Next-Generation Antibiotics, Bacteriophage Endolysins, and Nanomaterials for Combating Pathogens

Antimicrobial peptide A20L: in vitro and in vivo antibacterial and antibiofilm activity against carbapenem-resistant Klebsiella pneumoniae

Antimicrobial resistance has become a growing public health threat in recent years. Klebsiella pneumoniae is one of the priority pathogens listed by the World Health Organization. Antimicrobial peptides are considered promising alternatives to antibiotics due to their broad-spectrum antibacterial activity and low resistance. In this study, we investigated the antibacterial activity of antimicrobial peptide A20L against K. pneumoniae. In vitro antibacterial activity of A20L against K. pneumoniae was demonstrated by broth microdilution method. We confirmed the in vivo efficacy of A20L by Galleria mellonella infection model. In addition, we found that A20L also had certain antibiofilm activity by crystal violet staining. We also evaluated the safety and stability of A20L, and the results revealed that at a concentration of ≤128 µg/mL, A20L exhibited negligible toxicity to RAW264.7 cells and no substantial toxicity to G. mellonella. A20L was stable at different temperatures and with low concentration of serum [5% fetal bovine serum (FBS)]; however, Ca2+, Mg2+, and high serum concentrations reduced the antibacterial activity of A20L. Scanning electron microscope (SEM) and membrane permeability tests revealed that A20L may exhibit antibacterial action by damaging bacterial cell membranes and increasing the permeability of outer membrane. Taken together, our results suggest that A20L has significant development potential as a therapeutic antibiotic alternative, which provides ideas for the treatment of K. pneumoniae infection.

IMPORTANCE

A20L showed antibacterial and anti-infective efficacy in vitro and in vivo against Klebsiella pneumoniae. It can have an antibacterial effect by disrupting the integrity of cell membranes. A20L displayed anti-biofilm and anti-inflammatory activity against carbapenem-resistant K. pneumoniae and certain application potential in vivo, which provides a new idea for the clinical treatment of biofilm-associated infections.

Is It Possible to Create Antimicrobial Peptides Based on the Amyloidogenic Sequence of Ribosomal S1 Protein of P. aeruginosa?

The development and testing of new antimicrobial peptides (AMPs) represent an important milestone toward the development of new antimicrobial drugs that can inhibit the growth of pathogens and multidrug-resistant microorganisms such as Pseudomonas aeruginosa, Gram-negative bacteria. Most AMPs achieve these goals through mechanisms that disrupt the normal permeability of the cell membrane, which ultimately leads to the death of the pathogenic cell. Here, we developed a unique combination of a membrane penetrating peptide and peptides prone to amyloidogenesis to create hybrid peptide: "cell penetrating peptide + linker + amyloidogenic peptide". We evaluated the antimicrobial effects of two peptides that were developed from sequences with different propensities for amyloid formation. Among the two hybrid peptides, one was found with antibacterial activity comparable to antibiotic gentamicin sulfate. Our peptides showed no toxicity to eukaryotic cells. In addition, we evaluated the effect on the antimicrobial properties of amino acid substitutions in the non-amyloidogenic region of peptides. We compared the results with data on the predicted secondary structure, hydrophobicity, and antimicrobial properties of the original and modified peptides. In conclusion, our study demonstrates the promise of hybrid peptides based on amyloidogenic regions of the ribosomal S1 protein for the development of new antimicrobial drugs against P. aeruginosa.

Use of Recombinant Endolysin to Improve Accuracy of Group B Streptococcus Tests

Group B Streptococcus (GBS) causes serious neonatal infection via vertical transmission. The prenatal GBS screening test is performed at the late stage of pregnancy to avoid risks of infection. In this test, enrichment culture is performed, followed by GBS identification. Selective medium is used for the enrichment; however, Enterococcus faecalis, which is a potential contaminant in swab samples, can interfere with the growth of GBS. Such bacterial contamination can lead to false-negative results. Endolysin, a bacteriophage-derived enzyme, degrades peptidoglycan in the bacterial cell wall; it is a promising antimicrobial agent for selectively eliminating specific bacterial genera/species. In this study, we used the recombinant endolysin EG-LYS, which is specific to E. faecalis; the endolysin potentially enriched GBS in the selective culture. First, in the false-negative model (coculture of GBS and E. faecalis, which disabled GBS detection in the subsequent GBS identification test), EG-LYS treatment at 0.1 mg/ml improved GBS detection. Next, we used 548 vaginal swabs to test the efficacy of EG-LYS treatment in improving GBS detection. EG-LYS treatment (0.1 mg/ml) increased the GBS-positive ratio to 17.9%, compared to 15.7% in the control (phosphate-buffered saline [PBS] treatment). In addition, there were an increased number of GBS colonies under EG-LYS treatment in some samples. The results were supported by the microbiota analysis of the enriched cultures. In conclusion, EG-LYS treatment of the enrichment culture potentially improves the accuracy of the prenatal GBS screening test. IMPORTANCE Endolysin is a bacteriophage-derived enzyme that degrades the peptidoglycan in the cell wall of host bacteria; it could be used as an antimicrobial agent for selectively eliminating specific bacterial genera/species. Group B Streptococcus (GBS) causes neonatal infection via vertical transmission; prenatal GBS screening test, in which enrichment culture is followed by bacterial identification, is used to detect the presence of GBS in pregnant women. However, the presence of commensal bacteria such as Enterococcus faecalis in clinical specimens can inhibit GBS growth in the selective enrichment culture, resulting in false-negative result. Here, we demonstrated that the application of originally isolated endolysin in the enrichment culture improved the test accuracy by inhibiting unwanted E. faecalis growth and therefore avoiding false-negative results, not only in experimental settings, but also in tests using vaginal swabs.

Overcoming Antibiotic Resistance in Microorganisms: Molecular Mechanisms

This issue of the Biochemistry (Moscow) journal presents reviews and experimental articles on the new strategies for solving the problem of antibiotic resistance and on the search for novel antimicrobial preparations using the methods of molecular biology, genetics, and nanotechnology. A wide variety of scientific approaches and successful (as a rule) research results give hope for overcoming microbial antibiotic resistance in the fight against infectious diseases.