GI 2

Question 1

macconkey agar

Answer 1

lactose fermentation
positive=red
negative = white

Question 2

e.coli on macconkey agar

Answer 2

positive red

Question 3

salmonella or shigella on macconkey agar

Answer 3

negative white

Question 4

positive indole test

Answer 4

red color change (indole production)

Question 5

negative indole test

Answer 5

no color change (no indole production)

Question 6

e.coli or vibrio spp. on indole test

Answer 6

positive red color change

Question 7

salmonella on indole test

Answer 7

negative no color change

Question 8

black precipitate

Answer 8

hydrogen sulfite production

Question 9

salmonella v. shigella

Answer 9

salmonella= black precipitate

shigella = no precipitate

Question 10

• gram negative faculative anaerobe
• moderately invasive
• watery diarrhea
• pediatric diarrhea in developing countries

Answer 10

EPEC

Question 11

virulence of EPEC

Answer 11

• no toxins
• BfpA bundle forming pilus
• Type III secretion system

Question 12

pathogenesis of EPEC

Answer 12

• bac injects Type III secretion
  “attaching and effacing”
  system prtns directly into host cells
• bac produced intimin binds to Tir and creates tight interaction
• F actin polymerization causes a loss of brush border ( less absorption of liquid –> diarrhea)

Question 13

lactose positive indole positive

Answer 13

e. coli, use PCR to determine which type

Question 14

• gram negative
• faculative anaerobe
• non-invasice
• travelers’s diarrhea
• diarrhea in children in developing world

Answer 14

ETEC

“t for travelers”

Question 15

virulence factors for ETEC

Answer 15

• fimbriae
• LT heat liable toxin
• ST heat stable toxin
• plasmid encoded

Question 16

pathogenesis of ETEC

Answer 16

• adherence to the cell with fimbriae/pili produces two toxins LT and ST
• LT finds it way to activate adenylate cyclase and increase cAMP –> efflux of electrolytes and water follows (diarrhea)
• ST increase cGMP and same efflux of water and electrolytes

Question 17

diagnosis of ETEC

Answer 17

• clinical history

- DNA probe to detect LT and ST encoding gene

Question 18

full name of s. typhi

Answer 18

salmonella enterica serovar typhi

Question 19

is salmonella inflammatory?

Answer 19

yes!

Question 20

• gram negative faculative anaerobe
• motile rods, flagellated (h antigen)
• acid tolearant
• intracellular pathogen

Answer 20

salmonella typhi

Question 21

reservoir of salmonella typhi

Answer 21

humans

Question 22

infectious dose of salmonella typhi

Answer 22

10tothe5th - 10tothe6th

• survive only in high number because acid tolerant, not resistant

Question 23

• fever with headache
• rising fever over 3 days
• typhoid fever
• followed by GI symptoms

Answer 23

salmonella typhi

Question 24

where does salmonella typhi chronically colonize

Answer 24

gall bladder

Question 25

pathogenesis of salmonella typhi

Answer 25

- adherence to Mcells and enterocytes - type III secretion system mediated uptake into M cell (macrophage) with membrane ruffling - escape macrophage and cause bacteremia

Question 26

diagnosis of salmonella typhi

Answer 26

culture of stool and blood samples on selective media

Question 27

treatment of salmonella typhi

Answer 27

antibiotic therapy with fluroquinolones, trimethoprim-sulfamethoxazole or broad spectrum cephlosporin

Question 28

prevention salmonella typhi

Answer 28

- drink only bottled water, thoroughly cooked food avoid raw frutis and vegetables - vaccination for travelers (capsule or injection)

Question 29

differences between s. typhi and nontyphoidal salmonella

Answer 29

same, but nontyphoidal is not as human adapted

Question 30

- symptoms 6-48 h post ingestion - nausea and vomiting followed by abdominal cramps and watery diarrhea - perisistent diarrhea for 3-4 days - 50% fever

Answer 30

nontyphoidal salmonella

Question 31

how is pathogenesis of non-typhoidal salmonella different than s. typhi?

Answer 31

after entry into macrophages there are 2 scenarios - rapid killing of macrophage which confines the infection and causes diarrhea - carriage in macrophage (immunocompromised) leading to systemic dissemination

Question 32

how does a culture of nontyphoidal salmonella appear?

Answer 32

``` non-lactose fermenting (white on MacConkeys) produces H2S (black precipitate) ```

Question 33

treatment salmonella gastroenteritis from non-typhoidal salmonella

Answer 33

``` electrolyte replacement NOT antibiotics (enhances carrier state) ```

Question 34

nontyphidal salmonella systemic infection treatment

Answer 34

anitbiotic therapy

Question 35

gram-negative rod, curved or 'sea-gull shaped' - microaerophilic - invasive

Answer 35

campylobacter jejuni

Question 36

ulceration and acute enteritis water diarrhea sepsis guiliain-barre sequelae

Answer 36

campylobacter jejuni

Question 37

acute immune mediated polyneuropathy | -progressive fairly symmetric muscle weakness accompained by absent or depressed deep tendon refleces

Answer 37

guillain-barre syndrome

Question 38

diagnosis campylobacter jejuni

Answer 38

selctive media in a microaerophilic environment

Question 39

treatment campylobacter jejuni

Answer 39

supportive | antibiotic if severe with microlide