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

Random antimicrobial peptide mixtures as non-antibiotic antimicrobial agents for cultured meat industry

Antibiotics, commonly used in cell culture studies to prevent microbial contamination, cannot be employed in Cultured meat (CM) due to potential residues in the final food products. Hence, there is an urgent need to develop novel and safe non-antibiotic antimicrobial agents. Here, we investigated the potential of random antimicrobial peptide mixtures (RPMs) as non-antibiotic antimicrobial agents. RPMs are synthetic peptide cocktails that have previously shown strong and broad antimicrobial activity; however, their use in cell culture media and their effect on mammalian cells have not yet been explored. Here we show that RPMs had no significant impact on mesenchymal stem cells (MSCs) at concentrations that effectively inhibit bacterial growth. RPMs displayed strong bactericidal activity against Gram-positive bacteria, achieving a 6-log reduction of L. monocytogenes in cell culture medium without any cytotoxicity. Additionally, RPMs showed a low occurrence of resistance development with no significant resistance developed in compared with a combination of penicillin and streptomycin. Moreover, LK20 mixture was rapidly digested and a rapid digestion in a simulated digestion model. Our results indicate that RPMs have great potential to serve as safe and effective non antibiotic antimicrobial agents in cultured meat industry.

Cell-autonomous innate immunity by proteasome-derived defence peptides

For decades, antigen presentation on major histocompatibility complex class I for T cell-mediated immunity has been considered the primary function of proteasome-derived peptides1,2. However, whether the products of proteasomal degradation play additional parts in mounting immune responses remains unknown. Antimicrobial peptides serve as a first line of defence against invading pathogens before the adaptive immune system responds. Although the protective function of antimicrobial peptides across numerous tissues is well established, the cellular mechanisms underlying their generation are not fully understood. Here we uncover a role for proteasomes in the constitutive and bacterial-induced generation of defence peptides that impede bacterial growth both in vitro and in vivo by disrupting bacterial membranes. In silico prediction of proteome-wide proteasomal cleavage identified hundreds of thousands of potential proteasome-derived defence peptides with cationic properties that may be generated en route to degradation to act as a first line of defence. Furthermore, bacterial infection induces changes in proteasome composition and function, including PSME3 recruitment and increased tryptic-like cleavage, enhancing antimicrobial activity. Beyond providing mechanistic insights into the role of proteasomes in cell-autonomous innate immunity, our study suggests that proteasome-cleaved peptides may have previously overlooked functions downstream of degradation. From a translational standpoint, identifying proteasome-derived defence peptides could provide an untapped source of natural antibiotics for biotechnological applications and therapeutic interventions in infectious diseases and immunocompromised conditions.

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.