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The Challenge of Parasite Control
Published in Eric S. Loker, Bruce V. Hofkin, Parasitology, 2023
Eric S. Loker, Bruce V. Hofkin
Several newer vaccine types have been developed, some of which are acellular vaccines in that they do not include whole organisms. An example is the subunit vaccine, in which the vaccine consists of particular immunostimulatory antigens only. The hepatitis B vaccine, for instance, is composed only of viral surface proteins. Our understanding of the stimulatory role of T cells in a humoral response has resulted in the development of conjugate vaccines (Figure 9.28). These vaccines rely on a combination of antigens that stimulate both B and T cells. The Haemophilus influenzae vaccine, for instance, combines polysaccharides found in the bacterial capsule with peptides recognized by antigen-specific T cells. The result is a much stronger antibody response then could be elicited with the polysaccharides alone. And most recently, used clinically only since late 2020, are the mRNA vaccines used against the SARS-CoV-2 virus that causes Covid-19. These vaccines consist of viral mRNA that encodes an antigenic viral peptide. The RNA is surrounded by a lipid-based vesicle, which fuses with host cells, allowing the RNA to enter these cells. The viral mRNA is subsequently translated by host translation machinery and the resulting viral peptide is released from the cell where it stimulates an immune response. See the web callout associated with this section to learn about other vaccine types, including those based on nucleic acid.
Preservatives and Preservation
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Specific, purpose-added ingredients inadequate as preservatives are known to facilitate effective preservation. The chelator EDTA is very effective as preservative adjunct. Although it does not possess stand-alone efficacy, EDTA adds significantly to the efficacy of preservative systems and can be found in many cosmetic products. In this context, it is presumed not only to sequester divalent cations necessary for microbial stability and metabolism, but also to destabilize bacterial capsules and biofilm, allowing better access of the preservative to the biological active (17,109,110). Other chelators such as phytic acid (hinokitol) and gluconolactone presumably offer similar effect (111,112) though the literature offers no compelling data regarding impact on efficacy. Similarly, the efficacy of pyrithione antimicrobials is at least in part associated with divalent cation sequestration (113). In addition to chelators, ingredient such as anisic and levulinic acids, ethyl hexyl glycerine, essential oils, and low levels of ethanol are used as preservative adjuncts (76,114,115,116). General formulation elements contributing to mitigated microbiological risks are also detailed in the relevant ISO guideline (117).
Medical Management for Rhinosinusitis
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Treatment aimed at reducing microbial load or eradicating pathogens from the sinuses assumes that these play a role in causing or propagating CRS. Bacteria may play a role in acute infective exacerbations. Bacterial capsules and exotoxin may trigger an inflammatory response, while superantigens (predominantly Staphylococcal) and fungi may induce eosinophilic inflammation. The organisms isolated from patients with CRS differ from those in ARS, with Staphylococcus aureus, S. epidermidis, and anaerobic and Gram-negative bacteria predominating. Some, such as S. epidermidis are likely to be innocent colonizers. Polymicrobia is common. S. aureus may be isolated in up to 50% of CRSwNP, and MRSA is being increasingly grown, with more than 40% S. aureus cultures in the US now resistant to methicillin. Anaerobes are identified in 14–93% cultures, and may be involved in acute exacerbations.
Mini-review: efficacy of lytic bacteriophages on multispecies biofilms
Published in Biofouling, 2019
Legesse Geredew Kifelew, James G. Mitchell, Peter Speck
The mechanism by which phage spreads through biofilms and how they kill their hosts appears to be that lytic phages encode or stimulate their hosts to produce EPS-degrading enzymes, which facilitate their movement through biofilms (Sutherland et al. 2004). Then, phages move through biofilms, proliferate within their host bacteria, and finally eliminate their hosts via lytic activity (Zhang et al. 2014; Gilbert et al. 2002) as illustrated in Figure 1. Some phages carry genes to encode production of enzymes by the host bacteria that degrade bacterial capsules and other EPS; for example Bacillus subtilis phage ΦNIT1 encodes a monomeric 25-kDa degradation enzyme (designated γ-PGA hydrolase, PghP) to break down poly-γ-glutamate (γ-PGA) - a host capsular polypeptide of glutamate with a γ-linkage, so that phage progenies easily infect encapsulated cells (Kimura and Itoh 2003). However, phage adsorption and proliferation does depend on the growth phase of the bacterial host. Phage entry and multiplication will be enhanced when phages are applied during an exponential growth phase of the bacteria. But dormant and dead host cells will make it difficult for the phages to migrate through and multiply in the biofilm that may lead to abortive infection. This difficulty will be exacerbated if these dead and dormant host cells are present in large numbers (Hu et al. 2012).
