VPR Microbiology: Virulence Factors PDF

VPRP096 Introduction to Microbiology: Virulence Factors Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Virulence factors Virulence factor Bacterial traits that confer pathogenicity. Virulence factors enable processes such as adhesion,...

VPRP096 Introduction to Microbiology: Virulence Factors Dr. Ricardo Gutiérrez, Microbl., MSc, Ph.D. Assistant Professor [email protected] Spring semester, 2024 Virulence factors Virulence factor Bacterial traits that confer pathogenicity. Virulence factors enable processes such as adhesion, biofilm formation, motility, toxin secretion, immune evasion, colonization, and bacterial cell–cell communication. Allowing bacteria to colonize (extracellular and/or intracellular) niches in hosts and produce disease. Virulence factors Virulence factors Surface-associated proteins Host cell adhesion and colonization Nutrient acquisition Cell invasion and immune evasion Biofilm formation Pili Adhesion DNA uptake DNA transfer Motility Efflux pumps Antibiotic secretion Siderophore secretion Other secretion of toxin compounds Toxin production Tissue damage Invasion Impairs immune response Flagella Quorum-sensing Bacterial cell-cell communication Virulence gene expression control LPS Inflammation Tissue damage Two component system Virulence factor regulation Secretion systems Virulence factor delivery Protein secretion and transport DNA uptake and transfer Motility Host cell adhesion Virulence factors Bartonella infection journey (example) Listeria intracellular infection path in nonphagocytic and phagocytic cells (example) Virulence factors Today’s topics Toxins Capsule Flagella Fimbriae Quorum sensing Biofilm Transfer of VFs Virulence factors Bacterial toxins Virulence factors Bacterial toxins Exo → secreted by the bacteria. Exotoxins are highly antigenic proteins. They are different types of exotoxins according to the mechanisms and targets. A-B toxins Type III toxins Intracellular targets Membranedamaging toxins Superantigens Cell-surface targets Extracellular matrix (EM) toxins EM targets Virulence factors Bacterial toxins A-B toxins Type III toxins They usually modulate the host cell metabolism Virulence factors Bacterial toxins Membrane-damaging toxins Cytotoxic = kills the cell Pore-forming toxins Lipases Virulence factors Bacterial toxins Superantigens Cytokines Trigger excessive stimulation of T lymphocytes. Resulting in massive T-cell proliferation and cytokine release. Fever, arthritis, dermatitis, shock. Virulence factors Bacterial toxins Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. Lack of blood flow means the cells and organs do not get enough oxygen and nutrients to function properly. Many organs can be damaged as a result (organic failure). Virulence factors Bacterial toxins Extracellular matrix (EM) toxins Hyaluronic acids EM : substances or environment between and below cells. Toxins allow free-movement of bacteria Collagen Hyarunidases Collagenases Streptokinase Virulence factors Hey! I heard that before… Slide from lecture ”Bacterial structure” Virulence factors The intravascular release or presence of LPS present massive effects on the hosts, and their impact is concentration dependent. High endotoxin levels can cause shock (organ failure) and intravascular coagulation. Endotoxin in small amounts can induce symptoms of inflammation, fever, and leukopenia, and damage to blood vessels, finally leading to hypotension. Virulence factors Capsule Capsules have a significant role in determining access of certain molecules to the cell membrane, mediating adherence to surfaces, and increasing tolerance of desiccation. Protection against: Virulence factors Flagella Motility Adhesion Participates in biofilm formation Modulate immune system of eukaryotic cells Virulence factors Pili/fimbriae Their presence greatly enhances the bacteria's ability to attach to the host and establish infection. Virulence factors Quorum-sensing Bacterial cell-cell communication by small signal molecules (pheromones, autoinducers) Effect on virulence and other metabolic gene expression control Low density: autoinducers diffuse away from bacteria promoting individual cell behavior High density: autoinducers bind to receptors and promote group behavior When the bacterial population reaches a defined density (a bacterial quorum), the pheromones attain a critical threshold concentration at which they coordinate expression of bacterial genes, so that the colonizing bacteria act as a community rather than as individuals Virulence factors Biofilm formation ▪ Clusters of bacteria that are attached to a surface and/or to each other and embedded in a self-produced matrix ▪ Consists of substances like proteins, polysaccharide and released DNA ▪ Protective organization or arrangement Virulence factors Biofilm formation Virulence factors Transfer of virulence factors (VF) a. Transformation. Bacteria acquire free DNA from the environment. Some of the acquired DNA may be VF genes. b. Transduction. Bacteriophages (viruses of bacteria) transfer bacterial DNA from one bacterium to another. Some of the transferred DNA may be VF genes. c. Conjugation. One bacterium can transfer a plasmid (mobile DNA) to another bacterium. Usually, plasmids contain VF genes. Virulence factors Transfer of virulence factors (VF) Emergence and dissemination of Antimicrobial drug resistance Selection of serious pathogenic strains in the clinics