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- Musa, Amani, 1983-
(author)
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Plantaricins as a novel group of antibacterial compounds and enhancers of antibiotics
- 2022
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Doctoral thesis (other academic/artistic)abstract
- Antibiotics have revolutionized medicine, however, the rapid development of an-tibiotic resistance among bacteria is diminishing their efficacy. Antimicrobial pep-tides produced by Lactobacillus plantarum, i.e., plantaricins, are considered prom-ising alternatives to antibiotics against infections. In this thesis, the antimicrobial activities of different plantaricins (Pln A, Pln EF, Pln JK, and PLNC8 αβ) were investigated against antibiotic-resistant and susceptible strains of Staphylococcus spp, biofilm-forming strains, as well as clinical isolates of ESKAPE pathogens, and Escherichia coli. Moreover, the stability, cytotoxicity, and immunomodulatory effects of PLNC8 αβ were characterized. The results show that Pln EF and Pln JK have potent antimicrobial activity against Staphylococcus epidermidis and effectively enhance the effects of various antibiotics. Furthermore, PLNC8 αβ shows potent antibacterial effects against different Gram-positive and Gram-negative bacteria, including vancomycin- and methicillin-resistant strains. The antibacterial effects and stability following peptide truncation and D-amino acid substitution were investigated. D-amino acid substitution did not change the antimicrobial activity of PLNC8 αβ, however, it increased the stability of the peptide as it was more resistant to proteolysis by trypsin compared to the native L-enantiomer. Moreover, among the truncated peptides, α1–22, β7–34, and β1–20 retained bacteriostatic effects without displaying bactericidal activity. L-PLNC8 αβ peptides were tested for their antibiofilm properties and displayed rapid disruption of surface-associated S. epidermidis. Electron microscopy shows that PLNC8 αβ targets bacterial cell membranes, ultimately resulting in rapid permeabilization and altered homeostasis, including ATP release. PLNC8 αβ does not show any cytotoxic or hemolytic effects on human cells in vitro. Furthermore, PLNC8 αβ counteracted the cytotoxic effects and expression of inflammatory mediators that were induced by S. aureus, including MMPs and growth factors that are essential in cell regeneration. Pathogen recognition receptors (TLR2, TLR4, and PAR2), intracellular signaling events (c-Jun, c-Fos), and inflammatory mediators (IL-1β, IL-6, CXCL-8), that facilitate pathogen recognition, cell survival, and cellular communication, were all enhanced by the peptides. At sub-MIC concentrations, PLNC8 αβ enhanced the activity of various antibiotics against both Gram-positive and Gram-negative ESKAPE bacteria. In conclusion, plantaricins efficiently impede bacterial pathogens and enhance the activity of antibiotics and thereby constitute a therapeutic option to counter the threatening situation with severe antibiotic-resistant infections.
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| 2. |
- Svärd, Anna, 1985-
(author)
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Novel methods for diagnosis and treatment of periodontal disease
- 2024
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Doctoral thesis (other academic/artistic)abstract
- Periodontitis is an inflammatory condition affecting tooth-supportive structures, the periodontium. Gingival tissues respond to biofilm formation by initiating an inflammatory process. If left untreated, inflammation progresses to a non-reversible condition in susceptible individuals, causing degradation of the underlying bone structures, where teeth become mobile and tooth-loss eventually occurs. Periodontitis is very common, affecting about half of the adult population. The disease is not only a concern for oral health but is linked to many systemic conditions, such as cardiovascular disease, diabetes, rheumatoid arthritis, and Alzheimer’s.The studies included in this thesis aim to develop new strategies for the diagnosis and treatment of periodontal disease. Current diagnostic practices rely on probing and x-ray examination. There is a need for more sophisticated diagnostic tools. We have developed different sensing strategies for detection of a key-pathogen in periodontitis, Porphyromonas gingivalis, and its secreted enzymes, gingipains. The proteolytic activity of this pathogen, which drives the destructive effects of the disease, can be detected at low levels by utilizing gold nanoparticles and nanoplasmonic sensing in different ways.Treatment of periodontitis is basically limited to the removal of soft and hard biofilms. This requires significant resources, from patients as well as clinicians, and maintenance phase is often life-long. We have identified and tested the antibacterial effect of an antimicrobial peptide derived from Lactobacillus plantarum. This bacteriocin, plantaricin NC8αβ, has been shown to effectively inhibit P. gingivalis. The bacteriocin has been further optimized into a short peptide sequence, C5, which can rupture outer membrane vesicles from P. gingivalis. Taken together, these results suggest new sensing strategies for novel diagnostic tools for periodontal disease and define a promising antibacterial agent for periodontal treatment in the future.
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