Lecture 23: Micro-organisms in Disease: Infection 1 Flashcards
What is Pathogenicity?
The capacity of a micro-organism to cause infection
What are the requirements of pathogenicity?
Transmissibility
Establishment in or on a host
Harmful effect(s)
Persistence
What is harm often mediated by?
Harm is often mediated by host response, rather than by the pathogen itself
What is virulence?
May be used interchangeably to describe pathogenicity
Virulence sometimes defined as the degree to which a micro-organism is able to cause disease.
Allows a relative description of pathogenic potential
What is Infectivity?
The ability of a micro-organism to become established on/in a host
What is infectivity mediated by?
Microbial ligand
Host cell surface receptor
What is virulence factor?
Components of a microorganism which aid its ability to cause infection (infectivity and virulence). Encoded by virulence genes.
What are some examples of virulence factor?
Facilitation of adhesion
Toxic effect(s)
Tissue-damage
Interference with host defence mechanisms
Facilitation of invasion
Modulation of the host cytokine responses
True or false: All fungi are eukaryotic?
True
What makes up the wall that most fungi possess?
Chitin
Name the tree types of disease causing fungi?
- Yeast
- Filamentous (moulds)
- Dimorphic (Yeast and mould)
What is Oral candidiasis (Thrush) an example of?
Dysbiosis fungi (Halfway between yeast and mould)
What is found within a yeast cell?
Membrane
Nucleus
Mitochondria
Cell wall (Chitin)
Bud scar
Lipid granule
Vacuole
What common infections do mould cause?
Ringworm
Athletes foot
3What uncommon infections do moulds cause?
Severe infections such as:
Aspergillosis (Infection of lung)
Mucormycosis
How do mould replicate?
Sexual or asexual
(Based on spores)
What occurs during germination spores?
Mycelia form
If the two mating types are close in proximity, extensions called gametangia form between them
What occurs during plasmogamy?
Fusion between mating types results in a zygosporangium with multiple haploid nuclei.
The zygosporangium forms a thick, protective coat.
What happens during Karyogamy?
The nuclei fuses to form a zygote with multiple diploid nuclei
What happens during meiosis and germination?
A sporangium grows on a short stalk.
Haploid spores are formed inside.
What are the two types of parasites?
- Protozoa (Protists) - Unicellular
- Helminths (Worms) - Multicellular
How do parasites replicate?
Can be complex
Sexually or asexually
May require multiple hosts to complete cycle
May include cyst formations as a mode of survival
What are viruses?
Obligate intracellular parasites
Nucleic acid core wrapped in a protein coat (Some have a lipid envelope)
Every class of organism suffers from virus infection
What are the 6 stages of the virus lifecycle?
- Attachment
2.Penetration
3.Uncoating
4.Release - Assembly
- Biosynthesis
What happens during the attachment phase of the virus lifecycle?
virus becomes attached to a target epithelial cell
What happens during the penetration phase of the virus lifecycle?
The cell engulfs the virus by endocytosis
What happens during the uncoating phase of the virus lifecycle?
Viral contents are released
What happens during the release phase of the virus lifecycle?
New viral particles are made and released into the extracellular fluid. The cell, which is not killed in the process continues to make new viruses.
What happens during the assembly phase of the virus lifecycle?
New phage particles are absorbed
What happens during the biosynthesis phase of the virus lifecycle?
Viral RNA enters the nucleus where it is replicated by the viral RNA polymerase.
What is 2 things produced by early virus proteins?
Polymerase
Integrase
What are Prions?
Misfolded proteins, with no genetic material
How do prions arise?
Can be inherited, spread via contaminated material or occur spontaneously
