8-2: Microbial Pathogenesis Flashcards
We don’t know about any pathogenic…
Archaea
Vast majority of the microbes we interact with are…
Neutral/beneficial
What is an infection
Invasion of body by a disease-causing organism. Can result in disease
What is a disease
Damage or injury to host organism. Some bacteria cause disease without infection
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
What is an opportunistic pathogen
Organism that is often non-pathogenic, but becomes pathogen under certain circumstances
Symptoms of a bacterial disease are caused by…
Activities of pathogen or immune response to pathogen (fever, rashes, redness, swelling)
Major steps in many infections/microbial diseases
Adherence: binding to specific host cells/tissues
Colonization: expanding population
Invasion: gain access to privileged sites
Spread: move beyond site of initial infection
What is a mucous membrane
Tightly packed epithelial cell layers covered with a mucous layer (protective)
Lines body access points (airways, oral cavity)
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
What is a virulence factor
Molecules produced by a pathogen that contribute to its ability to cause disease
Common types of virulence factors (5)
- Adhesion factors
- Nutrient acquisition
- Immune resistance (help pathogen survive immune defense)
- Immune evasion/disruption
- Extracellular enzymes, protein secretion systems/effectors and toxins
Describe adherence as a virulence factor
Microbes typically target specific cell or tissue type, adherence to specific receptors on those cells is key
Provides foothold, facilitates interaction/invasion of host cells
Examples of adhesins
Pili, fimbriae, surface proteins, capsules
Adherence receptors:
Glycoprotein, glycolipids
How do pathogens evade the immune system
Hide inside cells
Produce capsule to hide surface antigens (prevent immune detection)
Modify antigens e.g. PAMPs such as LPS detected by immune system
What are extracellular enzymes
Secreted/surface enzymes that promote virulence
How do extracellular enzymes promote virulence
Free up nutrients, damage host cells, inactivate immune cell mechanisms, disrupt barriers to enable invasion
Example of secretion system for virulence
Type III secretion system (T3SS)
How do T3SS work
Inject effector proteins into host cells
effectors have specific target to manipulate host cell biology
What are exotoxins
Secreted protein toxins, similar to bacteriocins
