Diarrheas presenting +/- fever Flashcards
Shiga(Vero)-Toxin E. Coli (STEC) includes ??
FYI: Shiga toxin (Stx) = Verotoxin
EHEC: Enterohemorrhagic E. coli O157:H7 (the only sorbitol-negative STEC)
STEC/VTEC strains ???
causes ???
characterized by ??
O157:H7, O104:H4 (Germany), O26, O145
cause GI illness and HUS in young kiddos
hemolytic anemia, thrombocytopenia, acute renal failure (5-14% VTEC inf)
Plotkin’s EHEC scenario
petting zoo–>bloody diarrhea–>given abx–>exacerbated!–>needs dialysis bc of renal failure–>tonic clonic seizures–>HUS
HUS
can cause??
mostly in who ??
implicated strain ?? linked to ??
other strains ??
RBCs are destroyed, kidneys fail, thrombocytopenia
HTN, proteinuria, chronic renal failure, CNS symps
in 5% affected pts, mostly kiddos
ETEC agent
Stx is a ?? that binds ??
non-invasive E. coli, lysogenized by B-tox phage encoding a shiga toxin (Stx):
cytotoxin that binds globotriaosylceramide
VTEC cases in US: strains?
O157:H7 (known as EHEC)
also O111
>100 ww that cause HUS
German outbreak
O104:H4 in bean sprouts
new type of STEC: combo of EAEC and Stx production
EHEC reservoir/transmission
low or high dose org??
zoonosis beef and raw milk (cows eat contam. apples on ground)
low dose (50-500!) organism
person-person transmission happens!!
BUT mountain pk if educated, range (propagated) if poor personal hygiene
EHEC affects who ??
kiddos and oldies more affected
EHEC seasonality
risks
summer, risk for under grilled hamburgs
unpast. juices, milk, bean sprouts, poor personal hygiene
EHEC duration
but young kiddos may still poop org out for..
may resolve in 5-10 days
up to 2 weeks!
STEC/EHEC virulence factors
pili: adherence Shiga toxin (Stx) production
ingested EHEC adheres to ?? and then ??
colonic mucosa
produces Stx
main targets of Stx
gut, kidney, brain
–>produces HUS if gets into circulation (5-10% pts)
abx for STEC and EHEC and EAEC?
NO, associated with significantly higher risk for HUS development
–>release of bac cell-assoc. Stx and induces toxin gene expression (SOS response)
why can some EHEC strains cause HUS ??
able to adhere more tightly to intestinal mucosa
EAEC (Enteroaggregative E. coli) is a bad combo with
Stx–>high rate HUS in German outbreak
EAEC adhere avidly to intestine–>form biofilm
typically persistent diarrhea
human host adapted (vs. EHEC-zoonotic) so human fecal contamination
EHEC presentation
invasive?
fever?
diarrhea that becomes BLOODY 1-3 after onset
may have cramps, N/V
NONINVASIVE (unlike Shigella)
fever in less than 50%, only 1/3 have fecal leukocytes
commonly as AFEBRILE BLOODY DIARRHEA
EHEC dx
routine bac Cx on sorbitol-containing medium
assay for Shiga toxins (ID STEC)
Cx on MacConkey agar with sorbitol (not lactose)
EHEC on MacConkey agar
will be WHITE: sorbitol negative (other STECs and EAEC are sorbitol postitive-pink)
confirm EHEC dx with
serotyping (O157:H7)
ELISA for Stx in poop
PCR (alternative)
labs in HUS
anemia azotemia (N in blood) dec. haptoglobin elev. CRP, LDH, WBCs (leukocytosis), reticulocytes (mod) hematuria/proteinuria on UA hemolysis on PBS: burr, helmets neg. Coombs' stool + for Stx (O157:H7) thrombocytopenia: count
EHEC tx
supportive tx ONLY
abx do not shorten course and may inc. risk for HUS
if HUS happens and no Stx ??
