Antimicrobial Random Peptide Mixtures Eradicate Acinetobacter baumannii Biofilms and Inhibit Mouse Models of Infection

Targeting the phosphatidylglycerol lipid: An amphiphilic dendrimer as a promising antibacterial candidate

The rapid emergence and spread of multidrug-resistant bacterial pathogens require the development of antibacterial agents that are robustly effective while inducing no toxicity or resistance development. In this context, we designed and synthesized amphiphilic dendrimers as antibacterial candidates. We report the promising potent antibacterial activity shown by the amphiphilic dendrimer AD1b, composed of a long hydrophobic alkyl chain and a tertiary amine-terminated poly(amidoamine) dendron, against a panel of Gram-negative bacteria, including multidrug-resistant Escherichia coli and Acinetobacter baumannii. AD1b exhibited effective activity against drug-resistant bacterial infections in vivo. Mechanistic studies revealed that AD1b targeted the membrane phospholipids phosphatidylglycerol (PG) and cardiolipin (CL), leading to the disruption of the bacterial membrane and proton motive force, metabolic disturbance, leakage of cellular components, and, ultimately, cell death. Together, AD1b that specifically interacts with PG/CL in bacterial membranes supports the use of small amphiphilic dendrimers as a promising strategy to target drug-resistant bacterial pathogens and addresses the global antibiotic crisis.

Photodynamic black phosphorus nanosheets functionalized with polymyxin B for targeted ablation of drug-resistant mixed-species biofilms

Biofilms, particularly those formed by multiple bacterial species, pose significant economic and environmental challenges, especially in the context of medical implants. Addressing the urgent need for effective treatment strategies that do not exacerbate drug resistance, we developed a novel nanoformulation, Ce6&PMb@BPN, based on black phosphorus nanosheets (BPN) for targeted treatment of mixed-species biofilms formed by Acinetobacter baumannii (A. baumannii) and methicillin-resistant Staphylococcus aureus (MRSA).The formulation leverages polymyxin B (PMb) for bacterial targeting and chlorin e6 (Ce6) for photodynamic action. Upon near-infrared (NIR) irradiation, Ce6&PMb@BPN efficiently eliminates biofilms by combining chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT), reducing biofilm biomass significantly within 30 min. In vivo studies on mice infected with mixed-species biofilm-coated catheters demonstrated the formulation's potent antibacterial and biofilm ablation effects. Moreover, comprehensive biosafety evaluations confirmed the excellent biocompatibility of Ce6&PMb@BPN. Taken together, this intelligently designed nanoformulation holds potential for effectively treating biofilm-associated infections, addressing the urgent need for strategies to combat antibiotic-resistant biofilms, particularly mixed-species biofilm, in medical settings.

Synergistic action of antimicrobial peptides and antibiotics: current understanding and future directions

Antibiotic resistance is a growing global problem that requires innovative therapeutic approaches and strategies for administering antibiotics. One promising approach is combination therapy, in which two or more drugs are combined to combat an infection. Along this line, the combination of antimicrobial peptides (AMPs) with conventional antibiotics has gained attention mainly due to the complementary mechanisms of action of AMPs and conventional antibiotics. In this article, we review both in vitro and in vivo studies that explore the synergy between AMPs and antibiotics. We highlight several mechanisms through which synergy is observed in in vitro experiments, including increasing membrane permeability, disrupting biofilms, directly potentiating antibiotic efficacy, and inhibiting resistance development. Moreover, in vivo studies reveal additional mechanisms such as enhanced/modulated immune responses, reduced inflammation, and improved tissue regeneration. Together, the current literature demonstrates that AMP-antibiotic combinations can substantially enhance efficacy of antibiotic therapies, including therapies against resistant bacteria, which represents a valuable enhancement to current antimicrobial strategies.

