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Flashcards in Diarrheas presenting +/- fever Deck (55):
1

Shiga(Vero)-Toxin E. Coli (STEC) includes ??

FYI: Shiga toxin (Stx) = Verotoxin

EHEC: Enterohemorrhagic E. coli O157:H7 (the only sorbitol-negative STEC)

2

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)

3

Plotkin's EHEC scenario

petting zoo-->bloody diarrhea-->given abx-->exacerbated!-->needs dialysis bc of renal failure-->tonic clonic seizures-->HUS

4

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

5

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

6

VTEC cases in US: strains?

O157:H7 (known as EHEC)
also O111
>100 ww that cause HUS

7

German outbreak

O104:H4 in bean sprouts
new type of STEC: combo of EAEC and Stx production

8

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

9

EHEC affects who ??

kiddos and oldies more affected

10

EHEC seasonality
risks

summer, risk for under grilled hamburgs
unpast. juices, milk, bean sprouts, poor personal hygiene

11

EHEC duration
but young kiddos may still poop org out for..

may resolve in 5-10 days
up to 2 weeks!

12

STEC/EHEC virulence factors

pili: adherence
Shiga toxin (Stx) production

13

ingested EHEC adheres to ?? and then ??

colonic mucosa
produces Stx

14

main targets of Stx

gut, kidney, brain
-->produces HUS if gets into circulation (5-10% pts)

15

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)

16

why can some EHEC strains cause HUS ??

able to adhere more tightly to intestinal mucosa

17

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

18

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*

19

EHEC dx

routine bac Cx on sorbitol-containing medium
assay for Shiga toxins (ID STEC)
Cx on MacConkey agar with sorbitol (not lactose)

20

EHEC on MacConkey agar

will be WHITE: sorbitol negative (other STECs and EAEC are sorbitol postitive-pink)

21

confirm EHEC dx with

serotyping (O157:H7)
ELISA for Stx in poop
PCR (alternative)

22

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

23

EHEC tx

supportive tx ONLY
abx do not shorten course and may inc. risk for HUS

24

if HUS happens and no Stx ??

defect in alternative complement pathway

25

ddx HUS

acute abdomen
acute gastroenteritis
aapendicitis
colitis
DIC
IBD
intussucsception
lupus
TTP
pancreatitis
chemo agents: mitomycin, cisplatin, bleomycin, gemcitabine

26

entamoeba histolytica

invasive eukaryotic protozoan
trophozoite: lack mitochondria, anaerobe, needs large amounts of iron to survive

27

entamoeba ?? to in order to survive

ingest RBCs

28

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

29

entamoeba infectious form
survives where?

cyst
can survive in moist soil or water >1 wk
not killed by normal levels of chlorine

30

entamoeba can be killed by..

boiling, desiccation, light, heat, 200 ppm iodine

31

entamoeba occurs where? in who??

developing countries
US: immigrants, travelers, oral-anal sex

32

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

33

entamoeba age, gender, seasonality assoc.

NONE

34

entamoeba risk factors

low SES
travel to endemic areas
closed populations
promiscuitey

35

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

36

entamoeba ??? adhere to colonic epithelium via this virulence factor

trophozoites
adhesins

37

entamoeba invade the epithelium via ?? and proceed ??

soluble cytotoxins: EC proteases that degrade elastase and collagen
proceed laterally cell-to-cell

38

entamoeba: cell destruction occurs with formation of ?? surrounded by ?? (which implies what)

discrete ulcers "flasks"
normal appearing intestinal mucosa, suggesting little/no inflammation

39

entamoeba soluble cytotoxins also ?? which is responsible for the lack of inflammation and few WBCs in feces

kill PMNS on contact

40

entamoeba virulence factors that degrades C3a and C5a

cysteine protease

41

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)

42

entamoeba vir fax: monocyte locomotion inhibition factor

inhibits monocyte migration and blocks respiratory burst of both macros and PMNs

43

entamoeba presentation
fever?

diffuse abd. pain, profuse bloody diarrhea (wide variation)
with or without fever

44

>75% have this if entamoeba inf left untx ??

liver abscess and colonic perforation

45

duration of entamoeba if left untx?

>3 wks
wl, abd pain

46

acute amoebic colitis


fever?

bloody diarrhea, loose, intermittent, watery stool
abd. pain RLQ, abd. tenderness, urgency to defecate

33% have fever and constitutional symptoms

47

fulminant colitis seen in who?
prevalence of entamoeba cases ?

uncommon presentation seen most in kiddos
3-4%

48

ameboma (entamoeba) occurs in 1% of those with ??
presents as a ?? and does not respond well to ??

intestinal disease
mass lesion
antiparasite therapy

49

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

50

most frequent complication of amebic liver abscess (extraintestinal amebiasis) ???
via contiguous spread from right liver lobe to lung

pleuropulmonary amebiasis:

51

entamoeba dx
RBCs?
WBCs?

trophozoites or *cysts* in poop (3x samples, consecutive)
RBCs present but few
very few WBCs (mostly macros- PMS killed off)

52

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

53

ddx entamoeba

IBD, Crohn's, anaeorobic parasites

54

entamoeba tx

metronidazole
newer/better: Tinidazole

55

entamoebe prevented by

improving sanitation
using condoms

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