Biological agents as causes of disease Flashcards
What are the three types of pathogens
obligate pathogens, facultative pathogens, oppurtunistic pathogens
describe obligate pathogens
ONLY survive in host
Describe facultative pathogens
present in the environment - wait for host
Example of facultative pathogens
Salmonella and E.coli
Describe opportunistic pathogens
normally benign but cause disease in compromised host
example of opportunistic pathogens
Legionella
what diseases do bacteria cause
cholera, typhoid & food poisoning
what diseases do eukaryotes cause
malaria and thrush
what diseases do viruses cause
AIDS, small pox and thrush
Where do virulence genes normally cluster
pathogenicity islands
What can carry virulence genes
bacteriophages
TRUE or FALSE - virulence genes can horizontally transfer from bacteriophages
TRUE
Where are virulence genes located in shigella
virulence plasmids
Where are virulence genes located in salmonella
pathogenicity islands
Describe the life cycle of fungi
complex - show dimorphism
How do fungi exhibit dimorphism
grows as mould at low temps, yeast when in lungs
Why is it hard to treat fungal infections
eukaryotic nature and dimorphism
What happens to fungal yeast when its ingested into the lungs
engulfed by macrophages
Example of disease caused by protozoa
malaria
Describe malaria
insects used as vector, switches between human & mosquito host
What are the protective barriers of human body
flora, mucous and epithelia
What are flora
dense epithelia with bacterial & fungal flora
Where is mucous secreted
small intestine and bladder
How do epithelia work as a barrier
tightly packed to prevent entry
What are bacterial effectors
proteins secreted by pathogenic bacteria into host
Where are virulence effector proteins encoded
pathogenicity islands of gram negative bacteria
Example of bacteria with virulence effector proteins
Salmonella
How do virulence effector proteins enter the host
injected into target host cells like intestinal epithelial cells
What do virulence effector proteins do to the host cell
manipulate cellular signalling pathways to establish infections
Name two bacterial features
P Pilli, Adhesins
What is the function of adhesins
allows anchorage to epithelia
Describe the type III secretion system
needle like device that injects virulence effector proteins
What does the type III secretion system create
actin pedestal
What does the type III secretion system allow to enter the cell
toxins and virulence effector proteins
How do effector molecules regulate biological activity
bind to proteins to increase or decrease enzyme activity, gene expression or signalling
What molecule do virulence effector proteins act like
ligands
What does actin polymerisation enable
tight adherence which destroys microvilli
What triggers actin polymerisation
extracellular pathogens
What is intimin
ligand that ONLY interacts with Tir
What is the effect of tir and intimin on the host cells
rearrangement of host cell morphology
How does the actin pedestal cause gastroenteritis
destroys brush border microvilli in intestine
What bacteria typically evades the immune system by hiding in cells
Legionella
How do bacteria evade the immune system
hide in macrophages
What are the two types of actin polymerisation
zipper and trigger
What pathogens use the zipper mode of actin polymerisation
Listeria and yersinia
What pathogens use the trigger mechanism of actin polymerisation
Salmonella and shigella
What happens if Listeria crosses the BBB
causes meningitis
What does listeria secrete
listeriolysin O - protein that breaks down membrane of phagosome
What happens to listeriolysin O once it enters the cytoplasm
mis folds and degrades
Why does listeriolysin O mis-fold in the cytoplasm
pH is too alkali
What is listeriolysin
pore forming toxin
What does listeria bind to to trigger actin polymerisation
e-cadherin
What do antibiotics inhibit
cross linking of peptidoglycan
What do viruses contain
nucleic acid and protein coat
Why do viruses need proteins
replicate and package the genome
What are the 3 stages of the life cycle of a virus
lytic, lysogenic and latent
Describe the lytic stage of a virus
viruses cause cell to burst open
describe the lysogenic stage of
integration of virus DNA into host’s genome
describe the latent stage of virus life cycle
viral genome is quiet and X virus proteins are translated
What is the baltimore classification based on
central dogma that minus sense DNA is transcribed by RNA transcriptase
describe virus class 1
dsDNA virus - same structure as cellular DNA
Examples of diseases caused by viral class 1
herpes, papilloma virus, and adenoviruses
describe viral class 2
ssDNA copied into dsDNA
example of viral class 2
parvovirus
Describe viral class 3
viral enzyme copies ddRNA into mRNA
example of viral class 3
rotavirus
describe viral class 4
(+) ssRNA directly makes viral proteins
example of viral class 4
polio
describe viral class 5
uses RNA polymerase to make mRNA from (-)RNA
What is the product of all the viral classes
mRNA for protein production
example of viral class 5
ebola and influenza
example of viral class 6
AIDS & leukaemia
describe viral class 6
reverse transcriptase enables transcription of (+)RNA into dsDNA
how do viral class 6 make mRNA
incorporated into host chromosome
describe viral class 7
reverse transcriptase converts dsDNA into mRNA
Example of viral class 7
Hepatitis B
What are the four types of viral entry strategy
fusion with PM, fusion with membrane after endocytosis, pore formation, endosomal membrane disruption
What virus fuses with PM as its entry strategy
HIV
What virus fuses with membrane after endocytosis as its entry strategy
influenza
What virus causes pore formation
polio
what virus causes endosomal membrane disruption
adenovirus
How does the viral genome up-regulate
DNA replication & proliferation
How does HPV replicate
has its own chromosome so replicates independently of host
Why does integration of a virus into basal epithelial cause cancer
genome of basal epithelial has lots of proliferation
What is the function of E6 & E7
increase hosts DNA replication machinery
What are E6 & E7
oncoprotein’s that mediate development
How can over expression of E6 & E7 be measured
measure mRNA transcripts
What is the function of Rb & p53
prevent cell growth
How does Rb prevent cell growth
binds to cell proliferation factor keeping it inactive
How dos p53 prevent cell growth
activates safety brakes on cell proliferation
How does E6 & E7 overproduction effect p53 & Rb
binds and inactivates them causing de-regulation
What are proto-oncogenes
oncogenes that are incorporated into the viral genome
what are srcs
proteins involved with cell proliferation
what is c-src
powerful activator of cell growth