Lecture 6: GI 1 Flashcards
what are the three main pathotypes of Escherichia Coli?
Enterotoxigenic (ETEC)
Enteropathogenic (EPEC)
Enterohemorrhagic (EHEC)
Escherchia coli bacteria are gram ______, are ______ anerobes, and move via _______. They are common ______ meaning they are found in the GI tract of normal animals
negative
facultative
flagellae
commensals
how is Escherchia coli transmitted and what is the first step in it’s pathogenesis?
via feal oral route
it colonizes the intestinal mucosa
ETEC is a little different in the way it attaches to the enterocytes in the GI tract compared to EPEC and EHEC. Explain briefly how each type attaches to cells.
ETEC just barely touches the cell and does not intimately bind, then delivers enterotoxins into the cell
EPEC anchors itself to the host cell’s cytoskeleton via intimin/tir receptor and there is actin pedestal formation which provides the bacteria with support. It then uses a type 3 secretion system to inject host cell effector proteins.
EHEC also uses the actin pedastal formation similar to EPEC, but it injects shiga toxins into the host cells
neonatal animals that have diarrhea, especially cattle, are likely to have
ETEC (enterotoxigenic E coli)
an infection with enterotoxigenic E coli may progress so rapdily that….
death occurs before development of diarrhea and is referred to as enteric colibacillosis complicated by shock. this is due to large amounts of LPS by ETECT (lipid A portion most responsible for symptoms of shock)
ETECT produces enterotoxins. There are two major classes, heat stable (ST) and heat labile (STa & STb). Describe how they work
STa: reduce the absroption of elecrolytes and water from the intestine
STb: induces duodenal and jejunal secretion of water and electrolytes
how does EPEC (enteropathogenic E coli) successfully anchor itself to the host cell?
once EPEC forms an actin pedestal, the intimin receptor translocates into the host cell and inserts itself into the host cell plasma membrane, which is all mediated through the T3SS (inject it’s own receptor). This receptor interacts with intimin on the bacterial surface which anchors the bacterium to the host cell.
E coli septicemia can also result from non enteris infections such as:
- umbillical infection of neonates
- urogenital tract infections
- mastitis
- lung infections
how do you diagnose E coli?
- isolation of E coli from feces is not very meaningful because E coli is often found in healthy animals
- it’s better to find the toxins or fimbrial antigens via PCR or monoclonal antibody based techniques
- in cases of septicemia you can culture the blood
_______ is the most common cause of diarrhea in calves less than 10 days old
E coli
ETEC is usually less than 3 days old
EPEC and EHEC usually in slightly older calves, 2-30 days or up to 4 months sometimes
what are som risk factors for developing an E coli infection in cattle?
- failure of passive transfer
- poor hygiene or overcrowding
- inappropriate volume or composition of milk or milk replacer
the E coli vaccine given to cows is initially given to cows how? is there any other options besides the vaccine?
- as two doses, 3 weeks apart, with second dose 3-6 weeks before calving
- there are commercially available antibodies you can put in the milk
_____ is the most important cuase of septicemia in neonatal foals, but less imporant as a primary cause of diarrhea than in calves and pigs
E coli
what is the E coli that infects birds called? what clinical signs will you see in birds? birds that get this are usually associated with what?
APEC (avian pathogenic E coli)
C/S: diarrhea, septicemia, meningitis, polyarthritis, localized infections
- usually associated with poor hygiene (healthy birds are resistant)
Enteric colibacillosis is common in ____. What signs will you see? Which pathotypes cause this?
neonatal piglets
C/S: diarrhea, dehydration, whole liter often affected
ETEC and EHEC
post weaning diarrhea in pigs is caused by what E coli pathotype?
ETEC
What is edema disease and what E coli pathotype causes it? What are some clinical signs?
- a disease secondary to enterotoxemia that occurs inpiglets 1-2 weeks after weaning
- EHEC
C/S: neurologic disease, eyelid and forehead swelling, GI tract edema on necropsy
descibe in detail how Shiga toxins work!
A subunit is associated with a pentamer of B subunits which mediate binding to a specific receptor, Gb3, on the host epithelial or endothelial cells, which allows the toxin to be internalized by receptor mediated endocytosis. The toxin then moves to the golgi, then to the rough endoplasmic reticulum, then into the cytoplasm. Subunit A is cleaved and a resulting A1 unit interacts with ribosomes to inhibit protein synthesis which kills the cell.
in order for a shiga toxin to work, what must be present?
a Gb3 receptor!
shiga toxin producing E coli (STEC) causes 3 big diseases in animals. list them plz and thx
- diarrhea and dysentery in calves
- hemolytic uremic syndrome in dogs
- edema disease in pigs
true or false: STEC are present in the feces of healthy and diarrheal dogs
TRUE GURL GOOD JOB
STEC causes what disease in dogs? Describe the clinical signs?
hemolytic uremic syndrome (HUS)
usually affecting younger dogs, they will have bloody diarrhea followed by thrombocytopenia, microangiopathic anemia, and anuric acute renal failure. They kidneys will show renal proximal tubular necrosis and hemorrhage
STEC causes what disease in pigs? describe the pathogenesis and clinical signs?
edema in pigs
pathogenesis: colonization of the bacteria is dependent on non-intimate adherence of the bacteria to the epithelial cells in the small intestine by F18 pili. The Stx2e toxin is absroped into the bloodstream and damages vascular endothelial cells in target tissues resulting in edema and hemorrhage
what disease does this horse have?
infection with lawsonia intracellularis
