Types of Pathogens Flashcards
what are pathogens?
anything that can cause pathology (could be a bullet), but generally cosnidered biological agents
give 6 examples of pathogens
- viruses
- bacteria
- prions
- protozoans
- helminths (worms)
- fungi
what are prions?
infective proteins
how do prions become prions?
they are normal proteins your cells make, but become misshapen due to improper folding
what do “bad proteins,” prions do?
can bind to normal prions and cause them to be misfolded as well
what does bad prions binding to good prions cause?
bundles of bad proteins that adhere to each other causing fibrils to form
what do fibrils around bundles of bad prions do?
continue to grow to become plaques in neural tissues
how is scrapies caused?
from animal-based protein in sheep feed
what gene actually codes for prions?
PRNP: not an inherited gene though
what are viruses?
protein shells that contain DNA or RNA as their nuclear material (which codes for genes)
how do viruses get into cells?
protein receptors on the surface of virus particles bind with specific host cell surface receptors, which serve as the key admitting the virus into the cell
what do viruses require to replicate (2)
- a host cell
- the host cell’s transcription and translation machinery
what happens once a virus has replicated inside a cell?
the virus lyses the cell to release new virions which go one to infect other cells
do antibiotics work on viruses? what do you need to treat them?
nope; need antivirals
are antivirals useful?
not really because they cost so much to make and viruses mutate so fast anyway they are rendered useless pretty quick
what do we usually use against viruses and why?
vaccines because we can make variations as viral pathogenicity changes and viruses are pretty easy to culture in lab
what drove antiviral reseaarch and how are the drugs developed for it used?
HIV; antivirals for this usually used in combination
how are viruses classified? why?
by the system they infect because they are usually cell specific
how does pathogenicity affect viruses?
the more pathogenic a virus is, the quicker it moves through a population until members of that population either develop immunity or death
what is the red queen hypothesis?
humans are evolving more complex immunity to outsmart pathogens, which then evolve themselves to infect hosts; this leads to a co-evolutionary arms race but pathogens can evolve more quickly because simpler
what are bacteria?
the smallest pathogens considered to be living
what kind of karyote aare bacteria? what does this mean?
prokaryotes, no nucleus but use the same DNA that eukaryotes do
can bacteria replicate on their own? what do they need?
yes, just need nutrients and warmth
how do we treat bacterial infections?
will respond to antibiotics, just need to match for susceptibility
how are most antibiotics made?
from nature, that other bacteria made to kill the competition
what are many bacterial infections secondary to?
viral infections or cute/injury as bacteria take advantage of weakened immunity
what are protozoans?
eukaryotes with a complicated genome in a ture nucleus that are closely related to human DNA
how do we treat protozoal infections?
drugs are difficult since genome is so close to us, but lots of protozoans have symbiotic bacteria inside so we can kill that bacteria to kill the protozoan sometimes
describe protozoal infections compareed to bacterial and viral
tend to be more chronic and long term because many protozoans have complex lifecycles and employ elaborate immune-evasion mechanisms
give 8 examples of protozoan diseases
- toxoplasmosis
- amoebic dysentery
- primary amoebic meningitis
- scours in calve (zoonotic)
- giardia
- leishmania
- african sleeping sickness
- chagas disease
what are helminths? give two types
parasitic worms; paltyhelminths (flatworms) and nematodes (geohelminths)
how long can the disease state from helminths last and why?
can last for many years due to the long life span of the worms in the body
how do helminths evade treatment?
employ elaborate immune-evasion mechanisms
list and describe 2 immune-evasion mechansism employed by helminths
- production of cytokine-like molecules to calm immune response
- molecular mimicry: worms make huma-like proteins to fool the immune system
what are the 2 common routes of transmission of helminths?
- fecal-oral
- boring through skin
what do helminth life cycles usually require?
2 hosts: one invertebrate and one vertebrate
what 2 things are true of helminths who remain in bodues for longer?
the longer the pathogen wants to remain in the body:
1. the greater the immune-evasion mechanisms have to be
2. the less pathology the pathogen seeks to cause (typically)
describe the length of infections by the 4 types of pathogens
- viral infections typically run their course rapidly and resolve
- bacterial infections typically resolve rapidly if treated, if not treated it is up to the immune system to deal with it but drug resistance and genetic recombination can complicate drug therapy
- protists can become chronic, with relapses occurring if host is immune-suppressed
- parasitic worms may be with you for many years (10-20)
as an epidemiologist, what do you need to know about your pathogen?
- all that you can
- especially ALL routes of transmission
