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64 Cards in this Set
- Front
- Back
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What makes E. coli famous?
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Its the predominant facultative anaerobe in the colon normal flora
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What are 2 flavors of E. coli?
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Pathogenic and nonpathogenic
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Can nonpathogenic E coli cause infections?
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YES
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What are 2 situations in which E. coli causes infections?
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-Debilitated or immunosuppressed
-GI barriers breached |
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What are the 3 clinical syndromes pathogenic E. coli cause?
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-UTI
-Sepsis/meningitis -Enteric diarrhea |
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How many types of enteric diarrheal diseases do pathogenic E. coli cause?
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6
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Gram stain morphology of E. coli:
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gram neg bacillus
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Biochemical id of E. coli:
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Glu/Lac fermentor
Gas producer Indole pos H2S nonproducer |
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Is E. coli motile?
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Yes
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What is a method of identifying different strains of E. coli?
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Kauffman serotyping
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What are the 4 serotype groups of E. coli?
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HOKF
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What does HOKF stand for?
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H = flagella antigen
O = somatic antigen K = capsular antigen F = Fimbrial antigen |
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What is the O somatic antigen?
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LPS - oligosaccharide
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What is the K capsular antigen?
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Acidic polysaccharide
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How many UTIs are caused by E. coli?
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90% the majority
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What E. coli strain causes UTI?
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UPEC - uropathogenic
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Where are UPECs normal flora?
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In the colon
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What are the 3 levels of UTI caused by E. coli?
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-Bacteriuria
-Cystitis -Pyelonephritis |
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What is the virulence factor that UPEC uses to cause Cystitis?
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Type I pili - FimH, an adhesin
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What does the FimH type I pili on UPEC bind to?
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Uroplakins on the lumenal surface of the bladder.
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What virulence factor does UPEC use to cause Pyelonephritis?
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P pili
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What does the P pili on UPEC bind to to cause pyelonephritis?
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Glycolipids on RBCs and Kidney cells
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What are Uroplakins? What binds to them again?
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Mannose containing cell surface glycoproteins; that's what the FimH type I pili bind to in cystitis.
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What type of molecule is FimH?
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An adhesin
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So the 2 adhesins associated with cystitis are:
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-FimH
-Uroplakin |
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What adhesins area associated with Pyelonephritis?
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-P pili (pyeloneph assoc; PAP)
-Glycolipid on RBC/kidney cells |
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How do UPECs survive the acidic pH and urine flow of the urinary tract?
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By residing WITHIN cells
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What is the bladder's response to UPEC infection?
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Exfoliation
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How does a chronic UTI develop?
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-overexfoliation=chronic damage
-bacteria survive in pods in the bladder |
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What is the virulence factor on 80% of E. coli strains causing Neonatal Meningitis?
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K1 capsular polysaccharide
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What does the capsule contribute to developing neonatal meningitis?
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-Resistance to phagocytosis
-Resistance to complement |
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Where are K1 isolates normally found?
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In the colon
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Why does K1 cause meningitis?
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It has antigenic mimicry with Fetal Neonatal Neuronal tissues.
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What is K1 immunologically and chemically identical to?
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The capsule polysaccharide of N. meningitidis group B
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What is the determining factor for whether E. coli or strep pneumo will cause neonatal meningitis? Which is more virulent?
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The magnitude of bacteremia.
Strep pneumo is more virulent - takes fewer bugs to cause it. |
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What do ALL E.COLI causing diarrhea have at lease one of?
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A virulence determinant carried on a plasmid.
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How are chromosomal virulence determinants organized?
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Into pathogenicity islands - clusters of genes.
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What are individual virulence traits encoded on?
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-Transposons (ST)
or -Phage (Stx2) |
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What are the 3 mechanisms by which E. coli causes diarrhea?
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1. Enterotoxin production
2. Intimate adherence and membrane signalling 3. Intracellular invasion |
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What are the 2 types of Ecoli that have intimate adherence and membrane signalling?
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-EPEC - pathogenic
-EHEC - hemorrhagic |
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What is the Ecoli type that causes intracellular invasion?
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EIEC - invasive
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What type of diarrhea do you see in ETEC infections?
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WATERY with no blood
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What are the common cases of ETEC?
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-Traveler's diarrhea
-Pediatric diarrhea in developing countries |
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What is the infectious dose of ETEC?
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HIGH
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How is ETEC transmitted?
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In contaminated food and water
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What are the 2 methods of treatment for ETEC?
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-Maintain hydration
-Antibiotics may shorten duration |
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How is ETEC diagnosed?
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-Bioassays
-Immunoassay -Toxin gene probe |
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Where do the enterotoxigenic E. coli set up colonies?
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In the small bowel
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What are the toxins expressed by ETEC strains?
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-Labile toxin
-Stabile toxin |
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What is Labile toxin 80% identical to?
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Cholera toxin
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What is Labile Toxin's structure?
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-5 identical B subunits
-1 A subunit |
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To what cell surface marker are the B subunits specific?
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GM1
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What happens when labile toxin binds a host enterocyte?
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It gets endocytosed, degraded, and A subunit is released into the cytosol.
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What is the action of A subunit of stabile toxin?
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ADP-ribosylation of Gs
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What is Gs?
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The stimulatory subunit of adenylate cyclase.
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What happens when Gs is ADP-ribosylated?
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It activates adenylate cyclase which increases intracellular cAMP
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What is the result of increased cAMP?
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-CFTR is activated to release Cl which is a diuretic
-NaCl absorption is inhibited |
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How does the structure of ST compare to LT?
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It is a monomer that contains multiple cysteines
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What is the result of ST containing multiple cysteines?
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It resists heat denaturation
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What is ST encoded on?
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Plasmids and Transposons
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What does ST do?
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Binds guanylate cyclase and stimulates cGMP production
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What is the result of cGMP production?
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CFTR activation, Cl- secretion
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So is ST-induced diarrhea distinguishable from LT-induced?
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no
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Do ETECs only produce ST or LT?
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No; some produce both, in which case symptoms are worse.
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