Lecture 10 part 2 -- e.coli, shigella, salmonella Flashcards
what is the most common form of EHEC, responsible for most outbreaks of E. coli?
E. coli serovar O157:H7
what is the major disease caused by EHEC?
explain it
mild to moderate colitis
we need less than 100 of EHEC bacteria to get colitis. this is why its the cause of a lot of outbreaks
the specific disease is called Hemolytic Uremic Syndrome (HUS)
it damages glomerular vessels, causes acute renal failure, thrombocytopenia, and CNS issues
can EHEC get into the bloodstream?
the shiga toxin is what gets into the bloodstream to cause a variety of issues like renal failure and CNS issues
what is the toxin of EHEC
shiga toxin (Stx)
how are EHEC and EPEC similar?
they both produce A/E lesions (pedestals) in the host cell
explain how the shiga toxin works.
which strain of e. coli has shiga toxin
EHEC
it is an AB exotoxin.
the B subunit binds Gb3 glycolipid
the A subunit blocks ribosomal 28S RNA which results in NO PROTEIN TRANSLATION by the host
EAEC stands for what?
what kind of diarrhea does it cause?
enteroaggregative e. coli
causes protracted (long duration) of watery diarrhea
besides EHEC, what other strain of E. coli produces shiga toxin? what does this mean?
EAEC also produces shiga toxin
this means it also causes HUS (hemolytic uremic syndrome)
O:157H:7 is the strain of EHEC that causes most disease.
what is the most common form of EAEC that can also cause HUS?
O104:H4
explain how EAEC work.
what is their adhesion protein?
adhesion protein = AAFI (aggregative adherence fimbriae I) which tightly binds to intestinal mucosa to form a “stacked brick” arrangement.
this stimulate mucus secretion to PROTECT THEMSELVES and a thick biofilm forms following QUORUM SENSING
how can shigella get into our body?
through FECAL ORAL route – humans are the only reservoir
true or false
all shigella serotypes have an exotoxin and it is the shigella toxin
yes
there are over _______ serovars of salmonella
over 2000
do shigella bacteria have pilli?
NO but they have adhesins
do salmonella have pilli?
YES – type 1 pilli
What are the 2 main diseases caused by all types of Shigella bacteria
Dysentery (intestinal infection) and HUS (hemolytic uremic syndrome)
Shigella bacteria are biochemical variants of _____
E. coli (specifically EIEC – enteroinvasive E. coli)
what are the 2 most relevant shigella species? which is the most common? which is the most severe?
shigella sonnei and shigella dysenteriae
more common = shigella sonnei
more severe = shigella dysenteriae
how is shigella transmitted
ONLY fecal-oral route
humans are the only reservoir
what is very unique about shigella
they replicate INTRACELLULAR and spread through cell-cell passage to avoid immune detection and clearance
true or false
shigella infections spread easily throughout the body
FALSE – they are usually in a confined location. they move by moving to each individual neighboring cell
shigella bacteria attach, invade, and replicate in cells lining the ____
colon
what are the primary virulence factors of shigella
ipas – invasion plasmid antigens. injected through a type III secretion system
shiga toxin – disrupts protein synthesis, leading to intestinal epithelial cell damage.
B subunit binds Gb3 (glycolipid) on the host cell
A subunit cleaves 28s rRNA to prevent tRNA from binding to the “A” site of the ribosome
how does shigella bacteria spread from cell to cell?
actin polymerization
there are more than _____ unique serotypes for salmonella enterica
2500 (very common like e. coli)
what are the 2 important salmonella human pathogenic serotypes?
salmonella typhi and salmonella paratyphi
how is salmonella transmitted?
-ingestion of contaminated food
-fecal-oral route
name a defining structural characteristic of a salmonella infection
formation of a pedestal that looks like a RUFFLE under a microscope
how do shigella and salmonella have similar replication mechanisms?
they both replicate intracellularly
true or false
SALMONELLA can cause either a transient or chronic infection
true
how does salmonella get into the intestinal tissues?
through M cells
does salmonella get into the blood?
YES
it is transocytised (ie: moves across the entire host cell to get into blood) and gets into the blood/lymph
how does salmonella migrate and colonize efficiently
due to their pathogenicity islands I and II
explain salmonellas pathogenicity island I
encodes for salmonella secreted invasion proteins (Ssps)
explain salmonella pathogenicity island II
encodes for a type III secretion system to secrete various proteins and toxins
name the clinical diseases caused by salmonella
MOST COMMON = gastroenteritis
septicemia
enteric fever
ASYMPTOMATIC COLONIZATION
As mentioned, salmonella can cause septicemia.
who is most at risk for this
young, elderly, and immunocompromised
typhoid fever is another word for
enteric fever
explain how enteric fever happens
caused by salmonella
initial bacteremia with subsequent colonization of the GALLBLADDER and then REINFECTION of the intestines
which bacteria can have ASYMPTOMATIC colonization
salmonells