defect in alternative complement pathway
ddx HUS
acute abdomen acute gastroenteritis aapendicitis colitis DIC IBD intussucsception lupus TTP pancreatitis chemo agents: mitomycin, cisplatin, bleomycin, gemcitabine
entamoeba histolytica
invasive eukaryotic protozoan
trophozoite: lack mitochondria, anaerobe, needs large amounts of iron to survive
entamoeba ?? to in order to survive
ingest RBCs
ddx entamoeba from E. coli and E. hartmanni
ddx entamoeba from E. dispar
nuclear morphology and/or size and presence of ingested RBCs
electrophoretic isoenzyme patterns (zymodemes) as they are morphologically identical
entamoeba infectious form
survives where?
cyst
can survive in moist soil or water >1 wk
not killed by normal levels of chlorine
entamoeba can be killed by..
boiling, desiccation, light, heat, 200 ppm iodine
entamoeba occurs where? in who??
developing countries
US: immigrants, travelers, oral-anal sex
entamoeba reservoir
low or high infectious dose??
transmitted how??
*only humans!* low infectious dose: 10^3 (average), 1 cyst can cause disease! fecal-oral rough food and water as vehicles oral-anal sex
entamoeba age, gender, seasonality assoc.
NONE
entamoeba risk factors
low SES
travel to endemic areas
closed populations
promiscuitey
entamoeba is ingested as ??
reaches small bowel and ???
which travel to ??
and form ??
cyst
excyst: release of eight amoebae
travel to large bowel
form mature cysts
entamoeba ??? adhere to colonic epithelium via this virulence factor
trophozoites
adhesins
entamoeba invade the epithelium via ?? and proceed ??
soluble cytotoxins: EC proteases that degrade elastase and collagen
proceed laterally cell-to-cell
entamoeba: cell destruction occurs with formation of ?? surrounded by ?? (which implies what)
discrete ulcers “flasks”
normal appearing intestinal mucosa, suggesting little/no inflammation
entamoeba soluble cytotoxins also ?? which is responsible for the lack of inflammation and few WBCs in feces
kill PMNS on contact
entamoeba virulence factors that degrades C3a and C5a
cysteine protease
entamoeba vir factor: galactose-specific lectin
inhibits complement lysis at C8 and C9 assembly into MAC: Ag similarity btw adhesion and CD59 (human inhib. of assembly of comp. C8 and C9)
entamoeba vir fax: monocyte locomotion inhibition factor
inhibits monocyte migration and blocks respiratory burst of both macros and PMNs
entamoeba presentation
fever?
diffuse abd. pain, profuse bloody diarrhea (wide variation)
with or without fever
> 75% have this if entamoeba inf left untx ??
liver abscess and colonic perforation
duration of entamoeba if left untx?
> 3 wks
wl, abd pain
acute amoebic colitis
fever?
bloody diarrhea, loose, intermittent, watery stool
abd. pain RLQ, abd. tenderness, urgency to defecate
33% have fever and constitutional symptoms
fulminant colitis seen in who?
prevalence of entamoeba cases ?
uncommon presentation seen most in kiddos
3-4%
ameboma (entamoeba) occurs in 1% of those with ??
presents as a ?? and does not respond well to ??
intestinal disease
mass lesion
antiparasite therapy
extraintestinal amebiasis: amebic liver abscess
organism ascends what vein??
present with ??
most common extraint. manifest
ascends portal vein
necrotic abscess, RUQ pain, fever, pleuritic pain
most frequent complication of amebic liver abscess (extraintestinal amebiasis) ???
via contiguous spread from right liver lobe to lung
pleuropulmonary amebiasis:
entamoeba dx
RBCs?
WBCs?
trophozoites or cysts in poop (3x samples, consecutive)
RBCs present but few
very few WBCs (mostly macros- PMS killed off)
more entamoeba dx
sigmoidoscopy : scraping or biopsy, take from edge of ulcer
ELIXA for Ag
PCR for DNA in stool
liver scan - assoc. systemic leukocytosis
ddx entamoeba
IBD, Crohn’s, anaeorobic parasites
entamoeba tx
metronidazole
newer/better: Tinidazole
entamoebe prevented by
improving sanitation
using condoms