Amphiphilic Dendrimer as Potent Antibacterial against Drug-Resistant Bacteria in Mouse Models of Human Infectious Diseases

Modern medicine continues to struggle against antibiotic-resistant bacterial pathogens. Among the pathogens of critical concerns are the multidrug-resistant (MDR) Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. These pathogens are major causes of nosocomial infections among immunocompromised individuals, involving major organs such as lung, skin, spleen, kidney, liver, and bloodstream. Therefore, novel approaches are direly needed. Recently, we developed an amphiphilic dendrimer DDC18-8A exhibiting high antibacterial and antibiofilm efficacy in vitro. DDC18-8A is composed of a long hydrophobic alkyl chain and a small hydrophilic poly(amidoamine) dendron bearing amine terminals, exerting its antibacterial activity by attaching and inserting itself into bacterial membranes to trigger cell lysis. Here, we examined the pharmacokinetics and in vivo toxicity as well as the antibacterial efficacy of DDC18-8A in mouse models of human infectious diseases. Remarkably, DDC18-8A significantly reduced the bacterial burden in mouse models of acute pneumonia and bacteremia by P. aeruginosa, methicillin-resistant S. aureus (MRSA), and carbapenem-resistant K. pneumoniae and neutropenic soft tissue infection by P. aeruginosa and MRSA. Most importantly, DDC18-8A outperformed pathogen-specific antibiotics against all three pathogens by achieving a similar bacterial clearance at 10-fold lower therapeutic concentrations. In addition, it showed superior stability and biodistribution in vivo, with excellent safety profiles yet without any observable abnormalities in histopathological analysis of major organs, blood serum biochemistry, and hematology. Collectively, we provide strong evidence that DDC18-8A is a promising alternative to the currently prescribed antibiotics in addressing challenges associated with nosocomial infections by MDR pathogens.

Antibacterial efficacy of an ultra-short palmitoylated random peptide mixture in mouse models of infection by carbapenem-resistant Klebsiella pneumoniae

Indiscriminate use of antibiotics has imposed a selective pressure for the rapid rise in bacterial resistance, creating an urgent need for novel therapeutics for managing bacterial infectious diseases while counteracting bacterial resistance. Carbapenem-resistant Klebsiella pneumoniae strains have become a major challenge in modern medicine due to their ability to cause an array of severe infections. Recently, we have shown that the 20-mer random peptide mixtures are effective therapeutics against three ESKAPEE pathogens. Here, we evaluated the toxicity, biodistribution, bioavailability, and efficacy of the ultra-short palmitoylated 5-mer phenylalanine:lysine (FK5P) random peptide mixtures against multiple clinical isolates of carbapenem-resistant K. pneumoniae and K. oxytoca. We demonstrate the FK5P rapidly and effectively killed various strains of K. pneumoniae, inhibited the formation of biofilms, and disrupted mature biofilms. FK5P displayed strong toxicity profiles both in vitro and in mice, with prolonged favorable biodistribution and a long half-life. Significantly, FK5P reduced the bacterial burden in mouse models of acute pneumonia and bacteremia and increased the survival rate in a mouse model of bacteremia. Our results demonstrate that FK5P is a safe and promising therapy against Klebsiella species as well as other ESKAPEE pathogens.

Pyrogallol downregulates the expression of virulence-associated proteins in Acinetobacter baumannii and showing anti-infection activity by improving non-specific immune response in zebrafish model

Acinetobacter baumannii, a virulent uropathogen with widespread antibiotic resistance, has arisen as a critical scientific challenge, necessitating the development of innovative therapeutic agents. This is the first study reveal the proteomic changes in A. baumannii upon pyrogallol treatment for understanding the mechanisms using nano-LC-MS/MS-based quantitative proteomics and qPCR analysis. The obtained results found that pyrogallol treatment dramatically downregulated the expression level of several key proteins such as GroEL, DnaK, ClpB, SodB, KatE, Bap, CsuA/B, PgaA, PgaC, BfmR, OmpA, and SecA in A. baumannii, which are involved in chaperone-mediated oxidative stress responses, antioxidant defence system, biofilm formation, virulence enzyme production, bacterial adhesion, capsule formation, and antibiotic resistance. Accordingly, the pyrogallol dramatically enhanced the lifespan of A. baumannii-infected zebrafish by inhibiting bacterial colonization, demonstrating the anti-infective potential of pyrogallol against A. baumannii. Further, the histopathological results also demonstrated the disease protection efficacy of pyrogallol against the pathognomonic sign of A. baumannii infection. In addition, the pyrogallol treatment effectively improved the immune parameters such as serum myeloperoxidase activity, leukocyte respiratory burst activity, and serum lysozyme activity in zebrafish against A. baumannii infection. Based on the results, the present study strongly proposes pyrogallol as a promising therapeutic agent for treating A. baumannii infection.

