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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?
- Urinary tract
- wound infection
- gasterointestinal disorder
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
- severity varies
- 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
- prefered method
- 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
- cook meat
- wash, boil, cook and peel
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