Abundant production of exopolysaccharide by EAEC strains enhances the formation of bacterial biofilms in contaminated sprouts
Published in Gut Microbes, 2018
Quintin Borgersen, David T. Bolick, Glynis L. Kolling, Matthew Aijuka, Fernando Ruiz-Perez, Richard L. Guerrant, James P. Nataro, Araceli E. Santiago
Virulence factors associated with EAEC strains include the AraC family regulator AggR9 and its regulon,10-13 serine protease autotransporters (Pic, SepA and SigA)14-17 and, potentially extracellular polysaccharides.18-22E. coli extracellular polysaccharides are mainly found in the bacterial capsule (K antigens),23-25 released as slime into the medium (exopolysaccharide [EPS]),26,27 or attached to the lipopolysaccharide (O antigen)28-31 of E. coli strains. Four loci have been implicated in EAEC 042 polysaccharide synthesis32: wzzB-wza (Ec042_2270 – Ec042_2299), kpsF-kpsM (Ec042_3230 – Ec042_3240), and two copies of the shf locus, which encodes a homolog of IcaB protein of Staphylococcus epidermidis and it is implicated in adhesion and LPS modification (Ec042_4769 – Ec042_4772 and Ec042_pAA021 – Ec042_pAA023).
Development of Lactobacillus kimchicus DCY51T-mediated gold nanoparticles for delivery of ginsenoside compound K: in vitro photothermal effects and apoptosis detection in cancer cells
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2019
Yeon-Ju Kim, Haribalan Perumalsamy, Josua Markus, Sri Renukadevi Balusamy, Chao Wang, Seong Ho Kang, Seungah Lee, Sang Yong Park, Sung Kim, Verónica Castro-Aceituno, Seung Hyun Kim, Deok Chun Yang
In summary, this study highlights the development of ginsenoside CK-gold nanocarriers (DCY51T-AuCKNps) via an intracellular membrane-bound mechanism by lactic acid-producing Lactobacillus kimchicus DCY51T. Ginsenoside CK was effectively loaded onto the surface of gold nanoparticles by non-covalent conjugation such as, electrostatic forces, hydrogen bonding, hydrophobic forces and van der Waals interactions. Upon further investigation by HR-TEM, the particles were formed in the bacterial capsule and cell wall than on the cytoplasmic membrane, possibly due to reduction of the metal ions by enzymes and EPSs present in the cell wall and slime layer. The drug loading efficiency was determined to be ∼11.03%. The FTIR spectra of DCY51T-AuCKNps demonstrated the presence of alkane (C–H) bending and ether (C–O) stretching of ginsenoside CK, further confirming the direct complexation of ginsenoside to the surface of nanoparticles. The in vitro stability of DCY51T-AuNps and DCY51T-AuCKNps demonstrated their resistance to aggregation and dissociation caused by pH variation or a high ionic strength environment. Although DCY51T-AuCKNps demonstrated greater cell inhibition in RAW264.7 cells at 10–20 µM of equivalent ginsenoside CK concentration compared to A549 and HT29 cells at the same concentrations, preferential cytotoxicity of DCY51T-AuCKNps against A549 cells and HT29 compared to free ginsenoside CK was demonstrated by MTT assays. Increased apoptosis of DCY51T-AuCKNps in cancer cells compared to cell apoptosis count in RAW264.7 cells and DCY51T-AuNps-treated cells at sublethal concentrations was confirmed by Hoechst staining with excitations by laser. These results suggest that DCY51T-AuCKNps are promising drug delivery platforms for cancer therapy as novel photothermal and chemotherapeutic agents.