GI Infections 5

Question 1

if the patient is only positive for the antibodies to HBs antigen, it is indicative of ______

Answer 1

vaccinated against HBV

Question 2

what are some incriminated foods for contamination by the B. cereus emetic toxin

Answer 2

rice

Question 3

_______ has a bacteriophage encoded enterotoxin

Answer 3

Vibrio cholera

Question 4

what are some common pathogens in the Enterobacteriaceae family?

Answer 4

• E. coli
• Shigella
• Salmonella
• Yersinia
• Klebsiella
• Proteus

Question 5

pt. has negative surface antigen positive antibodies for surface antigen and has positive iGG for HBc

Answer 5

previous exposure

Question 6

vibrio cholera has a ______ encoded enterotoxin

Answer 6

bacteriophage

Question 7

_________ is an E. coli plasmid encoded enterotoxin that has similar function as that of the Cholera toxin

Answer 7

LT enterotoxin

cholera = activates adenylate cyclase

Question 8

the B subunit binds to ______ on the cell surface

Answer 8

GM1 receptor

Question 9

what is the difference between the enterotoxin released by E. coli and that released by Vibrio cholera?

Answer 9

• both cause watery diarrhea
• both are AB enterotoxins that bind to GM1 receptor
• E. coli is PLASMID encoded
• Vibrio cholera is BACTERIOPHAGE encoded

Question 10

which E. coli strain does NOT have LT or ST or CFA? how does it cause watery diarrhea?

Answer 10

• EPEC (enteropathogenic)

- via effacement of the microvilli in the SI

Question 11

incubation period of someone who just ingested a preformed exotoxin in food:

Answer 11

within hours of eating the food

Question 12

why is ingestion of antacids a risk factor for developing vibrio cholera infection?

Answer 12

vibrio cholera is acid sensitive so by ↑ the pH of the stomach, then it makes it more likely for the bacteria to survive

Question 13

describe the structure of the enterotoxins released by E. coli and how they attach

Answer 13

it is a 1A5B toxin (5 peripheral B subunits all attached to one central A subunit)
B subunit binds to GM1 receptor and the A subunit enters the cell and causes the ↑ in cAMP or cGMP

Question 14

clostridium perfringens is associated with _________ (food)

Answer 14

meat dishes/gravy that have been left out after being heated

Question 15

Vibrio Cholera is oxidase _______

Answer 15

POSITIVE (E. coli is oxidase negative)

Question 16

after adhesion, E. coli releases two plasmid-encoded _________:

Answer 16

enterotoxins:
LT: activates adenylate cyclase (similar to cholera)
ST: activates guanylate cyclase

Question 17

vibrio cholera is a +/- sucrose fermenter

Answer 17

+

Question 18

what is the mechanism of the ST (heat stable) enterotoxin released by E. coli?

Answer 18

• activates guanylate cyclase

Question 19

what is the difference between C. perfringens and B. cereus in terms of enterotoxin production

Answer 19

• C. perfringens only produces the toxins once it is inside the SI
• B. cereus can produce the toxin while in the food so you can ingest the toxin but not for C. perfringens

Question 20

the cholera toxin is similar to the ______ enterotoxin of E. coli

Answer 20

LT (↑ cAMP)

Question 21

what kind of enterotoxin is produced by C. perfringens?

Answer 21

LT (CPE)

Question 22

what are some unique features of EPEC?

Answer 22

EPEC does NOT have ST or LT or CFA

EPEC has a large adherence factor plasmid that encodes for bundle forming pili

Question 23

describe the biology of clostridium perfringens

Answer 23

• gram postive
• large anaerobes
• non motile
• ubiquitous in nature
• spore forming

Question 24

E. coli has a ________ encoded enterotoxin

Answer 24

plasmid

Question 25

what is the mechanism of the cause of non inflammatory diarrhea

Answer 25

colonization and release of enterotoxin in SI

Question 26

what is the cause of the emetic type of bacillus cereus infection

Answer 26

ingestion of food containing PREFORMED ST NEUROTOXIN

Question 27

the H antigen in E. coli makes up the ______

Answer 27

subunits of the bacterial flagella

Question 28

gram negative rod that ferments sucrose and mannose but NOT arabinose

Answer 28

Vibrio cholera

Question 29

how does EPEC colonize and adhere to the SI when it does not have CFA?

Answer 29

EPEC strains carry a large EPEC adherence factor plasmid that encodes bundle forming pili (BFP) then it effaces the microvilli → loss absorptive surface → watery diarrhea

Question 30

``` describe the biology of E. coli catalase: oxidase: agar: does it ferment lactose? ```

Answer 30

- gram negative bacilli - facultative anaerobe - member of normal (commensal) intestinal flora - catalase positive - oxidase negative - lactose fermenter - grown on MacConkey agar

Question 31

how does C. perfringens cause watery diarrhea?

Answer 31

- sporulation in the SI - release of CPE (C. per fringes enterotoxin/ LT) - cytotoxic activity in which there is pore formation in the membrane

Question 32

metabolic ________ is a common result of diarrhea

Answer 32

acidosis due to the loss of HCO3

Question 33

__________ is a bacteria that has cytotoxic activity and causes pore formation leading to watery diarrhea

Answer 33

C. perfringens

Question 34

describe the biology of Vibrio cholera motile? spore forming? oxidase activity?

Answer 34

- single curved gram NEGATIVE rods - "s" shaped - motile with a single polar flagellum - non spore forming - oxidase POSITIVE

Question 35

which E. coli strain is also known as "infantile diarrhea"

Answer 35

EPEC ePec: Pediatrics

Question 36

what is a screening method for cholera in stool samples?

Answer 36

- look for oxidase activity because E. coli does not have oxidase activity while Cholera does

Question 37

TCBS agar is used for what pathogen?

Answer 37

Vibrio cholera

Question 38

_____ is grown in MacConkey agar

Answer 38

E. coli | it is a selective media

Question 39

strains of Vibrio cholera are classified based on ______

Answer 39

O and H antigens | O1 and O139 are most important

Question 40

describe the biology of bacillus cereus

Answer 40

gram positive arranged in chains aerobic has both emetic toxin and enterotoxin

Question 41

where can you find bacillus cereus

Answer 41

air, soil, water, and dust

Question 42

which species of E. coli is the #1 cause of traveller's diarrhea?

Answer 42

- ETEC (enterotoxigenic E Coli)

Question 43

how does E. coli attach to and colonize the SI?

Answer 43

-CFA: colonization factor antigens = fimbrae

Question 44

what is the neurotoxin that is ingested from contaminated rice in ______ infection

Answer 44

ST neurotoxin in B. cereus infection causing emesis

Question 45

Vibrio cholera can be grown on _________ agar with ______ as the differentiating agent

Answer 45

- thiosulfphate citrate bile salts sucrose (TCBS) agar | - SUCROSE is the differentiating agent → yellow color because cholera ferments sucrose

Question 46

viral infection usually causes ______ diarrhea

Answer 46

non inflammatory

Question 47

bundle forming pili is a virulence factor for _____

Answer 47

EPEC

Question 48

what is the diarrhea enterotoxin in bacillus cereus

Answer 48

LT (↑ cAMP)

Question 49

fecal leukocytes are NOT found in inflammatory/noninflammatory diarrhea

Answer 49

non inflammatory diarrhea