11. microbial pathogenesis I Flashcards
when a micro-organism is growing and multiplying on or within a larger organism, known as the host, it is said to have an ______
infection
this is any change from a state of health in which part or all the host is incapable of carrying on its normal functions due to the presence of a pathogen or its products (toxins)
infectious disease
an organism that causes a disease is known as a ________
pathogen
the ability for a pathogen to cause a disease is called ________
pathogenicity
an organisms _________ is the degree of harm (pathogenicity) inflicted on its host
virulence
what factors does microbial virulence involve?
think “APIT”
- adherence
- persistence
- invasion
- toxigenicity
what are the two types of pathogens
extracellular and intracellular
these are pathogens that grow and multiply within host cells (inside the body cells such as macrophages, neutrophils and tissue cells). they can be subdivided into two groups: facultative and obliagate
intracellular pathogens
these are pathogens that remain in tissues and fluids but never enter host cells
extracellular pathogens
a type of intracellular pathogen that reside within the cells of the host but can also be grown in pure culture without host-cell support (in vitro)
facultative intracellular pathogens
- think can be studied in lab thus “faculty” therefore “facult”ative
a type of intracellular pathogen incapable of growth and multiplication outside the host cell.
obligate intracellular pathogens
true/false: all viruses are obligate intracellular pathogens
true
__________ are examples of protozoa that require host cells (RBC’s) for growth
malarial parasites
this is a micro-organism that does not causes disease
non pathogen
this is an agent capable of causing disease, only when the host’s resistance is impaired (e.g. immunocompromised).
opportunistic pathogen
true/false: opportunistic pathogens can be part of your normal microbiota
true
what are some characteristic of bacteria that are pathogenic?
- aderence
- persistence
- invasion
- toxigenicity
- transmissibility
- ability to survive in the hosts immune system
this scientist proposed a series of postulates that have been applied broadly to link many specific bacterial species with particular diseases
Robert Koch
what are Koch’s postulates
- the microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms
- the microorganism must be isolated from a diseases organisms and grown in pure culture
- the cultured microorganism should cause disease when introduced into a healthy organism
- the microorganism must be preisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
what are Koch’s molecular postulates
- the phenotype or property under investigation should be significantly associated with pathogenic strains of a species and not with nonpathogenic strains
- specific inactivation of the gene or genes associated with the suspected virulence trait should lead to a measurable decrease in pathogenicity or virulence
- reversion or replacement of the mutated gene with the wild-type gene should lead to restoration of pathogenicity or virulence.
this is the location from which the pathogen is transferred to the host
the source of the pathogen
the source of the pathogen can be either _____ (humans or animals) or ______ (water or food)
animate or inanimate
this is the natural environmental location in which the pathogen resides
reservoir
these are diseases where infectious agents are transmitted from animals to humans
zoonoses
what are the four main routes of transmission?
- airborne transmission
- contact transmission
- vehicle transmission
- vector-borne transmission
pregnant women can also pass on a pathogen to their unborn child via this type of transmission
vertical transmission
in this type of transmission, the pathogen is suspended in the air in droplets, aerosols or dust
airborne transmission
true/false: droplets require close proximity for transfer between hosts
true
these are smaller particles, 1 to 5 micrometers in diameter, that result from the evaporation of the larger droplets
aerosols or droplet nuclei
true/false: the influenza and ebola viruses can be transmitted either by droplet or droplet nuclei
false; the influenza virus can, but the Ebola virus can only be transmitted through droplets if the droplets directly contact the potential host’s mucous membranes
this type of transmission implies the coming together or touching of the source or reservoir of the pathogen and the host; can be divided into direct and indirect
contact transmission
a type of contact transmission where an actual physical interaction with the infectious source is needed such as touching, kissing, body contact
direct contact
a type of contact transmission that occurs when an inanimate object transfers the infectious agent between hosts
indirect contact
these are inanimate objects that become colonized with microbes and serve as potential intermediaries for pathogens transmission
formites
this is the transmission of pathogens though inanimate material (vehicles or formites), in which the vehicle spreads the pathogen to multiple hosts.
vehicle transmission
what are some examples of vehicles associated with vehicle transmission
- surgical instruments
- drinking vessels
- stethoscopes
- bedding
- eating utensils
- clothing
these are living transmitters of pathogens
vectors
most vectors are ____ or ______
arthropods (insects, ticks, mites, fleas) or vertebrates (dogs, cats, skunks, bats)
this type of transmission often benefits the pathogen by permitting extensive reproduction and spread within the host
vector-borne transmission
pathogens transmitted by biting arthropods are often highly virulent causing diseases such as
- malaria
- sleeping sickness
- typhus
the _______ of pathogenic bacteria into the body are the sites where mucous membranes meet the skin
portals of entry
what are some portal of entries for pathogens
- respiratory tract
- GI tract (mouth), genital and urinary tracts
- abnormal areas (e.g. cuts, burns, etc.)