lecture 1 Flashcards
what are Koch’s postulates?
set of criteria used for the identification of microorganisms involved in disease
-discovery of tb, anthrax, cholera
what does each of Koch’s postulates state?
1: microbe should be found in all cases of the disease
2: should be able to extract the microbe and grow it in pure culture
3: when introduced into susceptible host, will cause the same disease
4: when you extract the microbe from the susceptible host, should be the same strain originally found
what is gastritis and peptic ulcers
inflammation of the inside of the lining of the stomach
open sores on the protecting lining (gastric ulcer) & upper portion of the small intestine (duodenal ulcer)
how do proton pump inhibitors work?
stop the pumps in the stomach that pump acid into the stomach–> can help heal the ulcers
high relapse rate tho
what was the successful culture for Marshall?
leaving plates for a longer time in reduced oxygen levels
Marshalls publication found that the bacilli were ___ shaped and were gram ____, _____, and ___.
what genus was the species in?
spiral or curved
negative, flagellate, microaerophillic
Campylobacter
Marshall could not find a good animal model, so?
After he had gastritis, he?
drank a culture of H. pylori
recovered the bacterium, treated with antibiotic + proton pump
what is the best treatment for peptic ulcer disease?
antibiotics–> eliminated inflammation, prevent replapse
+ acid secretion inhibitor
how does H pylori colonize the stomach with urease and what does ammonia do?
– generates ammonia + Co2–> increase pH
–ammonia reduces viscosity of mucus, which makes it easier to penetrate
–flagella and helical shape helps it move
how does H pylori cause stomach ulcers?
why is it a carcinogen?
toxins damage goblet cells, which produce mucus
decrease in mucus leads to no protection from stomach acids—> ulcer formation
persistent inflammation can lead to development of cancer
what are weaknesses to Koch’s postulates?
what were the revisions made to help accommodate these?
-some infected animal/ people are asymptomatic
-not all pathogens can be cultured in lab
-some pathogens only infect humans
use human cell culture
use human organoids (mini organs from stem cells)
use PCR to determine presence of microbe
what are the pros and cons of using insects, nematode, fish?
pros: less ethical concerns, lower costs, larger number of hosts, easier maintenance
cons: not as closely related to people as non human mammals
what are ways to determine the effect of pathogens
signs
Ld50– dose of pathogen required to kill 50% of infected animals
histology– staining of tissue & determine alteration by microscopy & bacteria present
determine # of bacteria in diff organs
how does Ld50 work?
divide mice into several groups
inoculate each group with a diff dose number
more lethal— needs less amount of pathogen to kill half of the animals
what are the stage of bacterial pathogenesis and what are asymptomatic and symptomatic
bacterial exposure–> colonization (asymptomatic)
immune evasion–> infection (symptomatic)
what is adherence and what does it allow microbes to do? examples?
attach & bind to a niche (like attach to a tissue)
allows bacteria to avoid host clearance mechanisms
UTI, tears, saliva, mucus
what are adhesins?
allow bacteria to attach to host cells receptor, surface proteins, capsules—> like pili
binding is specific
what are other functions of receptors other than then adhesions attaching to them?
are glycolipids or glycoproteins
can dictate tissue or host tropism of the pathogen
what is colonization of bacteria? what changes?
establishment of bacteria at a site, involves adherence AND growth
undergo change in gene expression and metabolism
growth as biofilms
what is bacterial motility? why would they want to move?
flagella helps it move – long helical thing
spins like a propellers to move cell
can sense chemicals and move bc of that OR nutrients may attract them
where is an example where flagella is important?
in UTI, good for traveling form urethra to the kidney, which can lead to pyelonephritis and can lead to bacteremia
what is invasion of bacteria and why they do it?
cross the epithelial Barrier– usually mucus membrane
get access to nutrients,
avoid antimicrobial systems
avoid competing with other microbes
what is the zipper active mechanism of invasion in gram pos bacteria ?
1: internalins on gram pos pathogens bind receptors on host cells
2: actin is recruited–> leading to remodeling of the plasma membrane (zipper like)—> and bacterial engulfments thru endocytosis
what is the type 3 secretion system in gram neg bacteria, salmonella?
1: injectisome contacts the host cell
2: delivers effector proteins into the host
3: target singalling pathways that alter actin structure
