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Flashcards in GI Deck (39):
1

Evaluating GI infections/food poisoning

- history and physical
- travel history
- recreational activities
- duration of symptoms

2

Duration of GI symptoms

- acute: < 14 days
- persistant: < 30 days
- chronic: > 30 days

3

GI anatomic considerations

- esophagus to stomach to small intestine to large intestine
- pH of stomach can withstand most bacteria
- peristalsis of small intestine inhibits adherence
- colon flora and IgA compete with pathogens

4

GI risk factors

- number of ingested organisms
- achlorhydia
- reduction in normal flora due to antibiotics

5

Traveler's diarrhea

Enterotoxigenic E. coli

6

Parasitic infections

Giardia, Entamoeba

7

Antibiotic-associated diarrhea

C. difficile

8

Practical diagnosis

- History (food ingestion, travel, activities)
- Duration of illness
- Medications
- Underlying conditions
- Physical exam (state of hydration, exam of abdomen)
- Laboratory studies
- Fecal exam

9

Direct fecal smear

- Gram stain of smear
- WBC's indicate invasion, not toxin

10

Enterotoxin-mediated diarrhea

- rapid onset indicates preformed toxin
- lack of fever
- absence of blood or pus
- large number of watery stools (> 20/day)
- Enterotoxigenic E. coli, cholera, S. aureus, C. perfringens, Bacillus cereus, viral or parasitic

11

Diarrhea mediated by invasion of bowel mucosal surface

- fecal leukocytes, RBC's, fever
- Salmonella, Campy, Shigella, E. coli, Entamoeba

12

Diarrhea mediated by invasion of full thickness of bowel with lymphatic spread

- S. typhi, Y. enterocolitica
- presents with constipation
- fecal leukocytes and RBC's

13

Common viral pathogens

Rodaviruses, Enteric adenoviruses, calciviruses, astroviruses

14

Common bacterial pathogens

Campy, Salmonella, Shigella, E. coli, Vibrio (parahaemolyticus, cholera, vulnificus), Y. enterocolitica, C. difficile, Listeria monocytogenes, Helicobacter, Aeromonas, Plesiomonas shigelloides, Edwardsiella, Neisseria gonorrhoeae, Chlyamydia, Treponema

15

Common parasitic pathogens

Giardia intestinalis, E. histolytica, Cryptosporidium, Cyclospora, Microsporidia

16

- most common cause of diarrheal illness worldwide
- microaerophilic, Campy BAP, 42C
- seagull wing appearance, darting motility
- oxidase +, catalase +

Campylobacter jejuni

17

- contaminated meat, eggs
- symptoms 6-8 hours after ingestion
- usually self-limiting
- indole -, K/A H2S +, oxidase -
- enteric fever
- high inoculum required

Salmonella typhi

18

- dysenteriae, flexneri, boydii, sonnei
- sonnei is most common in US
- non-motile, oxidase -
- causes dynsentery
- low inoculum required

Shigella

19

- infantile diarrhea
- adhesive, mucus in stool (no blood)

Enteropathogenic E. coli

20

- Traveler's diarrhea
- due to poor sanitation
- requires large inoculum
- releases toxins

Enterotoxigenic E. coli

21

- dysentery with direction invasion/destruction of mucosa
- similar to Shigella, but higher inoculum
- watery diarrhea with blood, mucus and WBCs

Enteroinvasive E. coli

22

- rice-water stool
- large loss of electrolytes
- associated with epidemics
- catalase +, oxidase +
- toxin produced
- yellow on TCBS

Vibrio cholera

23

- Summer diarrhea in Japan, associated with seafood
- diarrhea and cramping
- green on TCBS

Vibrio parahaemolyticus

24

- "lactose positive" species
- raw or undercooked seafood, wounds
- green on TCBS

Vibrio vulnificus

25

- grows at 4C, can go septic
- meat, unpasteurized milk, dairy products
- CIN agar (target growth)
- K/A, ODC +, non-motile
- self-limiting, possible invasion of mesenteric lymph nodes
- sometimes mistaken for appendicitis

Yersinia enterocolitica

26

- sometimes normally in intestines
- antibiotic-associated diarrhea
- pseudomembranous colitis
- mild to severe disease

Clostridium difficile

27

- deli meat
- grows at cold temps
- CAMP +, catalase +, tumbling motility
- premature labor, spontaneous abortion

Listeria monocytogenes

28

- peptic ulcers
- stomach cancer
- urease +, Christensen's urea medium, urea breath test
- cinaedi and fennelliae associated with diarrhea

Helicobacter pylori

29

STD's causing GI infections

- cause proctitis with lose stools and pain on defecation
- N. gonorrhoeae, Chlamydia, Treponema

30

Toxic agents of Food Poisoning (chemical)

- scombroid: flushing, headache, crampy abdominal, tissue of fish
- Ciguatera: red tide toxin buildup in fish, diarrhea, weakness, abdominal pain
- Tetrodotoxin: puffer fish toxin (death in 50%)

31

GI Infections in ICPs

- AIDS, cancer, transplants patients
- high risk for opportunistic infections
- Bacteria: Mycobacteria membrane attack complex
- Virus: CMV
- Parasites: Crypto, etc.

32

GI Infection (lab diagnosis)

- fresh specimen is best for culture
- Direct microscopic exam: look for fecal leukocytes, RBC's, seagull wing/curved appearance of Campy and Vibrio
- streak to SBA, MAC, Choc, SMAC, HE, XLD, Campy agar, CIN, TCBS, CCFA

33

HE plate

- Salmonella shows H2S (black colonies)
- Shigella has no H2S

34

SMAC

E. coli O157:H7 doesn't ferment sorbitol

35

Campy agar

selective for Campylobacter jejuni

36

CIN agar (cefsulodin- Igrasan-novobiocin)

selective for Yersinia enterocolitica (target/bulls-eye growth)

37

TCBS agar

- Vibrio cholera and alginolyticus utilize sucrose (turn yellow)
- Vibrio vulnificus and parahaemolyticus don't utilize sucrose

38

CCFA agar

selective for C. difficile (pale yellow colonies - fluoresce bright yellow)

39

Diarrhea treatment and prevention

- replenish electrolytes (IV fluids if necessary)
- antidiarrheal medications (not for invasive diarrhea)
- antibiotics to treat infection