8-2: Microbial Pathogenesis Flashcards
Which domain of life lacks pathogenic organisms?
Archaea! (or at least, we don’t know any yet)
What are phytopathogens?
Microbial pathogens that target plants. Eg. Erwinia amylovora which targets apples.
What are more common than bacterial pathogens targeting plants?
Fungal pathogens, eg. fusarium oxysporum, causing Panama disease in the Gros Michel bana
What is Dutch Elm Disease>
Fungal pathogen carried by bark beetles from asia.
What is an infection
Invasion of body by a disease-causing organism. Can result in disease, but not the same thing as disease.
What is a disease
Damage or injury to host organism. Some bacteria cause disease without infection (using toxins).
What is a pathogen
An organism that causes disease
What is pathogenesis
Mechanism that leads to disease
What is virulence
Similar to pathogenesis, used to describe the severity of the disease. Eg. “highly virulent”
What is an opportunistic pathogen
Organism that is often non-pathogenic, but becomes pathogen under certain circumstances
What are symptoms of a bacterial disease are caused by?
Activities of pathogen (eg. toxins, tissue damage) or immune response to pathogens (fever, rashes, redness, swelling)
What are the 4 major steps in many infections/microbial diseases?
Adherence: binding to specific host cells/tissues
Colonization: expanding population (planktonic or biofilm)
Invasion: gain access to privileged sites through mucous membranes
Spread: move beyond site of initial infection
What is a mucous membrane
Tightly packed epithelial cell layers covered with a protective mucous layer. Lines body access points (airways, oral cavity and GI).
What is invasion
Ability of pathogen to enter host cells and/or tissues. Penetrate beyond where microbes usually reside
Strategies of invasion
Entering host cells, damaging epithelial layers
How does S. pyogenes invade cells?
Secreting enzyme called hyluranidase that degrades hyluronic acid, disrupting the epithelial layer.
What is a virulence factor
Molecules produced by a pathogen that contribute to its ability to cause disease
What are some common types of virulence factors? (5)
- Adhesion factors
- Nutrient acquisition (eg. iron sideophores)
- Immune resistance (resistance to ROS)
- Immune evasion/disruption (hide from immune system)
- Extracellular enzymes, protein secretion systems/effectors and toxins (damage host)
Describe adherence as a virulence factor
Microbes typically target specific cell or tissue type by adhering to specific receptors on those cells.
Provides foothold, facilitates interaction/invasion of host cells
What are some examples of adherence factors? (adhesins)
Pili, fimbriae, surface proteins, capsules
What are some common adherence receptors?
Glycoprotein, glycolipids
How do pathogens evade the immune system
Hide inside cells
Produce capsule to hide surface antigens
Modify antigens e.g. pathogen associated molecular patterns (PAMPs) like LPS that are detected by immune system
How do extracellular enzymes promote virulence
Free up nutrients, damage host cells, inactivate immune cell mechanisms, disrupt barriers to enable invasion
Give two examples of extracellular enzymes.
S. aureus and coagulase, S. pyogenes and streptokinase
