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52 Cards in this Set

  • Front
  • Back
part of our normal flora and the most common opportunistic pathogen
e. coli
four disease that E. coli can cause
1. gastrointestinal infections
2. UTI
3. bateremia
4. maningitis
three characteristics of E. coli that contribute to its pathogenicity
1. K1 capsule (serum resistance)
2. Pili (UPEC)
3. shiga-like (cause of Gi symptoms)
causes 95% of all non-hospital acquired UTIs
E. coli
Many UTI bacteria are capable of binding
mannosides - common constituents of uroepithelial cells and UTI
and are either mannose sensitive or not
an infection with UPEC is considered an infection when there is how much bacteria in urine
10 to the 5 / ml
a term used to describe the syndrome involving dysuria (burning feeling during urination), urgency, and occasionally suprapubic tenderness

usually involves lower urinary tract
resuts from urinary tract infection that has disseminated to kidney - flank pain, tenderness, and feer, dysuria, etc
acute pylenophritis
binds glycolipis on uroepithelial cells and erythrocytes and encoded by the pap operon
associated with E. coli
P pili (MR = mannonse resitant)
stochastic switching of phenotypic trait to provide phenotypic diversity inside and outside the host
phase variation - E. coli associated with UTI

controlled by variety of mechanism strand slippage, methylation, recombination, influenced by enviromental factos
neo-natal meningitis
20% - 40% of individuals care a type of E.coli that can colonize a new born via vertical transmission -
E.coli has resistance due to the KI capsule -

crosses BBB to survive in CSF, proliferate, and cause tissue damage
E. coli associated bacteremia - often has serum resitance due to the production of
K1 capsule

K1 capsule is made of sialic acids which are like host glycoproteins. the capsule is like that of neisseria meningitidis
leading cause of nosocomial bacteremia
E. coli - crosses from UT tract ot blood
e.coli has what kind of gram stain
Gram negative
Klebsiella pneumoniae has what kind of gram stain
gram neg opportunistic
how does the klebsiella pneumoniae's capsule contribute to the increased pathogenicity
1. reduced phagocytosis
2. reduced complement susceptibility
what is used to help identify K. pneumoniae based on mucoid colony

the capsule decreases phagocytosis and complement activation
differs from Klebsiella in that it is motile and generally less heavily encapsulated
enterbacter cloacae
does e. cloace cause diarrhea?
the two characteristic that are known to contribute to pathogenicity of proteu vulgaris
1. flagella
2. urease synthesis
infections are seen secondary to broad spectrum antibiotic therapy or secondary to instrumentaiton - pneumonia is often contracted after use of contaminated respirator
serratia marcessens
serratia is different from the other enterobacteriaceae in that it is
less likely to colonize GI tract and more assocaiated with respiratory and urinary tract (GI tract is imporatant reservoir among neonates)
produces Ig-specific protease that influence pathogenicity

also associated with septic arthritis
three acute infections caused by p. aeruginosa
1. bacteremia in immune compormised patients
2. eye infections
3. burn infections
associate with Cystic fibrosis where pts are mor susceptible to a chronic bacterial infections
p. auruginosa
cannot ferment sugars. requires aerobic incubation. can grow via anaerobic respiration with nitrate as an electron acceptor, or ferment amino acid arginine
p. aeruginosa
ExoA exotoxin
ADP-ribosylates elongation factor 2 (EF-2) which stops protein synthesis and elicits apoptosis of affected cells - P. aerugosa
these are ADP-ribosylating enzymes that targes host regulatory proteisn and is secreted P. aeruganosa
ExoS and ExoT
cytotoxic exotoxin which ahs phospholipase activity; causes irreversible damage to cellular membranes and rapid necrotic death
ExoU - P. auruginosa
secretes elastase and phopholipases which breaks down elastin and phospholipids in lung surfactant in host cell membranes
p. aeruginoa
most frequently found in the water of cooling towers, resides w/in free-living amoeba
Legionella pneumophilia
sLegionella pneumophilia causes
Legionella pneumonia exhibits what kind of growh t
intracellular and parasitism in amoebae
transmission of Legionella pneumophilia
airborn route from enviroment not from infected people
Diagnosis of L. pneumonnia
diret flourescnet Ab test in sputum -
3 gram negative opportunistic pathogens which are lactose fermenting
E. coli
K. pneumonia
E. cloacae
why is p. aeruginosa described as obligate aerobe
it does not ferment sugars - but can grow nitrate as an alternative alectron acceptor and grow on arginine fermentatively.
3 surface determinants of E. coli
LPS (O-antigen)
Flagella (H antigen)
Capsule (K antigen)
virulence factors which are encoded on a plasmid in E. coli

Heat labile toxin (LT)
heat stable (ST)
verotxin secreted by E.coli is also called
shiga-like toxin

encoded on a lysogenic phage - interferes w/ protein synthesis via RNA cleavage (subunit A) and impacts cytoskeleton (subunit B)
causes HUS (hemolytic uremic syndrome)
seen in about 7% of E. coli infections

hemolytic anemia, thrombocytopenia, acute renal failure etc..
E. coli O157:H7 is a serotype which what kind of diarrhea
bloody due to the shiga-like toxin
shows Type III secretion system
E. coli - enterohemorrhagic ecoli
pathogenenicity island which encodes the T3SSS, intimin, and tir

it is the locus for enterocyte effaceement

seen in enterohemorrhagic E.coli
locus for enterocyte efacement

"pathogeniccity island"
EsB: pores in eukaryotic membrane
EsA: type III filmaments
TIR: E.Coli attachment
Intimin: tiR binding protien on surface
- these are effector protiens, LEE also involves a secretion apparatus
involved in T3SS : allows for E coli attachment
how does the T3SS system work
protein moves across bacterial cytoplasm and outer membrane AND across host cell membrane through a needle into host cytoplasm
shiga-like toxin secreted by and encoded on

how does it work
secreted by E. coli

encoded on phage

intrerferes with protein synthesis via its RNA cleavage activity (subunit A) and may impact cytoskeleton (subunity B)
Hemolysin secreed by enterhemmorhagic E.coli does what
nutrient acquisition by by cytotoxic-pore formation in cells
how does Sorbitol MacConkey Agar distinguis between commensal E. coli and O157:H7
O157:H7 is sorbitol-negative while commensal E.coli are sorbitol-positive
are E. coli, salmonella shigella all lactose what
E. coli is lact +
salmonella and shigella is Lac -

good diagnostic test
what is the serologic test for O157
direct or latex agglutination test

or H7 seology an dtoxin

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