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what is the systemic manifestation of gram negative?
Toxic shock ( it needs high bacterial burden)
what is generally initiated by LPS and endotoxin?
activation of complement
release of cytokines
decrease in peripheral circulation
shock and death
what does septic shock cause?
what are some factors associated with pathogenesis of enterobacteriae?
Exotoxin ( not in opportunistic E.coli)
> Stx-1,2 ( shiga toxin)
> LT 1 ( like chlorea toxin)
specific virulence factors for other pathogenic members
what types of infections do entrobacteriae group cause generally?
what is the difference between opportunistic and pathogenic?
opportunistic are usually part of normal microflora ( escherchia/ klebsiella)
pathogenic are not ( shigella, salmonella, yersenia, and some escherchia)
Neonatal meningitis :
E.coli and group B strep cause majority of CNS infection in < 1 month infants
75% E.coli are K-1 serotype
EC-k-1 is commonly presented in GI tract of pregnant woman
immediate treatment of infant with IV antibiotic ( penicilin and aminoglycoside)
what is gasteroenteritis by E.coli defined by?
it is defined by serotype of e.coli not a part of common microflora
how many strains are there causing gasteroenteritis:
Some characteristics of EPEC strain are:
uncommon in Us
Cause watery diarrhea in infants
cause A/E lesions similar to STEC
what are some virulence factors associated with EPEC?
BFp bundel forming pili
Intimin ( adhessin)
TIR ( equivalent unknown for STEC)
Some of characteristic of ETEC are:
very common in developing countries ( mostly infants and travelers )
Infection via ingestion of contaminated food and water
what are some symptoms associated with ETEC?
watery diarrhea , cramp vomit, develope after 1.2 days and persist for 3.4 days
what are some virulence factors associated with ETEC?
Heat stable and labile
exotoxin stimulate hypersecretion of fluids and electrolytes.
both toxins are A-B subunit toxins
either toxin sufficient to cause symptoms
fimbreae which is important for adherence
what are some ways to treat ETEC
Cook , boil and peel
water and electrolytes
some characteristics associated with EHEC and STEC
most common in developed countries
more than 50 serotypes and most common in STEC o157:h7
cause bloody diarrhea
what are some ways of transmission EHEC=STEC
low infection dose ( less than 100)
most common during warm days in children under 5
contaminated , undercooked meat and raw vegetables
Disease associated with EHEC= STEC
uncomplicated diarrhea to hemorrhagic colitis
initial watery ( 3.4 days)
in young children severe complication
what is hemolytic uremic syndrome associated with
it is associated with shiga toxin 2 producing strain
acute renal failure leading to death
what are some virulence factors associated with STEC/EHEC
they induce A/E lesions as do EPEC
Expression of shigella toxin 1 and 2
Toxin acquired by bacteriophage
toxin binds to receptor found on endothelial cells of intestine and kidneys
induce cell death ( inhibition of protein synthesis)
isoform of Slt2 binds preferentially to renal endothelial and associated with HUS
what are some diagnostic ways for EHEC
most o157 don't ferment sorbitol ( sorbitol mcConkey is used for stool samples)
** there is a drawback since some ferment sorbitol and also this method does not assess toxin production
stool sample on mcConkey and analyze colonies for toxin production ( PCR)
what are treatments for EHEC?
water and electrolytes for treating symptoms
antibiotic not recommended since it may prolong the disease
wash, boil, cook and peel