Microbes 2 Flashcards
What is commensal flora?
Organisms found in ecological niches of the body which generally have a symbiotic relationship
What is a pathogen?
Microorganisms which cause disease
What is a primary pathogen?
Pathogens which overcome host defences to cause disease
What is an opportunistic pathogen?
Normal flora causing disease when normal host defences are broken down
What is infection?
Process of microbial invasion of the body
What is infectious?
A pathogen which can be spread from person to person
What is pathogenicity?
Capacity of a microbe to cause damage in a host
What is virulence?
Degree of pathology caused by an organism
What are the 6 stages of pathogenesis?
- Entry
- Attachment
- Multiplication
- Evasion of host defences
- Causes damage
- Release and spread
What is the main difference between gram-positive and gram-negative bacteria?
Gram-positive organisms have a thick peptidoglycan layer and no lipopolysaccharide and lipoprotein
What is a mycobacteria?
Bacteria containing a mycolic acid layer and arabinogalactan
Where is genetic material found in viruses?
Capsid
What does the genetic material and capsid make up?
Nucleocapsid
What 5 things are viruses classified by?
- Symmetry
- Enveloped or not
- Nucleic acid type
- Number of nucleic acid strands
- Polarity
Give 5 steps of infection of host cells by viruses
- Virus attaches to target cell epithelium
- Cell engulfs virus by endocytosis
- Viral contents are released and viral RNA enters nucleus
- Viral mRNA is used to make viral proteins
- New viral proteins are made and released into ECF
How does a virus attach to a target cell epithelium?
Attaches to a specific receptor cell through attachment proteins in capsid or glycoproteins in virus envelope
What 2 ways can a vrius enter the cell?
- Endocytosis
2. Fusion of viral envelope and cell membrane
Describe the replication mechanism for a DNA virus
Use host proteins and enzymes to transcribe DNA into mRNA to make proteins
Describe the replication mechanism for a RNA virus
Use RNA core to directly synthesise mRNA which directs host cells to synthesise viral enzymes and proteins
What are 4 effects of viruses on host cells?
- Lytic infection
- Persistent infection
- Latent infection
- Transforming infection
What is lytic infection?
Death of host cell and release of new viral particles
What is an example of lytic infection?
Polio virus or influenza virus
What is persistent infection?
Cells remain alive and continue to release viral particles, where an infected person can act as a symptomless carrier
What is an example of persistent infection?
Hepatitis B
What is latent infection?
Virus remain quiescent and nucleic acid persists in the cell but mature viral particles are undetected. No viral replication occurs unless triggers
What is an example of latent infection?
Herpes viruses or retroviruses