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Flashcards in GI infections (3) Deck (62):
1

list the GI tract infections we are expected to know

1. C. difficile
2. gastroenteritis/travellers diarrhea
3. rotavirus
4. hepatic abscess
5. H. pylori related infections
6. esophagitis

2

what is the #1 etiologic cause of antibiotic related diarrhea

C. difficile

(96% of C. diff infections are antibiotic related)

3

how is C. difficile transmitted

fecal oral

4

how can a C. difficile infection present

1. asymptomatic colonization
2. mild-moderate diarrhea
3. severe pseudomembranous colitis

5

what is a pseudomembrane

a layer of exudate resembling a membrane, formed on the surface of the skin or a mucous membrane

6

what is pseudomembranous colitis

C. difficile infection

7

what antibiotics can cause C. difficile?

which are the most risky?

all antibiotics can cause C. difficile

most risky = CLINDAMYCIN and CIPROFLOXACIN
(lincosamide and fluoroquinolone)

8

what are the toxins associated with C. diff, and what type of toxin are they

toxin A and toxin B

A = enterotoxin
B=cytotoxin (more potent)

9

how does C. difficle cause disease

colonization of the colonic mucosa--> antibiotic therapy (disruption of normal intestinal flora)-->C. diff releases toxin A and toxin B--> mucosal injury and inflammation--> C. difficile colitis

10

what is the J strain of C. diff

epidemic CLINDAMYCIN RESISTANT strain

11

what is the NAP1/B1/027 strain of C. diff

emergent virulent strain

produces more toxins A and B, have higher recurrence, less clinical cure

FLUOROQUINOLONE resistance

12

how long after Ab Tx does C. diff present

during Ab Tx or within 2 weeks

13

what type of diarrhea does C. diff cause

watery

>3 stools/day

14

describe the clinical presentation of C. diff

watery diarrhea
elevated WBCs
60% have unexplained leukocytosis
low grade fever

15

what is fulminant colitis

can arise as a result of C. diff infection

"toxic megacolon"

abdominal pain, distention, lactic acidosis, hypovolemia, high WBC, may NOT have diarrhea, pseudomembranes

URGENT SURGICAL EVAL

16

Tx of C. diff (protocol)

1. Assess (vital signs, abdo exam, hydration; CBC, chemistry)
2. contact precautions
3. STOP: all possible antibiotics, proton pump inhibitors, all anti-diarrheal agents

17

Tx of C. diff (meds)

1. mild-moderate disease--> METRONIDAZOLE
reassess after 4-6 days and if not improved, add oral VANCOMYCIN

2. severe disease or recurrence--> oral VANCOMYCIN
reassess in 4-6 days and if not better add METRONIDAZOLE


always: monitor patients closely, use ORAL vancomycin, contact GI, ID and surgery in severe disease

18

what % of returning travellers get travellers diarrhea

30-70%

19

is most travellers diarrhea viral or bacterial

bacterial

20

what are the most common etiologic agents of travellers diarrhea

1. ETEC
2. Enteroaggregative E. coli (EAEC)

3. campylobacter jejuni
4. Salmonella spp
5. Shigella spp

21

would you suspect intestinal helminths in a returning traveller with diarrhea?

not usually as most are asymptomatic and wouldn't cause travellers diarrhea as much as a bacterial cause would

22

what would you suspect as the etiologic agent in travellers diarrhea with the following presentations:
1. acute onset
2. gradual onset or chronic low grade diarrhea
3. bloody with fever
4. brief episode of vomiting and diarrhea resolving within 12 hours

1. bacterial or viral
2. protozoa (giardia or entamoeba histolytica)
3. (dysentery) shigella, campylobacter or salmonella
4. ingested toxin (food poisoning)

23

though its usually not necessary to ID the pathogen in traveller's diarrhea, when you need to, how do you do it?

1. stool culture for immunocompromised patients or in outbreaks, or with dysentery presentation--> can ID shigella, campylobacter, salmonella
-CANT distinguish ETEC/EAEC from nonpathogenic E. coli and cant ID viral causes

2. stool microscopy ("ova and parasites")
-for giardia, cyclospora, entamoeba, microsporidia, cryptosporidia
-order for symptoms lasting more than 10 days

3. direct fluorescent antibody (DFA)/ enzyme immunoassay for giardia and cryptosporidium

24

would you or would you not use anti-motility agents with dysentery

NO

use anti motility agents only with Abs

25

what is the leading cause of acute diarrhea in children

rotavirus

responsible for 40% of hospital admissions worldwide

26

what are the largest factors in diarrheal deaths?