Impedimetric Bacterial Detection Using Random Antimicrobial Peptide Mixtures

The biosensing of bacterial pathogens is of a high priority. Electrochemical biosensors are an important future tool for rapid bacteria detection. A monolayer of bacterial-binding peptides can serve as a recognition layer in such detection devices. Here, we explore the potential of random peptide mixtures (RPMs) composed of phenylalanine and lysine in random sequences and of controlled length, to form a monolayer that can be utilized for sensing. RPMs were found to assemble in a thin and diluted layer that attracts various bacteria. Faradaic electrochemical impedance spectroscopy was used with modified gold electrodes to measure the charge-transfer resistance (RCT) caused due to the binding of bacteria to RPMs. Pseudomonas aeruginosa was found to cause the most prominent increase in RCT compared to other model bacteria. We show that the combination of highly accessible antimicrobial RPMs and electrochemical analysis can be used to generate a new promising line of bacterial biosensors.

Antimicrobial Peptide Cec4 Eradicates Multidrug-Resistant Acinetobacter baumannii in vitro and in vivo

Introduction

Acinetobacter baumannii has become a major difficulty in the treatment of bacteria-associated infection. The previously reported antimicrobial peptide Cec4 exhibited good and stable activity against A. baumannii in vitro, but the mechanisms and effects in vivo are elusive.

Methods

The effects of Cec4 on bacterial membrane permeability, membrane potential and bacterial reactive oxygen species were measured. The cell membrane localization of antimicrobial peptides was studied by fluorescence labelling. The ability of bacteria to develop resistance to antimicrobial peptides was studied by continuous induction, and transcriptome difference was analysed. The in vivo toxicity of Cec4 against nematodes and mice was studied, and the in vivo therapeutic potential of Cec4 against A. baumannii was assessed.

Results

Cec4 effectively cleared multidrug-resistant A. baumannii by altering bacterial cell membrane permeability, changing bacterial cell membrane polarity, and increasing bacterial intracellular reactive oxygen species. Cec4 affected the expression of the secretion system, outer membrane, and efflux pump genes of A. baumannii. In addition, the bacteria did not acquire stable drug-resistant ability. Cec4 at 1.024 mg/mL did not affect the proliferation of HeLa and HepG2 cells, and Cec4 at 45 mg/kg had little effect on the mortality of Caenorhabditis elegans, even the liver and kidney tissues of mouse. Most importantly, Cec4 could effectively improve the survival rates and reduce the bacterial load of various tissues in the mouse model of infection.

Conclusion

In conclusion, Cec4 can damage the cell membrane of bacteria, and the bacteria is not easy to produce resistance to Cec4. Besides, Cec4 has good potential for the treatment of multidrug-resistant A. baumannii infections.

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.

Synthesis and Characterization of Preacinetobactin and 5-Phenyl Preacinetobactin

We report the first total synthesis of 5-phenyl preacinetobactin and its characterization. The route was developed for the synthesis of preacinetobactin, the siderophore critical to the Gram-negative pathogen A. baumannii. It leverages a C5-substituted benzaldehyde as a key starting material and should enable the synthesis of similar analogs. 5-Phenyl preacinetobactin binds iron in a manner analogous to the natural siderophore, but it did not rescue growth in a strain of A. baumannii unable to produce preacinetobactin.