GI

Question 1

Evaluating GI infections/food poisoning

Answer 1

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

Question 2

Duration of GI symptoms

Answer 2

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

Question 3

GI anatomic considerations

Answer 3

• 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

Question 4

GI risk factors

Answer 4

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

Question 5

Traveler’s diarrhea

Answer 5

Enterotoxigenic E. coli

Question 6

Parasitic infections

Answer 6

Giardia, Entamoeba

Question 7

Antibiotic-associated diarrhea

Answer 7

C. difficile

Question 8

Practical diagnosis

Answer 8

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

Question 9

Direct fecal smear

Answer 9

• Gram stain of smear

- WBC’s indicate invasion, not toxin

Question 10

Enterotoxin-mediated diarrhea

Answer 10

• 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

Question 11

Diarrhea mediated by invasion of bowel mucosal surface

Answer 11

• fecal leukocytes, RBC’s, fever

- Salmonella, Campy, Shigella, E. coli, Entamoeba

Question 12

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

Answer 12

• S. typhi, Y. enterocolitica
• presents with constipation
• fecal leukocytes and RBC’s

Question 13

Common viral pathogens

Answer 13

Rodaviruses, Enteric adenoviruses, calciviruses, astroviruses

Question 14

Common bacterial pathogens

Answer 14

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

Question 15

Common parasitic pathogens

Answer 15

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

Question 16

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

Answer 16

Campylobacter jejuni

Question 17

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

Answer 17

Salmonella typhi

Question 18

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

Answer 18

Shigella

Question 19

• infantile diarrhea

- adhesive, mucus in stool (no blood)

Answer 19

Enteropathogenic E. coli

Question 20

• Traveler’s diarrhea
• due to poor sanitation
• requires large inoculum
• releases toxins

Answer 20

Enterotoxigenic E. coli

Question 21

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

Answer 21

Enteroinvasive E. coli

Question 22

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

Answer 22

Vibrio cholera

Question 23

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

Answer 23

Vibrio parahaemolyticus

Question 24

• “lactose positive” species
• raw or undercooked seafood, wounds
• green on TCBS

Answer 24

Vibrio vulnificus

Question 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

Answer 25

Yersinia enterocolitica

Question 26

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

Answer 26

Clostridium difficile

Question 27

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

Answer 27

Listeria monocytogenes

Question 28

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

Answer 28

Helicobacter pylori

Question 29

STD's causing GI infections

Answer 29

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

Question 30

Toxic agents of Food Poisoning (chemical)

Answer 30

- 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%)

Question 31

GI Infections in ICPs

Answer 31

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

Question 32

GI Infection (lab diagnosis)

Answer 32

- 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

Question 33

HE plate

Answer 33

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

Question 34

SMAC

Answer 34

E. coli O157:H7 doesn't ferment sorbitol

Question 35

Campy agar

Answer 35

selective for Campylobacter jejuni

Question 36

CIN agar (cefsulodin- Igrasan-novobiocin)

Answer 36

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

Question 37

TCBS agar

Answer 37

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

Question 38

CCFA agar

Answer 38

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

Question 39

Diarrhea treatment and prevention

Answer 39

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