ID 2 Flashcards
WHat is a pathogen?
A microbe that causes disease
What is a pathogen that does not cause disease/harm?
Commensal
What is a saprophyte?
An organism that feeds on and decomposes dead organic matter
What is bacteraemia?
A pathogen in the blood stream
What is septicaemia?
Blood poisoning
What is infection
Pathogens entering and colonising in host tissues
What is an infectious disease?
A disease caused by a pathogen entering and colonising in host tissues
Host pathogen relationships are dynamic. What does this mean?
They can modify each other’s activities
What are pathogen determinants? Give examples
Any genetic/biochemical/structure that enables it to produce disease in a host
Virulence, entry route, host immune response, environment stability, infective dose
What are host determinants? Give examples
A variable that can affect the frequency of disease within a population
Age, gender, species, immune strength (opportunistic), genes
Pathogenesis is the mechanism that leads to disease. Describe this process
Host is exposed to pathogen
Pathogen adheres to skin or mucosa
Pathogen enters invades through the epithelium
Pathogen forms colony, produces virulence factors and grows
Further growth at new sites
Cause tissue damage and disease
WHat are the 2 ways that virulence factors cause pathogenesis?
Promote damage
Promote colonisation
What is a virulence factor
A molecule that increases the ability of a pathogen to cause infection
What are exo and endotoxins?
Exotoxins produced by bacteria and released outside of cell
Endotoxins produced by bacteria and released inside cell
What are the 3 types of exotoxins
Neurotoxins (brain)
Enterotoxins (GI)
Cytotoxins (all tissues)
What are Koch’s postulates? No need to list them
4 criteria which establish a microbe as being the cause of a diseasee
List Koch’s postulates
Microbe must be found in all sites and cases of disease
Microbe must be isolated from individual and placed in pure culture
Microbe must cause disease symptoms when inoculated into a new person
Microbe must be reisolated from intentionally infected host
Virulence factors are identified by Falkow’s adaptation of Koch’s postulates. What are these:
Phenotype under investigation must be associated with pathogen
Inactivation of gene associated with pathogen should decrease virulence and pathogenicity
Reactivation of gene associated with pathogen should restore virulence and pathogenicity
What are vaccinations?
Treatment given to produce immunity by stimulating the production of antibodies
Protect individuals, reduce transmission and infection
What are the advantages disadvantages of live vaccinations?
Returning to virulence Not allowed during pregnancy Long lasting Oral/nasal/parental Cheap
What are the advantages and disadvantages of killed/attenuated vaccines?
Expensive Injected/parenteral routs Ok for pregnancy Need multiple doses Short lasting
What is a recombinant vaccine?
Treatment to stimulate immune response, made by inserting DNA that codes for an antigen into another’s DNA molecule
What is a subunit vaccine?
Vaccine constructed from antigenic components of a pathogen e.g. proteins
What is an antitoxin vaccine?
Vaccine against a toxin a pathogen produces, rather than the pathogen itself
WHat is sterile immunity?
Complete prevention of an infection
What is the immunological method used by vaccines?
Antigens recognised and phagocytosed
presenting of antigens on surface to T cells
T cells produce clones - T cells, helper, killer
T cells activate B cells which divide to plasma cells
What is the difference between cell mediated response and humoral response? In immunity
Cells themselves destroy pathogen e.g. cytotoxic T cells, phagocytes
Humoral - produce antibodies to destroy the pathogen
