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Toxic Shock Syndrome and Other Related Severe Infections
Published in Botros Rizk, A. Mostafa Borahay, Abdel Maguid Ramzy, Clinical Diagnosis and Management of Gynecologic Emergencies, 2020
C. septicum is a gram positive bacterium that distinguishes itself from its relatives by its relative aerotolerance, a quality that allows it to infect tissues independent of trauma. C. septicum produces four toxins, called α-, β-, δ-, and γ-toxins [35]. Of these, α-toxin is responsible for the cytotoxic effects of C. septicum. First released as an inactive prototoxin, α-toxin is later converted to an active cytolysin that vacuolates and lyses cells. The toxin forms ion-permeable channels in membrane lipid bilayers that induce rapid outflow in potassium, adenosine triphosphate (ATP) depletion, and cell necrosis [36]. This α-toxin is ushered into tissues by additional enzymes including a hyaluronidase, fibrinolysin, deoxyribonuclease, and hemolysins.
Enterococcus: An Important Opportunistic Pathogen—Basic and Clinical Aspects
Published in Dongyou Liu, Handbook of Foodborne Diseases, 2018
Karen Flores-Moreno, Claudia Mayoral-Teran, Yolanda Lopez-Vidal
Cytolysin. Cytolysin is a secretory virulence factor identified in E. faecalis. Its secretion is variable among E. faecalis strains. The operon responsible for its production has been described on both the chromosome and the plasmid, and its production can be self-induced by quorum sensing. The cytolysin function is mainly lysis erythrocyte cell, although it can also lyse some leukocytes.14
Vibrio: Caenorhabditis elegans as a Laboratory Model for Vibrio Infections
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
Sellegounder Durai, Krishnaswamy Balamurugan
Studies with C. elegans and Vibrio spp. started with the most dreadful pathogen V. cholerae.106 In the marine environment, the bacterium secretes well-characterized toxins including cholera toxin (CT) and toxin coregulated pili (Tcp). Bacterial cell-to-cell communication has a major role in regulating the virulence of the bacterium.107 Studies with C. elegans shed light on the V. cholerae metalloprotease prtV, which is involved in establishing infection in higher vertebrates, and this also proved by studying its effect on a monolayer of mammalian intestinal cell lines. Since this protein (PrtV) is found to be essential for infection in humans and C. elegans, the results support the use of C. elegans as model to study V. cholera infection.1 Another study explored V. cholerae cytolysin (VCC), which is one among the accessory V. cholerae virulence factors that may contribute to disease pathogenesis in humans. VCC, encoded by hlyA gene, belongs to the most common class of bacterial toxins known as pore-forming toxins (PFTs). V. cholerae infects and kills C. elegans in a cholerae-toxin-independent manner. VCC is required for lethality, growth retardation, and intestinal cell vacuolation during infection. A microarray analysis was performed in C. elegans exposed to V. cholerae strains with intact and deleted hlyA genes. Many of the VCC-regulated genes identified, including C-type lectins, Prion-like (glutamine [Q]/asparagine [N]-rich)-domain containing genes, genes regulated by insulin/IGF-1-mediated signaling (IIS) pathway, were previously reported as mediators of innate immune response against other bacteria in C. elegans. The protective function of the subset of the genes upregulated by VCC was confirmed using RNAi. By means of a machine learning algorithm called FastMEDUSA, the study identified several putative VCC-induced immune regulatory transcriptional factors and transcription factor binding motifs. Results from the experiments suggest that VCC induces a wide variety of immune-response-related genes during V. cholerae infection in C. elegans.108
Gram-negative quorum sensing signalling enhances biofilm formation and virulence traits in gram-positive pathogen Enterococcus faecalis
Published in Journal of Oral Microbiology, 2023
Ana Parga, Daniel Manoil, Malin Brundin, Ana Otero, Georgios N. Belibasakis
Three transcripts representative of the two quorum sensing systems best described in E. faecalis were assessed, operons fsr and cyl. The main operon, fsr, encodes a two-component system that senses cell density and regulates virulence. The transmembrane histidine kinase, fsrC, senses the presence of gelatinase-biosynthesis activating pheromone (GBAP) and activates the transcription factor, fsrA. Downstream genes include fsrC itself, and transcripts encoding the membrane protein FsrB and the pro-peptide FsrD. FsrD is the precursor of GBAP, generated after processing by FsrB [26]. Herein, fsrC was up-regulated by 2.4-fold in strain ATCC 29212 after exposure to short-chain AHLs. Similarly, fsrC displayed a 3.3-fold up-regulation in strain UmID7 after exposure to long-chain AHLs (Figure 4a). On the other hand, the cytolysin operon regulates the production of a lantibiotic that results from the pore-forming activity of CylLL and CylLS. These peptides require post-translation modifications by CylM and CylA to be active [26]. Herein, the cyl operon was only present in strain ATCC 29212. Among the two genes assessed, cylM and cylA, the latter displayed a 2.8-fold up-regulation after exposure to long-chain AHLs (Figure 4b).
Dual functions of discoidinolysin, a cholesterol-dependent cytolysin with N-terminal discoidin domain produced from Streptococcus mitis strain Nm-76
Published in Journal of Oral Microbiology, 2022
Atsushi Tabata, Airi Matsumoto, Ai Fujimoto, Kazuto Ohkura, Takuya Ikeda, Hiroki Oda, Shuto Yokohata, Miho Kobayashi, Toshifumi Tomoyasu, Ayuko Takao, Hisashi Ohkuni, Hideaki Nagamune
In the present study, we investigated the molecular characteristics of the novel CDC, discoidinolysin (DLY), produced by S. mitis strain Nm-76 (Figure 1). Previously reported CDCs produced by S. mitis strains include MLY [38], Sm-hPAF [40], and LLY [41]. In addition, Morales et al. reported the presence of genes encoding LLY-related proteins in several strains of S. mitis [29]. One of the genes, designated llyA2 by the authors, displayed homology to the dly in S. mitis Nm-76 introduced in this study. However, production of the transcribed product from llyA2-positive strains has not yet been confirmed, and the molecular characteristics of the llyA2 product remain unclear. Another lly related gene, llyB, has also been reported [29]. However, the product of llyB is not cytolysin but rather an adhesion molecule named mitilectin (MLC) [49]. The nomenclature of LLYA2 seems unsuitable for systematically distinguishing the dly/llyA2 gene product from Sm-hPAF/LLY and LLYB/MLC. Therefore, in the present study, we designated the novel CDC found in S. mitis strain Nm-76 as DLY and performed molecular characterization of DLY.
Surface properties of Enterococcus faecalis cells isolated from chicken hearts determine their low ability to form biofilms
Published in Biofouling, 2018
Jolanta Cieśla, Dagmara Stępień-Pyśniak, Agnieszka Nawrocka, Małgorzata Łukowska, Tomasz Hauschild, Andrzej Wernicki, Andrzej Bieganowski
Among the strains that were analysed, only E. faecalis (ATCC 29212) showed negative results for the β-galactosidase and lactose tests and, additionally, completely destroyed the blood cells (β-haemolysis). This is linked to the production and extracellular secretion of certain substances. One such substances is cytolysin/haemolysin, which displays both haemolytic and bactericidal activities towards a number of eukaryotic cell types, including macrophages and polymorphonuclear neutrophils, as well as Gram-positive bacteria (Libertin et al. 1992). Another substance, gelatinase, is an extracellular zinc endopeptidase that hydrolyses collagen, gelatine, and small peptides and has been shown to exacerbate endocarditis in an animal model. The production of these substances may potentially contribute to virulence in enterococci (Toğay et al. 2010).