Lecture 10-E coli Flashcards
What are the characteristics of E coli?
- gram neg
- motile
- non sporulating
- rod shaped
- facultative anaerobe
- part of normal microbial population of intestinal track of humans and other warm blooded animals
How may E coli be categorized?
into diff types of pathotypes base on their ability to produce toxins, adhere to epithelial cells and ability to invade epithelial cells
the pathogenic traits of E coli have mostly been acquired through?
horizontal gene transfer
E coli is differentiated into serotypes based on what 3 major surface antigens?
O (LPS), H(flagella) and K (capsule)
The ___ antigen defines the serogroup of a strain and the ___antigen identifies the serotype
O and H
___ has the ability to form distinctive lesions on the surface of intestinal epithelial cells
Enteropathogenic E coli (EPEC)
EPEC is only transmitted via ___
fecal oral route, humans the only carrier, environmental reservoirs have not been identified.
T or F: EPEC generally has enterotoxins
F
What is the mechanism of diarrhea production by EPEC?
so there is obvious deformation of the enterocyte cells (effacement of microvilli) but the exact production of diarrhea production is not understood for EPEC. the effacement of microvilli may lead to a decrease in absorptive surfaces thereby contributing to diarrhea by increasing water in the small intestine. Tight junctions also disrupted = increased intestinal permeability.
__ can cause mild to bloody diarrhea and haemolytic uremic syndrome
STEC
what is HUS? how is it caused
haemolytic uremic syndrome. It is caused by the destruction of red blood cells. The damaged red blood cells clog the filtering system in the kidneys which can lead to life threatening kidney failure.
most common serovar for STEC is
O157:H7
transmission for shiga toxin producing E coli occurs via the
fecal oral route (cattle); lysogenic phage thereafter
Why are antibiotics not recommended to treat STEC?
Stx toxin are carried on lysogenic phage which may become lytic during bacterial stress, antibiotics cause stress and therefore are not recommended; under stress it can affect other strains of E coli that dont naturally have the shiga toxin so you would be spreading it even more.
EIEC and ___ are facultative intracellular pathogens
Shigella
explain how infection may occur for by EIEC -shigella.
- they are invasive and divide in the intracellular milieu of intestinal cells
- infection is a multistep process, cells penetrate the epithelial barrier, induce macrophage cell death, invade intestinal epithelial cells, engagement of intra and intercellular movement and degrade epithelial integrity.
- destabilize the tight junctions and induce epithelial cell death.
The massive inflammatory response is associated with ____ and ____ and leads to ____ (characteristic of EIEC/shigella)
- apoptotic macrophages and EIEC invasion perforates the epithelial barrier and leads to tissue lesions.
what are some symptoms of EIEC shigella
- mild watery diarrheal, fatigue, malaise, fever and anorexia.
- later in the disease there may be abdominal cramps, blood and mucus in the diarrheal and dehydration
- HUS can also occur
what are some effective treatments for EIEC/shigella ?
oral rehydration (think diarrhea, antibiotics to shorten duration of illness)
T or F: unlike STEC, antibiotics seem to protect against HUS with EIEC/shigella
True
- Common in North America
- May be the most common bacterial pathogen identified in patients with diarrheal
- found in calves, piglets and horses
- transmitted through food and water contaminated with fecal matter
Enteroaggregative E coli (EAEC)
There exists great variability in virulence factors and toxins between EAEC strains, but a three part infection model is characteristic of EAEC infection. What are they?
- cells adhere to intestinal mucosa
- cells produce enterotoxins and cytotoxins
- mucosa becomes inflamed due to toxins and the immune system
The identifying factor of EAEC strains is….
pAA virulence plasmid.
a very diverse pathotype and major cause of travelers diarrhea and endemic in most underdeveloped countries
ETEC- enterotoxinogenic E coli
can produce either or both heat labile or heat stable enterotoxins and produce several colonization factors for adherence to intestinal epithelium
ETEC
what is the MOST defining characteristic of ETEC
it is the only Ecoli to have a heat stable toxin
The heat stable toxin in ETEC works by ___
inducing chloride and fluid secretion into the lumen thus diarrhea
ETEC exposure occurs via___
the fecal oral route, exposure from contaminated food and drinking water.
Symptoms of ETEC and potential treatments include
symptoms: mild-severe (non bloody) diarrhea –> dehydration, headaches, fever, abdominal cramping, nausea and vomiting. very rapid onset, duration illness 3-5 days
treatment: hydration, electrolyte
DAEC stands for
Diffusely adherent E coli
What is special about the way DAEC cause infection?
- They attach to epithelial cells but don’t follow the classical pattern of adherence such as attachment and effacement of microvilli. Adherence of DAEC occurs over the entire surface for the epithelial cells.
what happens when DAEC bind to epithelial cells?
- induce actin rearrangement and destroy the microvilli, tight junctions become leaky
what is the recommended treatment for DAEC
oral rehydration because several strains are already resistant to most antibiotics
causative agent of crohns disease
adherent invasive Ecoli
___ and ___ are extracellular pathogens that attach to intestinal epithelium and efface microvilli forming characteristic A/E lesions
EPEC and Lee positive STEC
___ uses colonization factors for attachment to host intestinal cells
ETEC
___ forms biofilms on the intestinal mucose and bacteria adhere to eachother as well as to the cell surface to form an aggregative adherence pattern (AA) known as stacked brick
EAEC
___ is dispersed over the surfaces of intestinal cells, resulting in diffuse adherence (DA) pattern
DAEC
___ colonizes the intestinal mucosa of patients with Crohns disease and is capable of invading epithelial cells as well as replicating within macrophages
AIEC (adherent invasive)
_____ are intracellular pathogens that penetrate the intestinal epithelium through __ cells to gain acess to the ___.
EIEC/shigella, M cells, submucosa
EIEC - Shigella escape submucosal macrophages by ___ followed by ____
induction of macrophage cell death, followed by basolateral invasion of colonocytes and lateral spread.
Lee genes lead to what? these are found in?
effacement of microvilli and EPEC + STEC
ETEC isolates carry what enterotoxins
LT and ST solely together on plasmids.
DAEC isolates have ____ that enhance adherence called the Afa/Dr
fimbrae
EAEC virulence factors are foiund on the ____
pAA plasmid
T or F: genes involved in the pathogenesis of AIEC strains are unclear
T
__ gained the ability to invade cells mainly through the pINV plasmid and acquired additional virulence traits in the form of PAIs
EIEC/shigella
important virulence factors include genes that encode the ability to
- adhere to epithelial cells
- produce toxins
- invade epithelial cells
In food, the common E coli pathotypes are ___, ___, ___ and ___
STEC, ETEC, EAEC and EIEC