unsafe water
inadequate sanitation
poor hygiene

27

where do most diarrhea deaths occur

Africa
South Asia

28

how many rotavirus particles are required for infection

10

29

what is the most common age affected by rotavirus

6-24 months

babies are protected by IgA in breastmilk

30

how do you diagnose rotavirus

ELISA or latex agglutination or PCR

31

how do you treat rotavirus

ORS
Zinc
continued breastfeeding

32

how do you prevent rotavirus

ROTARIX vaccine

2 doses at 2 and 4 months

33

do hepatic abscesses usually present with bowel symptoms

no, often present without

34

what is the most likely organism causing amoebic liver abscess

entamoeba histolytica

(or E. dispar)

35

how do you distinguish between E. histolytica and E. dispar as the cause of an ALA?

their cysts are indistinguishable on microscopy

E. histolytica can have ingested RBCs whereas E. dispar doesn't

E. histolytica have invasive disease (liver, intestine, lung, brain) whereas E. dispar is asymptomatic colonization

36

which is more common in the developed world, ALA or bacterial liver abscess

bacterial

37

what is the source of ALA infection? bacterial liver abscess?

ALA = 100% hematogenous

bacterial = biliary (60%), hematogenous (20%) and other like trauma, iatrogenic, extension

38

what is the aspirate like in ALA? in bacterial?

ALA = brown, no odor, "anchovy paste" quality

bacterial = purulent, green/yellow, foul odor

39

what organisms cause bacterial liver abscesses

1. E. coli
2. Klebsiella
3. Strep
4. enterococcus
5. bacteroides

often polymicrobial

40

what are serology results for ALA? bacterial liver abscecss?

ALA = +
bacterial = -

41

Tx for ALA

1. METRONIDAZOLE
2. paramomycin/iodoquinol

42

Tx for bacterial liver abscess

empiric coverage for enteric GNRs, enterococcus, anaerobes

43

what is the most common cause of gastritis

H. pylori related infections

44

what is the most common chronic bacterial infection in humans

H. pylori related infections

45

what causes 90% of duodenal ulcers

H. pylori

46

how is H. pylori transmitted

fecal-oral and oral-oral

47

what bacteria increases the risk of gastric cancer

H. pylori

48

pathophysiology of H. pylori infections

bacterial UREASE hydrolyzes urea --> NH4

NH4 neutralizes stomach acid

SPIRAL shaped, flagella, and MUCOLYTIC enzymes of H. pylori allow it to "swim" through mucous to epithelium

ADHESINS bind to epithelial receptors

49

who do you test for H. pylori

anyone with:
gastric cancer
active PUD
of Hx of PUD

anyone with symptoms of dyspepsia

50

what tests do you use for H. pylori

1. urease breath test (really sensitive and specific)
2. serology (ELISA, IgG)
3. stool antigen (less accurate)
4. endoscopy and biopsy (for urease, histology and culture)--> do in older patients with "danger signs"

51

Tx of H. pylori

HP-Pac--> Lansoprazole + clarithromycin + amoxicillin (14 days)

20% of pts fail first Tx

52

what is the primary HIV opportunistic infection when CD4 cell count falls below 200

thrush

53

how do you treat oropharyngeal candidiasis

NYSTATIN rinse

clotrimazole troches
ARVs if HIV+
fluconazole

54

what is esophageal candidiasis

esophagitis
usually with thrush
HIV or other immunosuppresion = comorbid

55

Tx of esophageal candidiasis

always SYSTEMIC antifungals

empiric Tx same in immunocompromised as competent

FLUCONAZOLE

echinocandins
amphotericin B

56

what are GI infections usually caused by?

usually due to ingestion of a pathogen or toxin that either localizes to the gut or disseminates beyond

can also be caused by disruption of normal gut flora, gut architecture or host immune system

57

what causes most travellers diarrhea

ETEC or EAEC

usually doesnt require diagnostic tests or antibiotics

58

is liver abscess serious?

YES

it is a serious condition that requires prompt hospitalization, CT scan, empiric Ab therapy to cover ENTERIC GRAM - RODS, ENTEROCOCCUS and ANAEROBES

59

most common cause of bacterial liver abscess

biliary tract obstruction or infection

60

how does most entamoeba present?

usually asymptomatically

61

how does E. histolytica usually present

can be locally invasive and disseminate (i.e ALA)

62

who requires an evaluation for immunosuppresion on presentation with thrush

patients older than 12 months old