporting the future design of potent, selective, and metabolically stable AMPs.

In-depth biological characterization of two black soldier fly anti-Pseudomonas peptides reveals LPS-binding and immunomodulating effects

As effector molecules of the innate immune system, antimicrobial peptides (AMPs) have gathered substantial interest as a potential future generation of antibiotics. Here, we demonstrate the anti-Pseudomonas activity and lipopolysaccharide (LPS)-binding ability of HC1 and HC10, two cecropin peptides from the black soldier fly (Hermetia Illucens). Both peptides are active against a wide range of Pseudomonas aeruginosa strains, including drug-resistant clinical isolates. Moreover, HC1 and HC10 can bind to lipid A, the toxic center of LPS and reduce the LPS-induced nitric oxide and cytokine production in murine macrophage cells. This suggests that the peptide-LPS binding can also lower the strong inflammatory response associated with P. aeruginosa infections. As the activity of AMPs is often influenced by the presence of salts, we studied the LPS-binding activity of HC1 and HC10 in physiological salt concentrations, revealing a strong decrease in activity. Our research confirmed the early potential of HC1 and HC10 as starting points for anti-Pseudomonas drugs, as well as the need for structural or formulation optimization before further preclinical development can be considered. IMPORTANCE The high mortality and morbidity associated with Pseudomonas aeruginosa infections remain an ongoing challenge in clinical practice that requires urgent action. P. aeruginosa mostly infects immunocompromised individuals, and its prevalence is especially high in urgent care hospital settings. Lipopolysaccharides (LPSs) are outer membrane structures that are responsible for inducing the innate immune cascade upon infection. P. aeruginosa LPS can cause local excessive inflammation, or spread systemically throughout the body, leading to multi-organ failure and septic shock. As antimicrobial resistance rates in P. aeruginosa infections are rising, the research and development of new antimicrobial agents remain indispensable. Especially, antimicrobials that can both kill the bacteria themselves and neutralize their toxins are of great interest in P. aeruginosa research to develop as the next generation of drugs.

Novel Genetically Engineered Probiotics for Targeted Elimination of Pseudomonas aeruginosa in Intestinal Colonization

The intestinal carriage rates of Pseudomonas aeruginosa are notably elevated in immunosuppressed individuals and hospitalized patients, increasing the risk of infection and antibiotic-associated diarrhea. A potential solution to this issue lies in autonomous antibacterial therapy, remaining inactive until a pathogen is detected, and releasing antibacterial compounds on demand to eliminate the pathogen. This study focuses on the development of genetically engineered probiotics capable of detecting and eradicating P. aeruginosa by producing and secreting PA2-GNU7, a P. aeruginosa-selective antimicrobial peptide (AMP), triggered by the presence of P. aeruginosa quorum-sensing molecule N-(3-oxododecanoyl)-L-homoserine lactone (3OC12HSL). To achieve this goal, plasmid-based systems were constructed to produce AMPs in response to 3OC12HSL and secrete them into the extracellular medium using either the microcin V secretion system or YebF as a carrier protein. Following the transfer of these plasmid-based systems to Escherichia coli Nissle 1917 (EcN), we successfully demonstrated the ability of the engineered EcN to express and secrete PA2-GNU7, leading to the inhibition of P. aeruginosa growth in vitro. In addition, in a mouse model of intestinal P. aeruginosa colonization, the administration of engineered EcN resulted in reduced levels of P. aeruginosa in both the feces and the colon. These findings suggest that engineered EcN holds promise as a potential option for combating intestinal P. aeruginosa colonization, thus mitigating the risk of future endogenous infections in vulnerable patients.

Effect of substituting glutamine with lysine on structural and biological properties of antimicrobial peptide Polybia-MP1

The natural antimicrobial peptide Polybia-MP1 is a promising candidate for developing new treatment therapy for infection and cancer. It showed broad-spectrum antimicrobial and anticancer activity with high safety on healthy cells. However, previous sequence modification usually resulted in at least one of two consequences: a notable increase in hemolytic activity or a considerable decrease in activity against Gram-negative bacteria and cancer cells. Herein, a new approach was applied by replacing the amino acid Glutamine at position 12 with Lysine and generating the MP1-Q12K analog. Our preliminary data suggested an enhancement in antibacterial and antifungal activity, whereas the anticancer and hemolytic activity of the two peptides were comparable. Moreover, MP1-Q12K was found to be less self-assembly than Polybia-MP1, which further supports the enhancement of antimicrobial properties. Hence, this study provides new information regarding the structure-activity relationships of Polybia-MP1 and support for the development of potent, selective antimicrobial peptides.

R R, L. F L, M.C.G DR, N.B C, S.C D, O. L F. Advances and perspectives for antimicrobial peptide and combinatory therapies

Antimicrobial peptides (AMPs) have shown cell membrane-directed mechanisms of action. This specificity can be effective against infectious agents that have acquired resistance to conventional drugs. The AMPs' membrane-specificity and their great potential to combat resistant microbes has brought hope to the medical/therapeutic scene. The high death rate worldwide due to antimicrobial resistance (AMR) has pushed forward the search for new molecules and product developments, mainly antibiotics. In the current scenario, other strategies including the association of two or more drugs have contributed to the treatment of difficult-to-treat infectious diseases, above all, those caused by bacteria. In this context, the synergistic action of AMPs associated with current antibiotic therapy can bring important results for the production of new and effective drugs to overcome AMR. This review presents the advances obtained in the last 5 years in medical/antibiotic therapy, with the use of products based on AMPs, as well as perspectives on the potentialized effects of current drugs combined with AMPs for the treatment of bacterial infectious diseases.