Chapter 12 - Infectious diseases Flashcards
(46 cards)
infectious
Caused by an invading pathogen and able to be transferred from one organism to another (communicable)
pathogen
a disease causing agent
host
An organism that is infected by a pathogen
infection
the invasion of host by a pathogen, where it establishes itself and replicates
micro organism
a microscopic organism (eg bacteria). Not a pathogen unless it causes a disease
how do scientists identify diseases (Koch’s postulates)
- The potential pathogen must always be present when the disease occurs
- The organism can be isolated from the host and grown in pure culture
- When organisms from the pure culture are inoculated into healthy, susceptible host and the disease develops
- The organism can then be re-isolated, grown in pure culture and compared with the organism first injected for confirmation
how are Koch’s postulates limited
as he only investigated bacterial pathogens and some harmless bacteria may acquire extra virulence factors that make them pathogenic.
Virulence
measure of the ability of a pathogen to cause severe disease within its host
infectious agent
A disease causing agent that can be transmitted from one organism to another
what are the four most common pathogen groups
- Virus: a non cellular pathogenic agent, containing either DNA or RNA, that can only reproduce inside a living host cell
- Bacteria: Prokaryotic, microscopic unicellular organisms that do not have a nuclear membrane or membrane bound organelles,
- Fungi: A diverse kingdom of spore producing eukaryotic organisms, have a cell wall made of chitin, do not possess chloroplasts, have complex cell cycle, in which spores can develop into hyphae then grow into a mycelium, can be unicellular but mostly multicellular
- Protists: An organism that is eukaryotic but may have plant-animal or fungus like features. Usually unicellular
Gall
a brown, roughened lump of undifferentiated tissue on the crown of a plant (where roots meet stem or branch meets trunk) looks tumour like
Transmission
transport of a pathogen from an infected host or reservoir to a susceptible host
Contagious
Able to be transferred by direct contact
Zoonotic diseases
a disease that animals pass to humans. An infection that is naturally transmitted between other vertebrate animals and humans
reservoir
An organism or habitat in which a pathogen can reside, and sometimes replicate, prior to entering a susceptible host. A reservoir is somewhere in which the pathogen does not go extinct
vector
An agent that transmits pathogens from one host to another
Pathogenicity
The capacity of a pathogen to cause disease in a host
three virulence factors that determine the pathogenicity of an organism
- The ability to stick to or invade a particular cell type
- Produce toxins
- cope with or avoid the host immune system
Susceptibility
The likelihood of developing a disease. If the susceptibility of an organism is high, its ability to resist the disease is low
incubation period
The time between infection and the onset of symptoms. Eg, pathogen may have to divide many times to reach numbers sufficient to cause disease or may take time to reach target tissues.
what are the three factors that transmission of infectious diseases depends on
The infectious agent, a susceptible host and a mode of transmission
what are the reason for an incubation period
- The pathogen may have to divide many times to reach numbers sufficient to cause disease
- May take time to reach the target tissues that are susceptible to that particular pathogen
- Toxins produced by bacteria as waste products of metabolic activity may take time to accumulate to level that affects the host
What are viruses
Viruses are non cellular pathogens consisting of one or more strands of RNA or DNA inside a protein coat. Viruses are not made out of cells and therefore are non living. They posses no metabolic machinery for processes such as cellular respiration. Cannot be classified as prokaryotes or eukaryotes
nucleic acid
The molecule (DNA or RNA) that forms the genetic code in an organism
